Attachment 2 - 2024 Amended Eastern San Joaquin Groundwater Sustainability Plan — Manteca City Council, April 15, 2025 (part 5 of 6)

ESJWRM)
Export out of
model (imported
in Diversions 53,
54, 56, and 58)
Ag 0% 0% 0% 136,900 121,000 OID
ATTACHMENT 2
Eastern San Joaquin Groundwater Authority 36 Woodard & Curran, Inc.

ESJWRM)
Export out of
model (imported
in Diversions 59,
60, and 61)
Ag 0% 0% 0% 187,900 150,000 SSJID
31 Stanislaus River to
Woodward Reservoir
to South San Joaquin
ID Division 6 for Ag
Import
(outside of

ESJWRM)
Export out of
model (imported
in Diversions 59,
60, and 61)
Ag 0% 0% 0% 5,300 7,000 SSJID
32 Woodward Reservoir
Seepage
Import
(outside of

ESJWRM)
Woodward
Reservoir Recharge 100% 0% 0% 17,100 16,000 SSJID
33 Stanislaus River to
Woodward Reservoir
to Nick C. DeGroot
WTP to City of
Manteca for M&I
Import
(outside of

ESJWRM)
City of Manteca Urban 0% 0% 100% 7,000 11,000 UWMP
34 Stanislaus River to
Woodward Reservoir
to Nick C. DeGroot
WTP to City of
Escalon for M&I
Import
(outside of

ESJWRM)
City of Escalon Urban 0% 0% 100% 0 0 UWMP
35 Stanislaus River to
Woodward Reservoir
to Nick C. DeGroot
WTP to City of
Lathrop for M&I
[Tracy Subbasin]
Import
(outside of

ESJWRM)
City of Lathrop Urban 0% 0% 100% 1,700 6,000 UWMP
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ESJWRM)
City of Ripon Urban 0% 0% 100% 0 0 UWMP
37 Tuolumne River to
Modesto ID for Ag
[Modesto Subbasin]
Import
(outside of

ESJWRM)
Modesto ID Ag 3% 19% 78% 229,900 194,000
Stanislaus
River Basin
Plan
ESJWRM
Update
38 Tuolumne River to
City of Modesto (via
Modesto ID) for M&I
[Modesto Subbasin]
Import
(outside of

ESJWRM)
Element group
representing City
of Modesto
Urban 3% 1% 96% 30,500 27,000
Stanislaus
River Basin
Plan
ESJWRM
Update
39 Cosumnes River to
Riparian for Ag
[Cosumnes Subbasin]
Cosumnes
River
Riparian diverters
along river Ag 10% 2% 88% 2,700 2,000 C2VSim
40 Dry Creek to Riparian
for Ag [Split Across
Subbasins]
Dry Creek Riparian diverters
along river Ag 10% 2% 88% 5,800 6,000 C2VSim
41 Mokelumne River to
Riparian for Ag
Mokelumne
River
Riparian diverters
along river Ag 10% 2% 88% 9,800 11,000 C2VSim
42 Calaveras River to
Riparian for Ag
Calaveras
River
Riparian diverters
along river Ag 10% 2% 88% 11,400 11,000 C2VSim
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ESJWRM)
Modesto ID Ag 0% 0% 100% 22,300 24,000
Stanislaus
River Basin
Plan
ESJWRM
Update
47 Tuolumne River to
Modesto Reservoir
Seepage [Modesto
Subbasin]
Import
(outside of

ESJWRM)
Modesto
Reservoir Recharge 100% 0% 0% 23,000 23,000
Stanislaus
River Basin
Plan
ESJWRM
Update
48 City of Modesto GW
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of

ESJWRM)
City of Modesto Urban 3% 1% 96% 33,000 32,000
Stanislaus
River Basin
Plan
ESJWRM
Update
49 City of Oakdale GW
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of

ESJWRM)
City of Oakdale Urban 3% 1% 96% 4,700 5,000
Stanislaus
River Basin
Plan
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ESJWRM)
City of Waterford Urban 3% 1% 96% 1,600 1,000
Stanislaus
River Basin
Plan
ESJWRM
Update
51 City of Riverbank GW
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of

ESJWRM)
City of Riverbank Urban 3% 1% 96% 4,500 4,000
Stanislaus
River Basin
Plan
ESJWRM
Update
52 Farm Deliveries to
Oakdale ID North for
Ag
Import
(exported in
Diversion 28)
Oakdale ID in ESJ
Subbasin Ag 0% 0% 100% 78,700 74,000 OID AWMP
53 Farm Deliveries to
Oakdale ID South for
Ag [Modesto
Subbasin]
Import
(exported in
Diversion 29)
Oakdale ID in
Modesto
Subbasin
Ag 0% 0% 100% 121,500 114,000 OID AWMP
54 Recycled Water to
Oakdale ID South for
Ag [Modesto
Subbasin]
Import
(exported in
Diversion 29)
Oakdale ID in
Modesto
Subbasin
Ag 0% 0% 100% 3,300 3,000 OID AWMP
55 Deliveries to Annual
Contracts by Oakdale
ID North for Ag
Import
(exported in
Diversion 28)
Oakdale ID in ESJ
Subbasin Ag 0% 0% 100% 2,300 3,000 OID AWMP
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ESJWRM Version 3.0 October 2024
ID Description Diversion
Location Delivery Area Primary Use
Fraction
Historical
ESJWRM
Version 3.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 3.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
56 Deliveries to Annual
Contracts by Oakdale
ID South for Ag
[Modesto Subbasin]
Import
(exported in
Diversion 29)
Oakdale ID in
Modesto
Subbasin
Ag 0% 0% 100% 2,200 2,000 OID AWMP
57 Canal and Drain
Seepage in Oakdale
ID North
Import
(exported in
Diversion 28)
Oakdale ID in ESJ
Subbasin Recharge 100% 0% 0% 17,800 18,000 OID AWMP
58 Canal and Drain
Seepage in Oakdale
ID South [Modesto
Subbasin]
Import
(exported in
Diversion 29)
Oakdale ID in
Modesto
Subbasin
Recharge 100% 0% 0% 18,500 18,000 OID AWMP
59 Farm Deliveries to
South San Joaquin ID
for Ag
Import
(exported in
Diversions 30
and 31)
South San
Joaquin ID Ag 0% 0% 100% 142,500 120,000 SSJID
AWMP
60 Direct Diversion from
Main Distributary
Canal to South San
Joaquin ID for Ag
Import
(exported in
Diversions 30
and 31)
South San
Joaquin ID Ag 0% 0% 100% 1,400 0 SSJID
AWMP
61 Main Distributary
Canal and Lateral
Seepage in South San
Joaquin ID
Import
(exported in
Diversions 30
and 31)
South San
Joaquin ID Recharge 90% 10% 0% 33,200 28,000 SSJID
AWMP
62 Mokelumne River to
North San Joaquin
WCD South System
Recharge
Mokelumne
River
North San
Joaquin WCD
South System
Recharge 100% 0% 0% 860 2,000 NSJWCD
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ESJWRM)
Farmington
Reservoir Recharge 100% 0% 0% 570 500 USACE
*RL = Recoverable Loss (canal seepage or recharge)
**NL = Non-Recoverable Loss (evaporation)
*** Averages calculated only for years with diversions occurring (i.e., non-zero average) ATTACHMENT 2
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ESJWRM Version 3.0 October 2024

3.3.10 Groundwater Pumping
Groundwater pumping within ESJWRM is separated into well or distributed pumping. The former largely includes district-operated wells that provide irrigation water through district conveyance canals and laterals along with surface water supplies, while the latter includes estimated private groundwater pumping by individual land owners and pumpers; the locations of which are not available and so are spatially distributed throughout the agricultural and rural areas.

Additional agency wells were added during GSP Annual Report data requests to Cal Water for urban, Manteca for urban, Manteca for ag, and SSJID for ag. There were no further updates to well pumping for Historical ESJWRM Version 3.0. Table 5 lists the number of wells by type and agency included in ESJWRM.

Distributed pumping is estimated by IWFM within the model simulation for each element. There were no changes made to distributed pumping in Historical ESJWRM Version 3.0.

Table 5: Summary of ESJWRM Well Pumping in Historical ESJWRM Version 3.0 Agency
Number
of Urban
Pumping
Wells
Number of
Agricultural
Pumping
Wells
Average
Annual
Urban
Pumping
(acre-feet)
Average
Annual
Agricultural
Pumping
(acre-feet)
Cal Water 57 --- 7,600 0
Escalon 4 --- 1,500 0
Lathrop 6 --- 2,300 0
Linden County WD 4 --- 430 0
Lockeford CSD 4 --- 500 0
Lodi 29 --- 13,100 0
Manteca 16 32 9,100 1,300
Oakdale ID* --- 26 0 6,200
Ripon 9 9 3,900 1,000
SEWD 5 --- 1,300** 0
SSJID --- 29 0 5,300
Stockton 37 --- 8,000 0
Other Modesto
Subbasin Wells --- 246 0 68,600
Total Average Annual Pumping (acre-feet) 48,640 82,200
* Includes wells located both in ESJ Subbasin and Modesto Subbasin ** Average only when wells were active (WY 2015-2023)

3.3.11 Agricultural Operations
Factors that apply to the agricultural operations represented in the model include agricultural return flow fractions, agricultural reuse fractions, and target soil moisture content.

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ESJWRM Version 3.0 October 2024
In Historical ESJWRM Version 2.2, the target soil moisture specifies the fraction of field capacity that IWFM uses to iteratively adjust demand and was updated for the beginning of irrigation season for each crop’s irrigation period and for the end of season in October for vineyards. The minimum soil moisture was adjusted for all crops during the Historical ESJWRM Version 2.2 update.

Canal and drain seepage for agricultural agencies is included in surface water diversion information and discussed in Section 3.2.9 above. The Historical ESJWRM Version 3.0 strives to represent agricultural operations as realistically as possible by working with local agricultural agencies for better understanding of processes. Files that control agricultural operations were extended through water year 2023 by repeating the recent historical data.

3.4 Calibration Updates and Results
The goals of model calibration are (1) to achieve a reasonable water budget for each component of the hydrologic cycle modeled (i.e., land and water use, soil moisture, stream flow, and groundwater) and (2) to maximize the agreement between simulated and observed groundwater levels at selected well locations and simulated and observed streamflow hydrographs at selected gaging stations. These objectives are achieved through verification of the model input data and adjustment of model parameters.

Due to uncertainty in the model initial conditions, a one year “ramp up” period is included to allow groundwater levels to stabilize. Thus, the model calibration period for the ESJWRM is October 1995 through September 2023 or water years 1996 through 2023 (28 years).

3.4.1 Calibration Process
Model calibration begins after data analysis and input data file development is completed. The calibration effort can be broken down into subsets that align with packages within the IWFM platform. As an integrated groundwater model, the results of each part of the simulation are dependent on one another. The model calibration can be considered a systematic process that includes the following activities:
• Collect data and set calibration targets
• Calibrate land and water use
• Calibrate groundwater system
• Calibrate stream system
• Refine groundwater level calibration using PEST
• Perform sensitivity analysis
• Conduct additional refinements to model as necessary

3.4.1.1 Agricultural Demand Adjustment
As part of the calibration of the land and water use budget, root zone parameters are adjusted as needed to achieve reasonable estimates of agricultural demand and to develop the components of a balanced root zone budget. Demand adjustment serves as the foundation of the IWFM calibration for agricultural areas, as estimated demand often translates directly to groundwater pumping, which is the primary stress on the groundwater system. To adjust agricultural demand, element-level root zone parameters, particularly the soil hydraulic conductivity, were adjusted in accordance with the hydrologic soil group and area of the ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
model. Soil hydraulic conductivity was adjusted in the areas of the model to better match reported groundwater pumping, demand, and per unit water use as reported in agricultural water management plans (AWMP) or other reports by various agencies, including OID, SSJID, and NSJWCD.

3.4.2 Aquifer Calibration Verification
Aquifer parameter calibration of ESJWRM utilized a parametric grid covering the model area that reflected the scale at which parameters were adjusted throughout the calibration process. The parametric grid, originally adopted from DWR’s California Central Valley Groundwater-Surface Water Simulation Model with coarse grid (C2VSimCG) nodes, was slightly modified to cover the entire ESJWRM model along the boundaries and additional nodes were added or moved within areas of the model to provide better control.

Aquifer parameters included in ESJWRM are horizontal hydraulic conductivity, vertical hydraulic conductivity, specific storage, and specific yield.

ESJWRM was calibrated to local data and information, surface water flows, groundwater hydrographs, and groundwater contours. The sources used to check model results include local knowledge, agricultural water management plans, urban water management plans, other local planning efforts, measured groundwater levels, and observed streamflow data.

The goal of groundwater level calibration is to achieve the maximum agreement between simulated and observed groundwater elevations at calibration wells while maintaining reasonable values for aquifer parameters. Calibration wells remained the same as for Historical ESJWRM Version 2.0.

Simulated groundwater levels are calibrated to observed levels through adjustments to hydrogeologic parameters or aquifer parameters including hydraulic conductivity, specific storage, and specific yield. Upon model update, the model calibration was verified using the pre-update hydrogeologic aquifer parameters.

As a result of model updates in Historical ESJWRM Version 3.0, a limited number of model parameters were adjusted, including vertical hydraulic conductivity, to accommodate the more reasonable vertical movement of groundwater for the new Layer 1 and Layer 2.

The results of the groundwater level calibration indicate that the ESJWRM reasonably simulates the longterm hydrologic responses under various hydrologic conditions. Figure 13 shows a selection of calibration wells with their resulting groundwater level hydrographs showing the updated calibration of Historical ESJWRM Version 3.0
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ESJWRM Version 3.0 October 2024
Figure 13: Groundwater Level Calibration of Historical ESJWRM Version 3.0 ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
The ESJWRM calibration status was measured using two metrics: the groundwater level trend and the relationship between simulated and observed groundwater levels. The statistics were evaluated to meet the American Standard Testing Method (ASTM) standard. In addition to quantifiable metrics, the ESJWRM calibration was evaluated by generating reasonable regional groundwater flow directions and producing realistic water budgets.

The “Standard Guide for Calibrating a Groundwater Flow Model Application” (ASTM D5981) states that “the acceptable residual should be a small fraction of the head difference between the highest and lowest heads across the site.” The residual is defined as the simulated head minus the observed head. An analysis of all calibration water levels within the model indicated the presence of 200+ feet of water level changes. Using 10 percent as the “small fraction”, the acceptable residual level would be 20 feet. Calibration goals for the groundwater level residuals were set such that no more than 10 percent of the observed groundwater levels would exceed the acceptable residual level of 20 feet.
• 68.5% of observed groundwater levels are within +/- 10 feet of its respective simulated values • 96.2% of observed groundwater levels are within +/- 20 feet of its respective simulated values • 99.5% of observed groundwater levels are within +/- 30 feet of its respective simulated values The residual histogram and scatter plot of simulated versus observed values for the ESJ Subbasin original calibration wells for the calibration period is shown in Figure 14.

Figure 14: Calibration Statistics of Historical ESJWRM Version 3.0

3.4.3 Sensitivity Analysis
Sensitivity analysis is a way of investigating how sensitive certain model results are to changes in certain model parameters. A sensitive parameter is when the simulation results are greatly affected by changes in that parameter within its valid range. Conversely, an insensitive parameter means the changes in that parameter within its valid range do not affect the simulation results greatly.

Model parameters that are sensitive can be the largest sources of error and uncertainty when not precisely measured and well understood. Historical ESJWRM Version 2.0 sensitivity analysis revealed that none of the sensitivity runs resulted in a significant improvement in statistics or results. This means that the model was stable and that the calibration was at or near an optimal point when global parameter changes are considered.

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ESJWRM Version 3.0 October 2024
Since there was not significant changes to the model calibration between Historical ESJWRM Version 2.2 and Historical ESJWRM Version 3.0, updated sensitivity analysis was not performed at this time.

3.5 Historical Model Results
A water budget balances supplies, demands, and any subsequent change in storage occurring within the specific portion of the hydrologic cycle. IWFM automatically outputs budgets at the subregion scale for processes involving groundwater, land surface, streams, root zone, small watersheds, and unsaturated zone.

IWFM can output budgets down to a single element or any specific grouping of elements.

During this step of the calibration process, model results are reviewed and summarized into monthly and annual (by water year) budgets. The primary budgets reviewed for calibration are the land and water use budget and the groundwater budget. After extensive budget analysis, key model datasets and parameters are adjusted, particularly groundwater aquifer parameters, to better match local budgets from local agricultural water purveyors and local planning efforts. The Historical ESJWRM Version 3.0 water budget results are summarized in the following sections.

3.5.1 Land and Water Use Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual water demand for the Subbasin within the calibration period was 1,272 thousand acre-feet (TAF), consisting of 1,149 TAF agricultural demand and 123 TAF urban demand. This demand was met by an annual average of 568 TAF of surface water deliveries (512 TAF of agricultural and 56 TAF of urban deliveries) and was supplemented by 723 TAF of groundwater production (657 TAF of agricultural and 66 TAF of urban pumping). The average annual water surplus for the Subbasin within the calibration period was 18 TAF. Of this annual average, all of the surplus is from agricultural excess and the urban shortage is extremely minor at 1.4 TAF. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. The small agricultural surplus indicates a minor misalignment of demands and supplies likely due to the timing, volume, or delivery location of the supplies.

The annual simulated land and water use budgets for the calibration period are presented in Figure 15 and Figure 16 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands and water supplies. If supply and demand do not balance, there is a surplus or shortage indicated on the land and water use budget. Table 6 shows the annual averages described above for Historical ESJWRM Version 3.0’s calibration period.

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ESJWRM Version 3.0 October 2024
Table 6: ESJ Subbasin Land and Water Use Budget Annual Averages of Historical ESJWRM Version 3.0
Land and Water Use Budget Component
ESJWRM
Version 3.0
Annual
Average for
WY 1996-
2023
Agricultural Area (thousand acres) 387
Agricultural Demand (TAF) 1,149
Agricultural Groundwater Pumping (TAF) 657
Agricultural Surface Water Deliveries (TAF) 512
Agricultural Surplus (TAF)1 20
Urban Area (thousand acres) 69
Urban Demand (TAF) 123
Urban Groundwater Pumping (TAF) 66
Urban Surface Water Deliveries (TAF) 56
Urban Shortage (TAF)1 1
1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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ESJWRM Version 3.0 October 2024
Figure 15: ESJ Subbasin Agricultural Demand of Historical ESJWRM Version 3.0 Figure 16: ESJ Subbasin Urban Demand of Historical ESJWRM Version 3.0 ATTACHMENT 2
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ESJWRM Version 3.0 October 2024

3.5.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget, corresponding to the major hydrologic processes affecting groundwater flow in the ESJ Subbasin, are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) The largest component in the groundwater budget is an average annual 732 TAF of pumping, offset by 275 TAF of deep percolation, a net gain from stream of 159 TAF, 170 TAF of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a net boundary inflow of 79 TAF annually. The cumulative change in groundwater storage can be calculated from the change in groundwater storage. The groundwater storage in ESJ Subbasin during the calibration period was an average of -48 TAFY. These averages are shown in Table 7 and the Subbasin annual groundwater budget is shown in Figure 17.

Table 7 shows the annual averages described above for Historical ESJWRM Version 3.0’s calibration period. The average annual deficit in groundwater storage estimation determined using Historical ESJWRM Version 1.1 was 41 TAF (1996-2015) and in Historical ESJWRM Version 2.0 was 37 TAF (1996-2020). The average annual groundwater storage deficit in Historical ESJWRM Version 3.0 is estimated to be 48 TAF. This change in storage deficit is as a result of model updates, data refinements, period of record updates, and calibration updates.

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ESJWRM Version 3.0 October 2024
Table 7: ESJ Subbasin Hydrologic Groundwater Budget of Historical ESJWRM Version 3.0 Hydrologic Groundwater Budget Component
ESJWRM
Version 3.0
Annual
Average for
WY 1996-2023
Deep Percolation (TAF) 275
Deep Percolation of Precipitation (TAF) 60
Deep Percolation of Applied Water (TAF) 215
Other Recharge (TAF) 170
Net Stream Seepage (TAF)1 159
Net Boundary Inflow (TAF) 79
Groundwater Pumping (TAF) 732
Change in Groundwater Storage (TAF) -48
Figure 17: ESJ Subbasin Hydrologic Groundwater Budget of Historical ESJWRM Version 3.0 1 ESJGWA updates the ESJWRM approximately once per year as new data becomes available. Upon completion of the historical ESJWRM Version 3.0, comments regarding Calaveras River seepage were made that require further analysis and may require a recalibration of the model. This additional information on Calaveras River seepage will be considered during the next round of model updates.

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ESJWRM Version 3.0 October 2024
4 Projected Conditions Baseline Update
The refinements and enhancements made to the historical data for the updated historical calibration ESJWRM (Historical ESJWRM Version 3.0) required an update to the projected conditions baseline ESJWRM. The version of the Projected Conditions Baseline (PCBL) presented in the GSP finalized in November 2019 is called PCBL Version 1.0. The updated version of the PCBL using Historical ESJWRM Version 2.0 extended dataset and calibration results is referred to as PCBL Version 2.0. The updated version resulting from Historical ESJWRM Version 3.0 is PCBL Version 3.0. This section presents the key data sources and assumptions used to develop the PCBL Version 3.0 and provides the model results.

The PCBL used to develop the projected water budgets represents estimated long-term hydrologic conditions of the Subbasin under the foreseeable future level of development. The future level of development represents approximately water year 2040 or the closest information available from planning documents.

4.1 Assumptions Used to Develop Projected Conditions Baseline Update This section discusses the assumptions made in converting PCBL Version 2.0 to PCBL Version 3.0. The data and calibration parameters were updated to be consistent with the Historical ESJWRM Version 3.0. Initial groundwater levels and soil conditions in the PCBL represent those at the end of the simulation period of the Historical ESJWRM Version 3.0 (September 30, 2023).

Consistent with Section 354.18(c)(3) of the GSP Regulations, an analysis was performed for the Subbasin evaluating the projected water budget. Section 354.18(c)(3) of the GSP Regulations states:
“(3) Projected water budgets shall be used to estimate future baseline conditions of supply, demand, and aquifer response to Plan implementation, and to identify the uncertainties of these projected water budget components.”

4.1.1 Hydrology
The GSP version of PCBL Version 1.0 included 50 years of hydrology data from water years 1969 through 2018 (October 1968 through September 30, 2018) and was documented in the ESJ Subbasin GSP (ESJGWA, 2019).

The updated version PCBL Version 2.0 used 52 years of hydrology data from water years 1969 through 2020 (October 1968 through September 30, 2020) (Woodard & Curran, 2022a). PCBL Version 3.0 has 55 years of hydrology data from water years 1969 through 2023 (October 1968 through September 30, 2023). The projected 55 years of hydrology used in PCBL Version 3.0 meet the SGMA requirements to evaluate how the Subbasin’s surface and groundwater systems may react in the future under representative hydrologic conditions.

4.1.1.1 Precipitation and Hydrologic Water Year Types
Historical precipitation or rainfall in the ESJ Subbasin was used to identify the hydrologic period that would provide a representation of wet, dry, and extreme periods needed for PCBL Version 3.0. Figure 18 shows the Subbasin annual precipitation (blue columns), average precipitation (green line) of approximately 16 inches, and cumulative departure from mean precipitation (orange line) for each water year from 1969 through 2023.

This plot represents the spatially-averaged precipitation across ESJ Subbasin elements developed from PRISM precipitation data. The long-term average precipitation is subtracted from annual precipitation within each water year to develop the departure from average precipitation for each water year. Starting at the first year analyzed, the departures are added cumulatively for each subsequent year. Wet years have a positive departure and upward slopes, dry years have a negative departure and downward slopes, and a year with exactly average precipitation would have zero departure. More severe events are shown by steeper slopes and greater changes.

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ESJWRM Version 3.0 October 2024
Each year on the x-axis in Figure 18 is indicated with the San Joaquin Valley Water Year Hydrologic Classification Index published by DWR. The 55 years of the PCBL, from WY 1969 through 2023, represent a range of hydrologic conditions, as identified by the water year types in the San Joaquin Valley Water Year Hydrologic Classification, which classifies water years 1901 through 2023 as Wet (W), Above Normal (AN), Below Normal (BN), Dry (D), and Critical (C) based on inflows to major reservoirs or lakes. A description of how this index is calculated and the specific data used to calculate this index is available online from CDEC at http://cdec.water.ca.gov/cgi-progs/iodir/WSIHIST (DWR CDEC). In the 55 years of hydrology used in the PCBL Version 3.0, there are 16 Critical years, 9 Dry years, 4 Below Normal years, 7 Above Normal years, and 19 Wet years.

Figure 18: Historical Precipitation in ESJ Subbasin in PCBL Version 3.0 To facilitate assumptions for baseline water supplies and demands, the five San Joaquin Valley water year types were aggregated into three water year type groups. Critical and Dry years are combined into one category in the baseline water year types (called Dry years), Above Normal and Below Normal years are also combined into one category (Normal years), and Wet years remain in one category (called Wet years). With this breakdown, the three baseline water year types have a distribution of 25 Dry years, 11 Normal years, and 19 Wet years.

These baseline water year types (Table 8) are used in the remainder of the PCBL data development and results discussion.

As evident in Figure 18, there are four periods of extreme drought in which there are sequences of critical years where the cumulative departure from mean precipitation drops significantly in a steep slope. To capture future extreme dry year periods that may occur in the PCBL, the following 13 water years were designated as Drought periods: 1976-1977, 1987-1992, 2014-2015, and 2020-2022. Drought years are highlighted in red on the x-axis of Figure 18 and distinguished in Table 8.

An 11-year period (WY 2013-2023) of historical hydrology was selected to form the basis of projected data developed by averaging recent historical data. This period was selected because of the reliability of the ATTACHMENT 2
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historical data in Historical ESJWRM Version 3.0 during these years and because the distribution of water year types was relatively consistent with the overall PCBL hydrology. Precipitation data in the PCBL is reflective of historical actual precipitation. Precipitation will be modified under climate change scenarios, as described in Section 5.3.1 of this report.

Table 8: Baseline Hydrologic Water Year Types in PCBL Version 3.0 Baseline
Year
Water
Year
San Joaquin
Valley Water
Year Hydrologic
Classification
Baseline
Year
Type
Baseline
Year
Water
Year
San Joaquin
Valley Water
Year Hydrologic
Classification
Baseline
Year
Type
1 1969 Wet Wet 29 1997 Wet Wet
2 1970 Above Normal Normal 30 1998 Wet Wet
3 1971 Below Normal Normal 31 1999 Above Normal Normal
4 1972 Dry Dry 32 2000 Above Normal Normal
5 1973 Above Normal Normal 33 2001 Dry Dry
6 1974 Wet Wet 34 2002 Dry Dry
7 1975 Wet Wet 35 2003 Below Normal Normal
8 1976 Critical Drought 36 2004 Dry Dry
9 1977 Critical Drought 37 2005 Wet Wet
10 1978 Wet Wet 38 2006 Wet Wet
11 1979 Above Normal Normal 39 2007 Critical Dry
12 1980 Wet Wet 40 2008 Critical Dry
13 1981 Dry Dry 41 2009 Below Normal Normal
14 1982 Wet Wet 42 2010 Above Normal Normal
15 1983 Wet Wet 43 2011 Wet Wet
16 1984 Above Normal Normal 44 2012 Dry Dry
17 1985 Dry Dry 45 2013 Critical Dry
18 1986 Wet Wet 46 2014 Critical Drought
19 1987 Critical Drought 47 2015 Critical Drought
20 1988 Critical Drought 48 2016 Dry Dry
21 1989 Critical Drought 49 2017 Wet Wet
22 1990 Critical Drought 50 2018 Below Normal Normal
23 1991 Critical Drought 51 2019 Wet Wet
24 1992 Critical Drought 52 2020 Dry Drought
25 1993 Wet Wet 53 2021 Critical Drought
26 1994 Critical Dry 54 2022 Critical Drought
27 1995 Wet Wet 55 2023 Wet Wet
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Baseline
Year
Water
Year
San Joaquin
Valley Water
Year Hydrologic
Classification
Baseline
Year
Type
Baseline
Year
Water
Year
San Joaquin
Valley Water
Year Hydrologic
Classification
Baseline
Year
Type
28 1996 Wet Wet

4.1.1.2 Evapotranspiration
No changes to evapotranspiration in ESJ Subbasin were implemented in PCBL Version 3.0. Historical ESJWM Version 3.0 evapotranspiration by land use type and by model subregion is assumed to be consistent into the future. The evapotranspiration will be modified under climate change scenarios, as described in Section 5.3.1 of this report.

4.1.1.3 Streamflow
No change was assumed in PCBL Version 3.0 to all stream inflows. Stream inflows will be modified under climate change scenarios, as described in Section 5.3.1 of this report

4.1.2 Land Use and Cropping Patterns
PCBL Version 3.0 used the latest land use dataset available and incorporated urban buildout to reflect the 2040 land use conditions. Land use and cropping patterns are based on the most recent, comprehensive, and modelwide land use survey from DWR (DWR, 2022), with adjustments based on local information and input. This spatial land use data was mapped to ESJWRM model elements and is used as the basis of the PCBL as the latest source of reliable land use data covering the entire model domain. The same edits were made to elements representing LCSD and LCWD to convert agricultural land to urban development, as described above for Historical ESJWRM Version 3.0 discussed in Section 3.2.5 and shown in Figure 2.

To represent the extent of urban buildout in 2040, the urban areas in the 2022 land use dataset were expanded to either the sphere of influence or general plan boundaries and are held constant during the 55 years of the PCBL Version 3.0 simulation. The areas with urban buildout include Lodi, Stockton, Lathrop, Manteca, Ripon, and Escalon. No growth was assumed for the Jenny Lind urban area. While there is agricultural growth anticipated in the eastern areas of the Subbasin and potential conversion of existing agricultural land to permanent irrigated crops, no reliable projections were available to include in the simulation; therefore, no additional agricultural land growth was added to the PCBL. Thus, cropping acreage is reduced only where urban expansion occurs. This means that due to projected urban growth of over 48,000 acres, agricultural acreage is expected to decrease by approximately 32,000 acres and undeveloped acreage decreases by under 16,000 acres. Table 9 shows the differences between the DWR 2022 data and the ultimate baseline acreage once urban buildout was incorporated. Figure 19 is a pie chart of the PCBL Version 3.0 cropping pattern.

Table 9: ESJ Subbasin Land Use Acreages by Land Use Type in PCBL Version 3.0 Land Use Type DWR 2022
Survey (acres)
Baseline Model
(acres)
Change from
DWR 2022 Survey
(acres)
Ag Acreage 397,749 365,213 -32,536
Urban Acreage 80,712 128,966 48,255
Undeveloped
Acreage 274,874 259,155 -15,719
Riparian 11,356 11,356 0
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Figure 19: 2022 Grouped Crop Acreage for ESJ Subbasin in PCBL Version 3.0

4.1.3 Water Supply and Demand
Urban water demand in the PCBL Version 3.0 is generally reflective of 2040 conditions. Demand and supply projections were generally available for 2040 or 2045 conditions from urban water management plans (UWMPs). Water demand and supply assumptions are based on the 2020 UWMPs, other planning documents, and the most current information provided by purveyors. Urban demand and supply projections were estimated for three water year types for wet, normal, and dry conditions, with drought periods assumed of critical water supply. Projections for wet years were assumed to be the same as normal conditions when wet year projections were unavailable. After the projected surface water supply and demand were pulled from the planning documents, the projected municipal pumping was calculated as the difference between surface water supply and demand. For modeling purposes, supply was assumed to meet the demand with no surplus.

Agricultural water supply largely used the 11-year averages of grouped water year types from recent historical data (WY 2013-2023). All PCBL annual average surface water diversion volumes are included in Table 4.

In each of the drought period years in the PCBL, it was assumed that the surface water supply delivered was at the 2015 level of supply if lower than the dry year supply. Pumping was increased accordingly if not calculated within the model. In this way, the PCBL is based on the most recent critical year actual historical delivery data and simulates periods of extreme stress on the groundwater system.

4.2 Projected Conditions Baseline Results
This section provides a summary of the ESJWRM PCBL Version 3.0 results.

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4.2.1 Land and Water Use Water Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual projected water demand for the Subbasin within the 55-year simulation period is 1,309 thousand acre-feet (TAF), consisting of approximately 1,153 TAF estimated agricultural demand and 156 TAF estimated urban demand. This demand is met by an annual average of 525 TAF of surface water deliveries (452 TAF of agricultural and 73 TAF of urban deliveries) and is supplemented by 788 TAF of groundwater production (721 TAF of agricultural and 67 TAF of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 19 TAF of agricultural surplus and 16 TAF urban shortage in the Subbasin scale water use budget, which is less than significant relative to the total volume of water use. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

These annual averages are shown in Table 10. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 20 and Figure 21 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

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Table 10: ESJ Subbasin Land and Water Use Budget Annual Average of PCBL Version 3.0 Land and Water Use Budget Component
PCBL
Version 3.0
Annual
Average
Agricultural Area (thousand acres) 365
Agricultural Demand (TAF) 1,153
Agricultural Groundwater Pumping (TAF) 721
Agricultural Surface Water Deliveries (TAF) 452
Agricultural Surplus (TAF)1 19
Urban Area (thousand acres) 129
Urban Demand (TAF) 156
Urban Groundwater Pumping (TAF) 67
Urban Surface Water Deliveries (TAF) 73
Urban Shortage (TAF)1 16
Figure 20: ESJ Subbasin Projected Agricultural Demand of PCBL Version 3.0 1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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Figure 21: ESJ Subbasin Projected Urban Demand of PCBL Version 3.0

4.2.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

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degree of uncertainty. Given this uncertainty, the projected long-term average annual the groundwater storage deficit in ESJ Subbasin in the PCBL is 30 TAFY. These annual averages are shown in Table 11. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 22.

Table 11: ESJ Subbasin Hydrologic Groundwater Budget Annual Average of PCBL Version 3.0 Hydrologic Groundwater Budget Component
PCBL
Version 3.0
Annual
Average
Deep Percolation (TAF) 270
Deep Percolation of Precipitation (TAF) 55
Deep Percolation of Applied Water (TAF) 215
Other Recharge (TAF) 165
Net Stream Seepage (TAF)1 240
Net Boundary Inflow (TAF) 94
Groundwater Pumping (TAF) 799
Change in Groundwater Storage (TAF) -30
Figure 22: ESJ Subbasin Projected Hydrologic Groundwater Budget of PCBL Version 3.0 1 ESJGWA updates the ESJWRM approximately once per year as new data becomes available. Upon completion of the historical ESJWRM Version 3.0, comments regarding Calaveras River seepage were made that require further analysis and may require a recalibration of the model. This additional information on Calaveras River seepage will be considered during the next round of model updates and any edits may cause changes to PCBL Version 3.0.

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5 Projected Conditions Baseline Update with Climate Change With the update of the PCBL Version 3.0, the potential impact of climate change on the Subbasin in the future was also updated. The version of the Projected Conditions Baseline with Climate Change (PCBL-CC) presented in the GSP finalized in November 2019 is called PCBL-CC Version 1.0. The updated version of the PCBL-CC using PCBL Version 2.0 with hydrology perturbation factors was referred to as PCBL-CC Version 2.0. Now, PCBL Version 3.0 with historical perturbation factors is PCBL-CC Version 3.0. Largely, PCBL-CC Version 2.0 and Version 3.0 use the same perturbation factors, but PCBL-CC Version 3.0 extends the simulation time period by three years. This section presents the climate change methodology, data sources, and assumptions used to develop the PCBL-CC Version 3.0 and provides the model results.

In PCBL-CC Version 1.0, the ESJGWA decided to use 2070 Central Tendency perturbation factors as a reasonable estimation of the impact of climate change. PCBL-CC Version 3.0 also used 2070 Central Tendency climate change conditions. This decision may be re-evaluated if DWR updates its climate change methodology or if the Subbasin determines a need to plan for more extreme future scenarios.

5.1 Climate Change Background and Methods
SGMA requires taking into consideration uncertainties associated with climate change in the development of GSPs. Consistent with Section 354.18(d)(3) and Section 354.18(e) of the GSP Regulations, an analysis was performed for the Subbasin evaluating the projected water budget with and without climate change conditions.

Section 354.18(d)(3) of the GSP Regulations states:
“(d) The Agency shall utilize the following information provided, as available, by the Department pursuant to Section 353.2, or other data of comparable quality, to develop the water budget:
(1) Historical water budget information for mean annual temperature, mean annual precipitation, water year type, and land use.
(2) Current water budget information for temperature, water year type, evapotranspiration, and land use. (3) Projected water budget information for population, population growth, climate change [emphasis added], and sea level rise.”
Section 354.18(e) states:
“(e) Each Plan shall rely on the best available information and best available science to quantify the water budget for the basin in order to provide an understanding of historical and projected hydrology, water demand, water supply, land use, population, climate change [emphasis added], sea level rise, groundwater and surface water interaction, and subsurface groundwater flow. If a numerical groundwater and surface water model is not used to quantify and evaluate the projected water budget conditions and the potential impacts to beneficial uses and users of groundwater, the Plan shall identify and describe an equally effective method, tool, or analytical model to evaluate projected water budget conditions.”

5.1.1 DWR Guidance
Climate change analysis is an area of continued evolution in terms of methods, tools, forecasted datasets, and the predictions of greenhouse gas concentrations in the atmosphere. The approach developed for this GSP is based on the methodology in DWR’s guidance document (DWR, 2018a). The “best available information” related to climate change in the ESJ Subbasin was deemed to be the information provided by DWR combined with basin-specific modeling tools. The following resources from DWR were used in the climate change analysis:

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• SGMA Data Viewer
• Guidance for Climate Change Data Use During Sustainability Plan Development and Appendices (Guidance Document)
• Water Budget BMP
• Climate Change Desktop IWFM Tools
The SGMA Data Viewer contains climate change forecast datasets for download (DWR, 2018b). The guidance document details the approach, development, applications, and limitations of the datasets available from the SGMA Data Viewer (DWR, 2018b). The Water Budget BMP describes in greater detail how DWR recommends projected water budgets with climate change be estimated (DWR, 2016). The Desktop IWFM Tools are available to estimate the projected precipitation and evapotranspiration inputs under climate change conditions (DWR, 2018a).

The methods suggested by DWR in the above resources were used, with modifications where needed, to ensure the results would be reasonable for the Eastern San Joaquin Subbasin and align with the assumptions of the ESJWRM. Figure 23 shows the overall process developed for the Subbasin consistent with the Climate Change Resource Guide (DWR, 2018a) and describes workflow beginning with projected conditions inputs and assumptions to perturbed 2070 conditions for the projected conditions.

Figure 23: ESJWRM Climate Change Analysis Process for PCBL-CC Version 3.0 The process described in Figure 23 of developing a projected water budget with and without climate change was discussed with DWR staff before the 2020 GSP was created and is consistent with the regulations. Further, it enables the analysis to account for variability in demand and supply separate from the uncertainty associated with climate change forecasts. Table 12 summarizes the forecasted variable datasets provided by DWR that were used to carry out the climate change analysis (DWR, 2018a). The Variable Infiltration Capacity (VIC) model referred to in Table 12 is the fully mechanistic hydrologic model used by DWR to derive hydrographs under standard and climate change conditions.

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Table 12: DWR-Provided Datasets for PCBL-CC Version 3.0 Input Variable DWR-Provided Dataset
Unimpaired Streamflow
Combined VIC model runoff and baseflow to
generate change factors, provided by HUC 8
watershed geometry
Impaired Streamflow (Ongoing
Operations) CalSim II time series outputs
Precipitation VIC model-generated GIS grid with associated change factor time series for each cell
Reference ETo VIC model-generated GIS grid with associated change factor time series for each cell

5.1.2 Climate Change Methodology
Accepted methods for estimating climate change impacts on groundwater are based on the assessment of impacts on the individual water resource system elements that directly link to groundwater. These elements include precipitation, streamflow, evapotranspiration and, for coastal aquifers, sea level rise as a boundary condition. For the Subbasin, sea level rise was not included.

The method for perturbing the streamflow, precipitation, and evapotranspiration input files is described in the following sections. A future scenario of 2070 climate forecasts was evaluated in this analysis, consistent with DWR guidance. DWR combined 10 global climate models (GCMs) for two different representative climate pathways (RCPs) to generate the central tendency scenarios in the datasets used in this analysis. The “local analogs” method (LOCA) was used to downscale these 20 different climate projections to a scale usable for California (DWR, 2018a). The 2070 central tendency among these projections serves to assess impacts of climate change over the long-term planning and implementation period.

Model simulation results reported in the published GSP have been updated in this section using the updated PCBL Version 3.0 completed as part of the 2024 update of the historical and projected conditions model. This PCBL Version 3.0 has a 55-year simulation baseline period with hydrology through WY 2023 incorporated.

Updates to the PCBL are documented in Section 4. Model results from the updated PCBL-CC Version 3.0 are reported in Section 5.3.

5.2 Projected Conditions Baseline with Climate Change Hydrology This section provides a summary of the data sources, methodology, and summarized results of the updates to the hydrology under climate change conditions.

5.2.1 Streamflow under Climate Change
Hydrologic forecasts for streamflow under various climate change scenarios are available from DWR as either a flow-based timeseries or a series of perturbation factors applicable to local data. DWR simulates volumetric flow in most regional surface water bodies by utilizing the Water Resource Integrated Modeling System (WRIMS, formally named CalSim II). While river flows and surface water diversions in the Calaveras, San Joaquin, and Stanislaus Rivers are simulated in CalSim II, there are significant variations when compared to local historical data. Due to the uncertainty in reservoir operations, flows from CalSim II provided by the state are not used directly. Instead, relative perturbation factors were used to derive surface water inflows and diversions for use in ESJWRM.

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Local tributaries and smaller streams within ESJ Subbasin are not simulated in CalSim II and must be simulated using adjustment factors developed by DWR for unregulated stream systems. Dry Creek flows were perturbed using this method. The resolution of these perturbation factors is at the Hydrologic Unit Code 8 watershed scale. CalSim II model runs are not available for the Mokelumne River, according to Appendix B, Table B-2 of DWR’s Climate Change Document (DWR, 2018a). Therefore, Mokelumne River flows used the perturbation factor method for consistency with the methodology applied to smaller streams. Though Mokelumne River is regulated by Camanche Reservoir, the climate change methodology available at the time did not make it possible to treat the river as impaired; this assumption will be revisited in future updates to climate change factors and methodology. The remaining streams simulated in the ESJWRM utilize the IWFM small watershed package, whose climate change impacts are calculated internally dependent on both precipitation and evapotranspiration refinement. Table 13Table 13: ESJWRM Stream Inflows presents the impaired and unimpaired streams in the ESJWRM for the Subbasin.

Table 13: ESJWRM Stream Inflows in PCBL-CC Version 3.0
Modeled Stream Impaired Unimpaired
Within ESJ Subbasin
Dry Creek X
Mokelumne River X
Calaveras River X
San Joaquin River X
Stanislaus River X
Within Model Area, Outside ESJ Subbasin
Tuolumne River x
Cosumnes River x

5.2.1.1 Unimpaired Flows
Change factors for unimpaired streams (Dry Creek and Mokelumne River) were downloaded from SGMA Data Viewer and multiplied by the projected conditions input streamflow data to calculated perturbed flows. DWR change factors are available through 2011; however, the model hydrologic period runs from WY 1969-2023.

Flows for the remaining model years beyond 2011 were synthesized using the change factor from the most recent matching water year type in the available dataset. Water Year types are designated for each year based on the San Joaquin Valley Runoff WY year type index (DWR CDEC). DWR uses five designations ranging from driest to wettest conditions: Critical, Dry, Below Normal, Above Normal, and Wet. Table 14Table 14: San Joaquin Valley Water Year Type Designations below shows the year type designations used to synthesize the remaining years (2011-2023).

The PCBL-CC Version 1.0 reported in the GSP only used hydrology baseline years through 2018. In the updated PCBL-CC Version 2.0, WY 2019 and WY 2020 were incorporated. In PCBL-CC Version 3.0, WY 2021, 2022, and 2023 were incorporated and added to Table 14 below. The climate change perturbation was carried out for the additional years of simulation using methods consistent with how the rest of the synthesized years were calculated in the GSP for unimpaired streamflows.

As part of the update to the PCBL Version 2.0, South San Joaquin Irrigation District (SSJID) outflows were incorporated as a new stream inflow to the model. However because these are operationally dependent flows, they were not perturbed in this climate change scenario.

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Table 14: San Joaquin Valley Water Year Type Designations Water Year Year Type
2003 Below Normal
2004 Dry
2005 Wet
2006 Wet
2007 Critical
2008 Critical
2009 Below Normal
2010 Above Normal
2011 Wet
2012 Dry
2013 Critical
2014 Critical
2015 Critical
2016 Dry
2017 Wet
2018 Below Normal
2019 Wet
2020 Dry
2021 Critical
2022 Critical
2023 Wet
Figure 24 shows the perturbed time series against the projected conditions scenario time series for Dry Creek through the 55-year simulation period and Figure 25 presents the exceedance probability curve. Figure 26 and Figure 27 show the same perturbed time series and exceedance curves, but for Mokelumne River. The exceedance curves are provided because they more clearly show the differences between the projected conditions scenario and the with-climate-change scenario. Generally, flows under the climate change scenario are slightly higher.

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Figure 24: Dry Creek Hydrograph for PCBL-CC Version 3.0 Figure 25: Dry Creek Exceedance Curve for PCBL-CC Version 3.0 ATTACHMENT 2
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5.2.1.2 Impaired Flows
CalSim II-estimated flows for point locations on the Calaveras River, San Joaquin River, and Stanislaus River were downloaded from DWR. These points obtained from CalSim II include:
• Calaveras River: New Hogan Reservoir Outflow
• San Joaquin River: San Joaquin River at Vernalis
• Stanislaus River: New Melones Reservoir Outflow
These flows represent projected hydrology based on reservoir outflow, operational constraints, and diversions and deliveries of water for the State Water Project and the Central Valley Project. CalSim II data from WY 1969- 2003 were available. For the years 2003-2023, streamflow was synthesized based on flows from WY 1969-2003 and the DWR year type index shown in Table 14. For example, the total monthly streamflow for October 2003 was calculated as the average of the monthly streamflows from October 1966 and October 1971 because they are the same water year type.

CalSim II simulated flows were compared with flows generated using the DWR-provided unimpaired perturbation factors. Streamflows simulated in CalSim II and those derived using the unimpaired adjustment factors did not present similar trends, particularly in dry years, due to CalSim II’s simulation of reservoir operations. DWR-provided unimpaired change factors do not account for variations in the operation of the reservoirs that would result from climate change conditions. Therefore, CalSim II outputs were considered a more appropriate starting dataset for regulated streams given that downstream flow is driven by surface water demand rather than natural flow.

The team explored a hybrid approach to improve upon the discrepancy between flows produced using CalSim II and perturbation factors, while accounting for some change in reservoir operations. In this approach, change factors are generated from the difference between the simulated future climate change CalSim II scenario for 2070 climate conditions and a “without climate change” CalSim II run. This “without climate change” run is the CalSim II 1995 Historical Detrended simulation run. The generated change factors from these two runs were then used to perturb the regulated river inflows simulated in the ESJWRM projected conditions scenario. For the purposes of simplicity, this method is referred to throughout the rest of the document as CalSim II Generated Perturbation Factors (CGPF). The CGPF method presents limitations given that the resulting flows are not directly obtained from an operations model. The actual mass balance on the reservoirs is not tracked in the estimates of the flows and, instead, the method relies on CalSim II tracking storage and managing the reservoir based on the appropriate rule curves.

The climate change perturbation was carried out for the additional years of simulation using methods consistent with how the rest of the synthesized years were calculated in the GSP for impaired streamflows.

Figure 28 through Figure 33 provide a comparison of project baseline condition and the results of the CGPF method described above for each stream within the ESJ Subbasin, updated for the 55-year simulation. Figure 34 through Figure 37 show the same hydrographs for streams within the model area, but outside of the ESJ Subbasin. Exceedance curves are included for each of the CGPF flows against the project baseline flows.

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Figure 32: San Joaquin River Hydrograph for PCBL-CC Version 3.0 Figure 33: San Joaquin River Exceedance Curve for PCBL-CC Version 3.0 ATTACHMENT 2
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5.2.2 Precipitation and Evapotranspiration under Climate Change Projected precipitation and evapotranspiration (ETo) change factors were calculated using a climate period analysis based on historical precipitation and ETo from January 1915 to December 2011 (DWR, 2018a). DWR used a macroscale hydrologic model that solves the water balance of a watershed, called the VIC Model.

Change factors provided by DWR were calculated as a ratio of the value of a variable under a “future scenario” divided by a baseline. That baseline data is the 1995 Historical Temperature Detrended scenario downscaled from GCM climate data. The “future scenario” corresponds to VIC outputs of the simulation of future conditions using GCM forecasted hydroclimatic variables as inputs. These change factors are thus a simple perturbation factor that corresponds to the ratio of a future with climate change divided by the past without it. Change factors are available on a monthly time step and are spatially defined by the VIC model grid. Supplemental tables with the time series of perturbation factors are available from DWR for each grid cell. DWR has made accessible a Desktop GIS tool for both IWFM and MODFLOW to process these change factors (DWR, 2018b).

5.2.2.1 Applying Change Factors to Precipitation
DWR change factors were multiplied by historical precipitation to generate projected precipitation under the 2070 central tendency future scenario using the Desktop IWFM GIS tool (DWR, 2018b). The tool calculates an area weighted precipitation change factor for each model grid geometry. This model grid geometry was based on polygons generated around the PRISM nodes within the model region used to specify rainfall depths.

However, the DWR tool only includes change factors through 2011. The remaining years of the time series were synthesized according to historically comparable water years. The perturbation factor from the corresponding month of the comparable year was applied to the baseline of the missing years (2012-2023) to generate projected values. Months with no precipitation in the baseline were assumed to have a monthly precipitation of 1 mm under climate change to account for increased precipitation that cannot be calculated from a baseline of 0 mm for these synthesized years. The comparable years that were used can be found in Table 15. These comparable years were determined by comparing total San Joaquin Valley runoff, DWR year type index, and total annual Subbasin precipitation.

Table 15: Comparable Water Years (based on Precipitation) for PCBL-CC Version 3.0 Water Year Not
Available in DWR
Tool
Comparable Water
Year
2012 2001
2013 1991
2014 1987
2015 1977
2016 2002
2017 1983
2018 1983
2019 2016
2020 2013
2021 2014
2022 2013
2023 2017
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The resulting perturbed precipitation values and the baseline precipitation values for the representative historical period can be found in Figure 38. The exceedance plot for these two times series can be found in Figure 39, both updated for 55 years of projected conditions simulation. The absolute difference between the PCBL-CC Version 3.0 and the PCBL Version 3.0 are shown in Figure 40.

Figure 38: Perturbed Precipitation Under Climate Change for PCBL-CC Version 3.0 Figure 39: Perturbed Precipitation Exceedance Curve for PCBL-CC Version 3.0 ATTACHMENT 2
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Figure 40: Subbasin Precipitation Difference with Climate Change Conditions for PCBL-CC Version 3.0

5.2.2.2 Applying Change Factors to Evapotranspiration
Potential ETo in the Subbasin varies geographically and by land use. The tool provided by DWR to process ETo was not used because of the minimal spatial variation in ETo in the Subbasin. DWR provides change factors for ETo that vary spatially based on the VIC model grid as described above. Change factors for November 1, 1964 through December 1, 2011 were averaged. For the purposes of this analysis, a localized averaged change factor of 1.082 or 1.084 was used depending on the crop type and where in the Subbasin that crop can be found. All ETo in the Subbasin is expected to increase. However, almonds, pistachios, walnuts, cherries, pasture, corn, and rice ETo are expected to increase more with climate change in the South of the Subbasin in comparison to the North. All land uses in the South and the remaining crops in the North are perturbed with a single average change factor of 1.084.

This average ETo change factor was then applied to the historical ETo time series for each crop type. Because there is currently no interannual variability in ETo in ESJWRM, the same perturbed time series was applied across all simulation years. Refinement to the simulated evapotranspiration of almonds, walnuts, and cherries under 2070 climate conditions is shown in Figure 41 through Figure 43.

There were no changes made to the projected conditions simulation for evapotranspiration in the PCBL Version

3.0 model update. Additionally, as is currently set up in the model, there is no variation by year, only by month.

Therefore, there were no adjustments made to the evapotranspiration model input under the projected conditions with climate change scenario while extending the model through the 55 year simulation.

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Figure 41: Monthly Evapotranspiration Variability for Almonds for PCBL-CC Version 3.0 Figure 42: Monthly Evapotranspiration Variability for Walnuts for PCBL-CC Version 3.0 ATTACHMENT 2
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Figure 43: Monthly Evapotranspiration Variability for Cherries for PCBL-CC Version 3.0 Figure 44: Monthly Evapotranspiration Variability for Vineyards for PCBL-CC Version 3.0

5.3 Projected Conditions Baseline with Climate Change Results This section provides a summary of the ESJWRM PCBL-CC Version 3.0 results.

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5.3.1 Differences in Precipitation, Evapotranspiration, and Streamflow under Climate Change
Under the climate change scenario (PCBL-CC Version 3.0), the average annual precipitation is overall 10 percent higher than the projected conditions scenario (PCBL Version 3.0), increasing from 992,000 AFY to 1,087,000 AFY or from about 15.6 in/year to 17.0 in/year. Similarly, the average annual volume of evapotranspiration in PCBL-CC Version 3.0 is 6 percent higher than the PCBL Version 3.0, increasing from 1,302,000 AFY to 1,384,000 AFY . Despite there being higher flows in streams in PCBL-CC Version 3.0, the anticipated surface water diversions were not expected to change in PCBL-CC Version 3.0 due to both availability of water in the stream and water rights agreements limiting diversion months. With a similar surface water supply and increased water demands under the PCBL-CC Version 3.0, private groundwater production is simulated to increase by approximately 10 percent, from 799,000 AFY to 879,000 AFY. Under climate change conditions, due to increased groundwater use driven by higher agricultural demands, the depletion in aquifer storage is expected to increase by about 87 percent to an average annual storage change of -56,000 AFY in the PCBL-CC Version

3.0, from -30,000 AFY in the PCBL Version 3.0. A graphical representation of simulated changes to precipitation, evapotranspiration, and groundwater pumping are presented in Figure 45 though Figure 47. Full water budgets for the land surface and groundwater systems are discussed in Sections 5.3.2 and 5.3.3.

Figure 45: Simulated Changes in Precipitation due to Climate Change in PCBL-CC Version 3.0 Note: Negative indicates PCBL Version 3.0 value was larger and positive indicates PCBL-CC Version 3.0 was larger. The climate change scenario largely has more precipitation than the projected conditions scenario.

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Figure 46: Simulated Changes in Evapotranspiration due to Climate Change in PCBL-CC Version 3.0
Note: PCBL-CC Version 3.0 evapotranspiration is always larger than the PCBL Version 3.0 for all simulated years.

Figure 47: Simulated Changes in Groundwater Pumping due to Climate Change in PCBL-CC Version 3.0
Note: PCBL-CC Version 3.0 groundwater pumping is always larger than the PCBL Version 3.0 for all simulated years.

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5.3.2 Land and Water Use Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual PCBL-CC Version 3.0 demand for the Subbasin within the 55-year simulation period is 1,396 thousand acre-feet (TAF), consisting of approximately 1,240 TAF expected agricultural demand and 156 TAF expected urban demand. This demand is met by an annual average of 525 TAF of surface water deliveries (452 TAF of agricultural and 73 TAF of urban deliveries) and is supplemented by 868 TAF of groundwater production (801 TAF of agricultural and 67 TAF of urban pumping). Due to uncertainties in the estimation of PCBL-CC Version 3.0 agricultural demand and historical supply records, there is 14 TAF of agricultural surplus and 16 TAF of urban shortage in the Subbasin scale water use budget, which is insignificant relative to the total volume of water use. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus. These annual averages are shown in Table 16. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 48 and Figure 49 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

A comparison between the PCBL Version 3.0 and the PCBL-CC Version 3.0 is included in Table 17. As shown in Section 5.3.1 and Figure 46, evapotranspiration is higher in the PCBL-CC Version 3.0 compared to the PCBL Version 3.0 in every year of the simulation. This higher evapotranspiration translates to a higher agricultural demand in the PCBL-CC Version 3.0 of 86,100 AFY, which must be met by increased groundwater pumping of 80,300 AFY. The slight difference between the demand increase and the groundwater pumping increase is due to a decrease in 100 AFY of agricultural surface water deliveries. Small changes in surface water availability in streams occurred in the PCBL-CC Version 3.0 compared to the PCBL Version 3.0 due to the impact of perturbation factors on monthly stream flows. On the urban demand side, there were no differences built into the assumptions for climate change for urban entities, so there were no changes to the urban areas in the PCBL-CC Version 3.0 versus the PCBL Version 3.0.

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Table 16: ESJ Subbasin Land and Water Use Budget Annual Average for PCBL-CC Version 3.0 Land and Water Use Budget Component

PCBL-CC
Version 3.0
Annual
Average
Agricultural Area (thousand acres) 365
Agricultural Demand (TAF) 1,240
Agricultural Groundwater Pumping (TAF) 801
Agricultural Surface Water Deliveries (TAF) 452
Agricultural Surplus (TAF) 14
Urban Area (thousand acres) 129
Urban Demand (TAF) 156
Urban Groundwater Pumping (TAF) 67
Urban Surface Water Deliveries (TAF) 73
Urban Shortage (TAF) 16
Table 17: ESJ Subbasin Land and Water Use Budget Annual Average Comparison Between the PCBL Version 3.0 and the PCBL-CC Version 3.0
Annual Average
Land and Water Use Budget
Component PCBL Version 3.0 PCBL-CCVersion 3.0
Climate Change
Impact (PCBL-CC
Version 3.0 minus
PCBL Version 3.0)
Agricultural Area (thousand acres) 365 365 0
Agricultural Demand (TAF) 1,153 1,240 86
Agricultural Groundwater Pumping (TAF) 721 801 80
Agricultural Surface Water Deliveries (TAF) 452 452 0
Agricultural Surplus (TAF) 19 14 -5
Urban Area (thousand acres) 129 129 0
Urban Demand (TAF) 156 156 0
Urban Groundwater Pumping (TAF) 67 67 0
Urban Surface Water Deliveries (TAF) 73 73 0
Urban Shortage (TAF) 16 16 0
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Figure 48: ESJ Subbasin Projected Agricultural Demand in the PCBL-CC Version 3.0 Figure 49: ESJ Subbasin Projected Urban Demand in the PCBL-CC Version 3.0 ATTACHMENT 2
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5.3.3 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

Corresponding to the major hydrologic processes affecting groundwater flow in the Subbasin, these are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) Pumping in the PCBL-CC Version 3.0 remains the largest component in the groundwater budget with an annual average 879 TAF. The PCBL-CC Version 3.0 offsets this pumping with 268 TAF of deep percolation, a net gain from stream of 276 TAF, 168 TAF of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a total subsurface inflow of 111 TAF annually. Due to inherent uncertainties in model input data, calculations, and calibration, all budget components have a degree of uncertainty. Given this uncertainty, the projected long-term average annual the groundwater storage deficit in ESJ Subbasin in the PCBL-CC Version 3.0 is 56 TAFY. These annual averages are shown in Table 18. The groundwater budget, with cumulative change in storage, is shown for the ESJ Subbasin in Figure 50.

A comparison of the PCBL Version 3.0 and the PCBL-CC Version 3.0 is shown in Table 19. The increase in groundwater pumping of 80,300 AFY is due to the increase in evapotranspiration and therefore increased agricultural demand as discussed above in Section 5.3.2 and Table 17. Additionally, increased precipitation in most years as shown in Figure 45 and discussed in Section 5.3.1, leads to overall increased deep percolation from precipitation and other recharge (specifically the ungauged watershed drainage component). The increased groundwater pumping causes groundwater levels to be lower, which then causes increased stream seepage, boundary inflow, and change in groundwater storage. The streamflow is overall higher in the PCBLCC Version 3.0, which may also allow for more stream seepage into the groundwater system.

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Table 18: ESJ Subbasin Hydrologic Groundwater Budget Annual Average in PCBL-CC Version

3.0 Hydrologic Groundwater Budget
Component
PCBL-CC Annual
Average
Deep Percolation (TAF) 268
Deep Percolation of Precipitation (TAF) 52
Deep Percolation of Applied Water (TAF) 216
Other Recharge (TAF) 168
Net Stream Seepage (TAF)1 276
Net Boundary Inflow (TAF) 111
Groundwater Pumping (TAF) 879
Change in Groundwater Storage (TAF) -56
Table 19: ESJ Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL Version 3.0 and the PCBL-CC Version 3.0 Annual Average
Hydrologic Groundwater Budget
Component PCBL Version 3.0 PCBL-CCVersion 3.0
Climate Change
Impact (PCBL-CC
Version 3.0 minus
PCBL Version 3.0)
Deep Percolation (TAF) 270 268 -2
Deep Percolation of Precipitation (TAF) 55 52 -3
Deep Percolation of Applied Water (TAF) 215 216 1
Other Recharge (TAF) 165 168 3
Net Stream Seepage (TAF)1 240 276 36
Net Boundary Inflow (TAF) 94 111 17
Groundwater Pumping (TAF) 799 879 80
Change in Groundwater Storage (TAF) -30 -56 -26
1 ESJGWA updates the ESJWRM approximately once per year as new data becomes available. Upon completion of the historical ESJWRM Version 3.0, comments regarding Calaveras River seepage were made that require further analysis and may require a recalibration of the model. This additional information on Calaveras River seepage will be considered during the next round of model updates and any edits may cause changes to PCBL-CC Version 3.0.

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Figure 50: ESJ Subbasin Projected Hydrologic Groundwater Budget in PCBL-CC Version 3.0 ATTACHMENT 2
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6 Projected Conditions Baseline Scenarios with Demand Reduction The goal of this section is to document the sustainable yield analysis in the ESJWRM, the methodologies used in the model development, and results of the demand reduction scenario model runs.

The sustainability goal description for the Subbasin is to maintain groundwater for the beneficial use of the people of the Subbasin by operating the Subbasin within its sustainable yield or by modification of existing management to address future conditions. This section focuses on the former option, which is to calculate the sustainable yield for the Subbasin to achieve the goal of generating a long-term (55-year) change in Subbasin groundwater storage of zero, a conservative approach, as a change in storage of greater than zero could occur without causing undesirable results. The latter option of modification of existing is discussed in the following section (Section 0).

The demand reduction actions, focusing on reduced groundwater production for simulation purposes to calculate the Subbasin sustainable yield, are added to the two existing model runs: PCBL Version 3.0 and PCBLCC Version 3.0. This section is adapted from what was originally developed as a technical memorandum attached to the 2022 Revised GSP (Woodard & Curran, 2022c).

6.1 Assumptions Used to Develop Projected Conditions Baseline Scenarios with Demand Reduction
The versions of the model with demand reduction are the Projected Condition BaseLine with Demand Reduction (PCBL-DR) and Projected Condition BaseLine with Climate Change and Demand Reduction (PCBLCC-DR). These two model runs were developed based on the original projected conditions baseline scenario with demand reduction in the 2019 GSP (PCBL-DR Version 1.0), which estimated future conditions of reduced supply, reduced demand, and the resulting aquifer response to implementation of sustainable conditions in the Subbasin, in order to bring the long-term (50-year) average change in groundwater storage to close to zero (ESJGWA, 2019). The same methodologies and similar demand reduction estimations were used in the development of the PCBL-DR Version 3.0 and the PCBL-CC-DR Version 3.0 to achieve the goal of generating a long-term (55-year) change in Subbasin groundwater storage that is close to zero.

There are uncertainties associated with projections scenarios of the ESJWRM due to the sequence of the hydrologic period, population projection, future cropping patterns, and irrigation practices and technologies, as well as uncertainties inherent in the representation of the groundwater and surface water system by the model. Therefore, to account for these uncertainties, a range of assumptions are used in running model scenarios to estimate the sustainable yield and an initial estimate of the demand reduction that may be required to achieve the sustainable yield over the 55-year planning period. Assumptions used in the PCBL-DR Version 3.0 and the PCBL-CC-DR Version 3.0 are discussed in detail in the following sections.

6.1.1 Projected Conditions Baseline with Demand Reduction The PCBL-DR Version 3.0 was developed based on the PCBL Version 3.0 with simulated reduction in urban and agricultural demand.

Urban Demand Reduction
Urban demand decreases by percentage across all major urban agencies in the Subbasin, including:
• City of Escalon
• City of Lathrop
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• City of Lodi
• City of Manteca
• City of Ripon
• City of Stockton
• Cal Water
• San Joaquin County in Stockton
PCBL-DR Version 1.0 assumed the urban groundwater pumping was cutback by 10%. The PCBL-DR Version 3.0 increased the assumption to a 15% reduction in urban demand. This was achieved in the model by reducing the per capita water use for the agencies above by 15% (i.e., setting them to 85% of the demand in the PCBL).

Agricultural Demand Reduction
In order to achieve a reduction in agricultural demand in the ESJWRM-DR, agricultural acreage is reduced by converting a portion of irrigated land to native vegetation. The agricultural demand decreases by percentage is based on the agricultural groundwater pumping by element and limited to elements at least 1 mile from major streams crossing the Subbasin. Figure 51 shows the model elements not within the 1-mile buffer of the major streams in the Subbasin. The reduction is applied only in the core area of the Subbasin (e.g., not to Cosumnes or Modesto Subbasins) and to the elements outside of the 1-mile buffer from the major streams.

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Figure 51: ESJWRM Elements in ESJ Subbasin not Within 1-Mile Buffer of the Major Streams for PCBL-DR and PCBL-CC-DR
The agricultural groundwater pumping reduction percentage applied to agricultural land is assumed based on the agricultural pumping density of each element in the Subbasin. The pumping reduction percentage is higher for the elements with higher agricultural pumping density. Under the PCBL-DR Version 3.0, if the agricultural groundwater pumping density is less than or equal to 2 acre-feet/acre (AF/acre), the pumping reduction percentage is assumed to be 0%; if the agricultural groundwater pumping density is greater 2 AF/acre and less than 3 AF/acre, the pumping reduction percentage is assumed to be 15%; if the agricultural groundwater pumping density is equal to or greater than 3 AF/acre, the pumping reduction percentage is assumed to be

27.5%, in order to achieve an average change in groundwater storage of zero over the 55-year planning period.

The comparison of the agricultural groundwater pumping percent reduction between the GSP scenario (PCBLDR Version 1.0) and the PCBL-DR Version 3.0 is shown in Table 20. Since the storage deficit of the PCBL Version

3.0 is slightly higher than it was in the PCBL Version 1.0, the agricultural demand reduction is more in the PCBLDR Version 3.0.

Figure 52 and Figure 53 show the agricultural groundwater pumping density for the PCBL Version 3.0 and the PCBL-DR Version 3.0, respectively. Compared to the PCBL Version 3.0, the agricultural groundwater pumping ATTACHMENT 2
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density in the PCBL-DR Version 3.0 is reduced in the elements with pumping density greater than 2 AF/acre and at least 1 mile from major streams in the Subbasin.

Table 20: Agricultural Groundwater Pumping Percent Reduction Comparison Between the GSP Scenario (PCBL-DR Version 1.0) and PCBL-DR Version 3.0 Percent Reduction PCBL-DR Version 1.0 PCBL-DR Version 3.0 Ag GW Pumping <=2
AF/acre 0% 0%
Ag GW Pumping 2-3
AF/acre 15% 15%
Ag GW Pumping >=3
AF/acre 25% 27.5%
Urban Demand 10% 15%
Figure 52: Agricultural Groundwater Pumping Density for PCBL Version 3.0 ATTACHMENT 2
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Figure 53: Agricultural Groundwater Pumping Density for PCBL-DR Version 3.0

6.1.2 Projected Conditions Baseline with Climate Change and Demand Reduction The PCBL-CC-DR Version 3.0 was developed based on the PCBL-CC Version 3.0 with simulated reduction in urban and agricultural demand.

Urban Demand Reduction
Urban demand decreases by percentage across all major urban agencies in the Subbasin, including:
• City of Escalon
• City of Lathrop
• City of Lodi
• City of Manteca
• City of Ripon
• City of Stockton
• Cal Water
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• San Joaquin County in Stockton
There was no PCBL-CC-DR Version 1.0 scenario, but the PCBL-CC-DR Version 2.0 scenario had an urban demand reduction of 10%. The PCBL-CC-DR Version 3.0 increased the assumption to a 15% reduction in urban demand. This was achieved in the model by reducing the per capita water use for the agencies above by 15% (i.e., setting them to 85% of the demand in the PCBL-CC).

Agricultural Demand Reduction
In order to achieve a reduction in agricultural demand in the ESJWRM-CC-DR, agricultural acreage is reduced by converting a portion of irrigated land to native vegetation The agricultural demand decreased by percentage using the same methodology as the PCBL-DR Version 3.0, and is based on the agricultural groundwater pumping by element and limited to elements at least 1 mile from the major streams crossing the Subbasin.

The reduction is again applied only to the core area of the Subbasin and to elements outside of the 1-mile buffer from the major streams, as shown in Figure 51.

Under the PCBL-CC-DR Version 3.0, if the agricultural groundwater pumping density is less than or equal to 2 acre-feet/acre (AF/acre), the pumping reduction percentage is assumed to be 0%; if the agricultural groundwater pumping density is greater 2 AF/acre and less than 3 AF/acre, the pumping reduction percentage is assumed to be 25%; if the agricultural groundwater pumping density is equal to or greater than 3 AF/acre, the pumping reduction percentage is assumed to be 37.5% to achieve an average change in storage of zero over the 55-year planning period. Since there was no PCBL-CC-DR Version 1.0 scenario in the original GSP, the comparison of the agricultural groundwater pumping percent reduction is between PCBL-CC-DR Version 2.0 and the PCBL-CC-DR Version 3.0. This is presented in Table 21. Since the storage deficit of the PCBL-CC Version

3.0 is higher than it was in the PCBL-CC Version 2.0, the agricultural demand reductions (i.e., percent decrease of agricultural land) are greater in the PCBL-CC-DR Version 3.0.

Figure 54 and Figure 55 show the agricultural groundwater pumping density for the PCBL-CC Version 3.0 and the PCBL-CC-DR Version 3.0, respectively. Compared to the PCBL-CC Version 3.0, the agricultural groundwater pumping density in the PCBL-CC-DR Version 3.0 is reduced in the elements with pumping density greater than 2 AF/acre and at least 1 mile from major streams in the Subbasin.

Table 21: Agricultural Groundwater Pumping Percent Reduction Comparison Between the PCBL-CC-DR Version 2.0 and PCBL-CC-DR Version 3.0
Percent Reduction PCBL-CC-DR
Version 2.0

PCBL-CC-DR
Version 3.0
Ag GW Pumping <=2
AF/acre 0% 0%
Ag GW Pumping 2-3
AF/acre 20% 25%
Ag GW Pumping >=3
AF/acre 30% 37.5%
Urban Demand 10% 15%
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Figure 54: Agricultural Groundwater Pumping Density for PCBL-CC Version 3.0 ATTACHMENT 2
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Figure 55: Agricultural Groundwater Pumping Density for PCBL-CC-DR Version 3.0

6.2 Projected Conditions Baseline Scenarios with Demand Reduction Results This section provides a summary of the ESJ Subbasin ESJWRM PCBL-DR Version 3.0 PCBL-CC-DR Version 3.0 model results. Both models share the same input files, except for the files related to climate change (stream inflows, evapotranspiration, and precipitation) and the files related to agricultural demand reduction.

Agricultural demand reduction is simulated by reducing non-ponded and ponded crop areas files and the files are different in the two models due to differences in the agricultural groundwater pumping reduction percentages calculated from the agricultural pumping density in the PCBL Version 3.0 compared to the PCBLCC Version 3.0. The area taken out of the non-ponded and ponded crop areas are added to the native vegetation areas in the two models. The files relating to the urban demand reduction simulated as per capita water use data are identical between the two models because the percent reduction is identical for urban areas between PCBL-DR Version 3.0 and PCBL-CC-DR Version 3.0.

6.2.1 Projected Conditions Baseline with Demand Reduction The section below summarizes the results for the PCBL-DR Version 3.0 as compared to the PCBL Version 3.0.

Neither of these runs include climate change.

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6.2.1.1 Land and Water Use Water Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual PCBL-DR Version 3.0 water demand for the Subbasin within the 55-year simulation period is 1,199 thousand acre-feet per year (TAFY), consisting of approximately 1,059 TAFY of agricultural demand and 140 TAFY of urban demand. This demand is met by an annual average of 526 TAFY of surface water deliveries (452 TAFY of agricultural and 73 TAFY of urban deliveries) and is supplemented by 693 TAFY of groundwater production (628 TAFY of agricultural and 65 TAFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 21 TAFY of surplus in the Subbasin-scale agricultural water supply, which is insignificant relative to the total volume of water use.

Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus. These annual averages are shown in Table 22. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 56 and Figure 57 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

Table 22 also includes the PCBL Version 3.0 results and a demand reduction benefit calculated as the PCBL-DR Version 3.0 results minus the PCBL Version 3.0 results. For urban areas, the 15% reduction in urban demand that was applied to the PCBL-DR Version 3.0 across all major agencies in the Subbasin is reflected in the reduction in urban demand of 16 TAFY compared to the PCBL Version 3.0. For agricultural areas, the PCBL-DR Version 3.0 has 26 thousand acres less of agricultural area, which results in 95 TAFY reduction in agricultural demand compared the PCBL Version 3.0. This represents a comparable reduction in agricultural groundwater pumping of 93 TAFY.

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Table 22: ESJ Subbasin Land and Water Use Budget Annual Average Comparison Between PCBL Version 3.0 and PCBL-DR Version 3.0
Land and Water Use Budget Component
Annual Average
PCBL Version

3.0 PCBL-DR
Version 3.0
DR Benefit
(PCBL-DR
Version 3.0
minus PCBL
Version 3.0)
Agricultural Area (thousand acres) 365 340 -26
Agricultural Demand (TAF) 1,153 1,059 -95
Agricultural Groundwater Pumping (TAF) 721 628 -93
Agricultural Surface Water Deliveries (TAF) 452 452 0
Agricultural Surplus (TAF)1 19 21 2
Urban Area (thousand acres) 129 129 0
Urban Demand (TAF) 156 140 -16
Urban Groundwater Pumping (TAF) 67 64 -3
Urban Surface Water Deliveries (TAF) 73 73 0
Urban Shortage (TAF)
1 16 2 -14
1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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Figure 56: ESJ Subbasin Projected Agricultural Demand in PCBL-DR Version 3.0 Figure 57: ESJ Subbasin Projected Urban Demand in PCBL-DR Version 3.0 ATTACHMENT 2
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6.2.1.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

Corresponding to the major hydrologic processes affecting groundwater flow in the Subbasin, these are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) Pumping in the PCBL-DR Version 3.0 remains the largest component in the groundwater budget with an annual average 704 TAFY. The PCBL-DR Version 3.0 offsets this pumping with 247 TAFY of deep percolation, a net gain from stream of 211 TAFY, 165 TAFY of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a total subsurface inflow of 81 TAFY. The cumulative change in groundwater storage can be calculated from the average annual change in groundwater storage. Due to inherent uncertainties in model input data, calculations, and calibration, all budget components have a degree of uncertainty. Given this uncertainty, the projected long-term average annual the groundwater storage deficit in ESJ Subbasin in the PCBL-DR Version 3.0 is -200 AFY, with the negative sign actually indicating an absence of groundwater overdraft and an increase in storage over the 55 years of the PCBL-DR Version 3.0. These annual averages are shown in Table 23. The groundwater budget, with cumulative change in storage, is shown for the ESJ Subbasin in Figure 58.

Table 23 also includes the PCBL Version 3.0 results and a demand reduction benefit calculated as PCBL-DR Version 3.0 results minus the PCBL Version 3.0 results. The results indicate that the demand reduction will resolve the PCBL Version 3.0 Subbasin overdraft condition when impacts due to climate change are not included. Without the demand reduction, the modeling shows an average overdraft of 30 TAFY over the 55 years of the PCBL Version 3.0 simulation. With the demand reduction in place, the modeling shows a projected overdraft of -200 AFY on average in the PCBL-DR Version 3.0. The PCBL-DR Version 3.0 shows an average increase of 30,200 AFY of groundwater in storage when compared to the PCBL.

Compared to PCBL Version 3.0, the PCBL-DR Version 3.0 has 95 TAFY less groundwater pumping due to the percentage reduction in urban per capita water use and agricultural areas, and 29 TAFY less stream seepage into the groundwater system due to higher groundwater levels. Other hydrologic groundwater budget component differences are small between the PCBL Version 3.0 and PCBL-DR Version 3.0.

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Table 23: ESJ Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between PCBL Version 3.0 and PCBL-DR Version 3.0
Hydrologic Groundwater Budget
Component
Annual Average
PCBL
Version

3.0 PCBL-DR
Version 3.0
DR Benefit
(PCBL-DR
Version 3.0
minus PCBL
Version 3.0)
Deep Percolation (TAF) 270 247 -23
Deep Percolation of Precipitation (TAF) 55 54 -1
Deep Percolation of Applied Water (TAF) 215 193 -22
Other Recharge (TAF) 165 165 0
Net Stream Seepage (TAF) 240 211 -29
Net Boundary Inflow (TAF) 94 81 -13
Groundwater Pumping (TAF) 799 704 -95
Change in Groundwater Storage (TAF) -30 0 30
Figure 58: ESJ Subbasin Projected Hydrologic Groundwater Budget in PCBL-DR Version 3.0 ATTACHMENT 2
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6.2.2 Projected Conditions Baseline with Climate Change and Demand Reduction The section below summarizes the results for the PCBL-CC-DR Version 3.0 as compared to the PCBL-CC Version

3.0. 6.2.2.1 Land and Water Use Water Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual PCBL-CC-DR Version 3.0 water demand for the Subbasin within the 55-year simulation period is 1,214 TAFY, consisting of approximately 1,074 TAFY of agricultural demand and 140 TAFY of urban demand. This demand is met by an annual average of 526 TAFY of surface water deliveries (453 TAFY of agricultural and 73 TAFY of urban deliveries) and is supplemented by 702 TAFY of groundwater production (637 TAFY of agricultural and 65 TAFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is about 16 TAFY of surplus in the Subbasin scale agricultural water use budget, which is insignificant relative to the total volume of water use. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus. These annual averages are shown in Table 24. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 59 and Figure 60 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

Table 24 also includes the PCBL-CC Version 3.0 results and a demand reduction benefit calculated as PCBL-CCDR Version 3.0 results minus PCBL-CC Version 3.0 results. For urban areas, the 15% reduction in urban demand that applied to the PCBL-CC-DR Version 3.0 across all major agencies in the Subbasin is reflected in the reduction in urban demand of 17 TAFY compared to the PCBL-CC Version 3.0. For agricultural areas, the PCBLCC-DR Version 3.0 has 44 thousand acres less agricultural area, which results in 166 TAFY less agricultural demand compared the PCBL-CC. This represents a comparable reduction in agricultural groundwater pumping of 164 TAFY.

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Table 24: ESJ Subbasin Land and Water Use Budget Annual Average Comparison Between PCBL-CC Version 3.0 and PCBL-CC-DR Version 3.0
Land and Water Use Budget
Component
Annual Average

PCBL-CC
Version 3.0

PCBL-CC-DR
Version 3.0
DR Benefit
(PCBL-CC-DR
Version 3.0
minus PCBLCC Version

3.0)
Agricultural Area (thousand acres) 365 321 -44
Agricultural Demand (TAF) 1,240 1,074 -166
Agricultural Groundwater Pumping (TAF) 801 637 -164
Agricultural Surface Water Deliveries
(TAF) 452 453 1
Agricultural Surplus (TAF)1 14 16 2
Urban Area (thousand acres) 129 129 0
Urban Demand (TAF) 156 140 -16
Urban Groundwater Pumping (TAF) 67 65 -3
Urban Surface Water Deliveries (TAF) 73 73 0
Urban Shortage (TAF)1 16 2 -14
1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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Figure 59: ESJ Subbasin Projected Agricultural Demand in the PCBL-CC-DR Version 3.0 Figure 60: ESJ Subbasin Projected Urban Demand in the PCBL-CC-DR Version 3.0 ATTACHMENT 2
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6.2.2.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

Corresponding to the major hydrologic processes affecting groundwater flow in the Subbasin, these are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) Pumping in the PCBL-CC-DR Version 3.0 remains the largest component in the groundwater budget with an annual average 713,200 AFY. The PCBL-CC-DR Version 3.0 offsets this pumping with 233,600 AFY of deep percolation, a net gain from stream of 223,200, 167,700 AFY of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a total subsurface inflow of 88,600 AFY annually. The cumulative change in groundwater storage can be calculated from the annual change in groundwater storage. Due to inherent uncertainties in model input data, calculations, and calibration, all budget components have a degree of uncertainty. Even with this uncertainty, the projected long-term average annual groundwater storage deficit in ESJ Subbasin in the PCBL-CC-DR Version 3.0 is 0 AFY. These annual averages are shown in Table 25. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 61.

Table 25 also includes the PCBL-CC results and a demand reduction benefit calculated as the PCBL-CC-DR Version 3.0 results minus the PCBL-CC results. The results indicate that the demand reduction will resolve the PCBL-CC Subbasin overdraft condition when impacts due to climate change are included. Without the demand reduction, the modeling shows an average overdraft of 56,200 AFY over the 55 years of the PCBL-CC simulation.

With the demand reduction in place, the modelling shows a projected overdraft of 0 AFY on average in the PCBL-CC-DR Version 3.0. The PCBL-CC-DR Version 3.0 shows an average increase of 56,200 AFY of groundwater in storage when compared to the PCBL-CC.

Compared to the PCBL-CC, with the demand reduction modeled, the PCBL-CC-DR Version 3.0 has 166,200 AFY less groundwater pumping due to the percentage reduction in urban per capita water use and agricultural areas, and 53,000 AFY less stream seepage into the groundwater system due to higher groundwater levels.

Other hydrologic groundwater budget component differences are small between the PCBL-CC and PCBL-CCDR Version 3.0 simulations.

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Table 25: ESJ Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL-CC and the PCBL-CC-DR Version 3.0
Hydrologic Groundwater Budget
Component
Annual Average

PCBL-CC PCBL-CC-DR
Version 3.0
DR Benefit
(PCBL-CC-DR
Version 3.0
minus PCBLCC)
Deep Percolation (TAF) 268 234 -34
Deep Percolation of Precipitation (TAF) 52 52 0
Deep Percolation of Applied Water (TAF) 216 182 -34
Other Recharge (TAF) 168 168 0
Net Stream Seepage (TAF) 276 223 -53
Net Boundary Inflow (TAF) 111 89 -22
Groundwater Pumping (TAF) 879 713 -166
Change in Groundwater Storage (TAF) -56 0 56
Figure 61: ESJ Subbasin Projected Hydrologic Groundwater Budget in the PCBL-CC-DR Version 3.0
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6.3 Projected Conditions Baseline Scenarios with Demand Reduction Groundwater Level Hydrographs
In order to evaluate how the chronic lowering of groundwater levels sustainability indicator might be impacted by Subbasin projected conditions, including climate change and demand reduction, groundwater hydrographs were analyzed for the 21 representative monitoring network wells selected in the GSP to monitor Subbasin groundwater levels. The goal of this analysis was to see where, when, and how often these groundwater hydrographs exceeded the minimum thresholds (MTs) established in the GSP. An undesirable result for groundwater levels as established in the GSP and refined in 2022 edits is when at least 25 percent of representative monitoring network wells (5 out of 21 wells) for the Subbasin are projected to exceed established MTs for two consecutive years. Figure 62 shows the location of the 21 representative monitoring network wells identified in the GSP as the monitoring network for the chronic lowering of groundwater levels.

Figure 62: ESJ Subbasin Groundwater Level Representative Monitoring Well Locations Groundwater level hydrographs at the 21 representative monitoring network wells were used to evaluate the impacts of the demand reductions under the PCBL-DR Version 3.0 and PCBL-CC-DR Version 3.0 as compared to the PCBL Version 3.0 and PCBL-CC Version 3.0, respectively. Two representative monitoring network wells ATTACHMENT 2
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(Well Swenson-3 and Well 01S10E04C001) reported groundwater levels below their MTs for at least one month in any of the models evaluated (PCBL Version 3.0, PCBL-DR Version 3.0, PCBL-CC Version 3.0, and PCBL-CC-DR Version 3.0). The hydrographs of these two representative monitoring network wells are shown and discussed in Sections 6.3.1 and 6.3.2. Subbasin undesirable results for groundwater levels are discussed in Section 6.3.3.

6.3.1 Projected Conditions Baseline without and with Demand Reduction Figure 63 shows the location of the representative monitoring network well (Well 01S10E04C001) with groundwater levels below its MT at any point in the 55-year projection of the PCBL Version 3.0 (without climate change or demand reduction). Figure 64 shows the locations of the same representative monitoring network wells with groundwater levels below their MTs in the PCBL without climate change but with demand reductions (PCBL-DR Version 3.0).

Figure 65 shows the hydrograph of Well 01S10E04C001. The hydrographs have horizontal lines representing the representative monitoring network well’s minimum threshold (red) and measurable objective (green). The ESJWRM model results are shown for the PCBL Version 3.0 (solid blue line), PCBL-DR Version 3.0 (dashed blue line), PCBL-CC Version 3.0 (solid brown line), PCBL-CC-DR Version 3.0 (dashed brown line). Any point these lines cross the red minimum threshold line represents an exceedance in at least one month of the simulation. The hydrographs are discussed in further detail after the figures.

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Figure 63: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in PCBL Version 3.0
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Figure 64: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in PCBL-DR Version 3.0
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Figure 65: Groundwater Level Hydrograph for Well 01S10E04C001 Under the PCBL Version 3.0 (without climate change or demand reduction), the representative monitoring network well with its hydrograph shown above in Figure 65 (Well 01S10E04C001) exceeded its MT. The text below discusses when and how often MT exceedances occur for the well:
• Well 01S10E04C001:
o Exceeds its MT in 12 months out of a total of 660 months (2% of all months) and 4 water years out of a total of 55 water years (7% of all water years).
o The exceedances occur in July of Year 24 in a drought year with exceedances continuing for 7 consecutive months in total, and in August of Year 54 in a drought year with exceedances continuing for 5 consecutive months.

Under the PCBL with demand reductions (PCBL-DR Version 3.0), no representative monitoring network wells exceeded their MTs.

When the demand reduction is included in the ESJWRM, groundwater levels rise across the Subbasin due to the reduction in groundwater pumping from the reduced agricultural areas. Though groundwater levels rise overall, the impact to levels varies from area to area based on the agricultural pumping density. In the PCBL water budget scenario with the demand reduction (PCBL-DR Version 3.0), projections do not show the one well falling below its MT for groundwater levels as compared to the same well in the PCBL Version 3.0 without the demand reduction.

6.3.2 Projected Conditions Baseline with Climate Change and without and with Demand Reduction
Figure 66 shows the location of the two representative monitoring network wells (Well Swenson-3 and Well 01S10E04C001) with projected groundwater levels falling below their MTs for groundwater levels at any point in the 55-year projection of the PCBL with climate change and without demand reductions (PCBL-CC Version ATTACHMENT 2
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3.0). Figure 67 shows the location of the representative monitoring network well with groundwater levels falling below its MT in the PCBL with climate change and with demand reductions (PCBL-CC-DR Version 3.0).

Figure 68 shows the hydrograph of Well Swenson-3. The hydrographs for the other well exceeding its MTs in the PCBL-CC (Well 01S10E04C001) was shown above in Figure 65. The hydrographs have horizontal lines representing the representative monitoring network well’s minimum threshold (red) and measurable objective (green). The ESJWRM model results are shown for the PCBL Version 3.0 (solid blue line), PCBL-DR Version 3.0 (dashed blue line), PCBL-CC Version 3.0 (solid brown line), PCBL-CC-DR Version 3.0 (dashed brown line). Any point these lines cross the red minimum threshold line represents an exceedance in at least one month of the simulation. The hydrographs are discussed in further detail after the figures.

Figure 66: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-CC Version 3.0
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Figure 67: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-CC-DR Version 3.0
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Figure 68: Groundwater Level Hydrograph for Well Swenson-3 Under the PCBL with climate change but without demand reductions (PCBL-CC Version 3.0), two representative monitoring network wells (Well Swenson-3 and Well 01S10E04C001) exceed their MTs. • Well Swenson-3:
o Exceeds its MT in 9 months out of a total of 660 months (1% of all months) and 2 water years out of a total of 55 water years (4% of all water years).
o The exceedances occur in June of Year 54 in a drought year with exceedances continuing for 9 consecutive months in total.
• Well 01S10E04C001:
o Exceeds its MT in 108 months out of a total of 660 months (16% of all months) and 13 water years out of a total of 55 water years (24% of all water years). o The exceedances occur in August of Year 22 in a drought year with exceedances continuing for 3 consecutive water years, in September of Year 26 in a drought year with exceedances continuing for 5 consecutive months, in August of Year 47 in a drought year with exceedances continuing for 3 consecutive water years, and again in November of Year 52 in a drought year with exceedances continuing the remainder of the simulation, or 3 consecutive water years.

Under the PCBL with climate change and with demand reductions (PCBL-CC-DR Version 3.0), no representative monitoring network wells exceeded their MTs.

The demand reduction raises groundwater levels in varying amounts across the Subbasin. As seen with the two wells with MT exceedances in the PCBL-CC Version 3.0, the effects of climate change may continue to significantly impact Subbasin groundwater overdraft and groundwater levels in the future. In the PCBL water budget scenario with the demand reduction and climate change factored in (PCBL-CC-DR Version 3.0), modeling results show no well still falling below their MT for groundwater levels in the 55-year projection.

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6.3.3 Groundwater Levels Undesirable Result
An undesirable result for groundwater levels is considered to occur during GSP implementation when at least 25 percent of representative monitoring network wells (5 of 21 wells in the Subbasin) fall below their MTs for two consecutive years. Figure 69 shows the number of wells with 2 consecutive water years of exceedances in the PCBL Version 3.0, PCBL-DR Version 3.0, PCBL-CC Version 3.0, and PCBL-CC-DR Version 3.0 scenarios over 54 years of the simulation (since Year 1 cannot have 2 consecutive years of exceedances). Table 26 shows the number of water years out of the total possible 54 years with 2 consecutive years of exceedances in the same four simulations. Only the PCBL and PCBL-CC simulations have consecutive water years with MT exceedances occurring in at least one well. These exceedances are all during or immediately following extreme drought conditions. No undesirable results were triggered in any of the four simulations.

Figure 69: Number of Wells with 2 Consecutive Water Years of Exceedances Table 26: Number of Water Years Out of Total with 2 Consecutive Years of Exceedances Number of
Water Years
where Wells
Have 2
Consecutive
Years of
Exceedances
PCBL
Version 3.0
PCBL-DR Version

3.0 PCBL-CC Version

3.0 PCBL-CC-DR
Version 3.0
1 Well 4 0 11 0
2 Wells 0 0 2 0
3 Wells 0 0 0 0
4 Wells 0 0 0 0
5 Wells 0 0 0 0
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7 Projected Conditions Baseline Scenarios with Projects & Management Actions
The goal of this section is to document the Projects & Management Actions (PMAs) selected for simulation in the ESJWRM, the assumptions made about potential project volumes and timing, and results of the model runs. This section is adapted from what was originally developed as a technical memorandum attached to the 2022 Revised GSP (Woodard & Curran, 2022b).

Initially, all the projects from the ESJ Subbasin 2019 GSP and 2022 Sustainable Groundwater Management (SGM) Grant Program’s SGMA Implementation Round 1 application were considered in updates to the 2022 Revised GSP. Based on updates in the Annual Reports and information from representatives of the GSAs in the ESJGBA, these projects were categorized as Category A or B based on how likely they were to be online by 2040 (and likely to advance in the first five years) and if they already had the necessary water rights and/or agreements to proceed with the project. Eight projects were initially sorted into Category A in 2022. Individual meetings with the project proponents in 2022 identified several additional projects that were already moving forward or were already operational; these additional projects were also added to Category A, for a total of 11 projects. GSAs were asked to review and update projects in 2024 and five GSAs reviewed Category A PMAs and provided updates to the project descriptions and volumes to varying degrees. Two projects were added to the Category A projects in 2024, for a total of 13 projects.

7.1 Category A Projects
The Category A projects are added to the information in two existing model runs: PCBL Version 3.0 and PCBLCC Version 3.0. The version of the models including Category A projects are the Projected Condition BaseLine with Category A Projects and Management Actions (PCBL-PMA) and Projected Condition BaseLine with Climate Change and Category A Projects and Management Actions (PCBL-CC-PMA). For these model runs, all projects are assumed to be online and fully operational. Figure 1 shows the general locations of where the delivery of water is expected to occur.

All of the projects discussed below are either in-lieu recharge projects, direct recharge projects, or a combination of the two types, most of which utilize additional surface water coming from the major streams that cross ESJ Subbasin. All of these projects are simulated in ESJWRM as additional surface water diversions in the model. Each project contains a brief description of the proposed version of the project and any assumptions made in simulating the projects in ESJWRM. Since all volumes given below are annual, monthly estimates were assumed by using similar surface water diversions already included in ESJWRM to develop monthly distributions for the annual amounts.

The projects below are listed in no particular order. All information included in this document was the best available estimate at the time and is not necessarily representative of the final design or construction of the projects. Additionally, the Subbasin may choose to pursue projects not included in this technical memorandum in order to meet the needs of SGMA.

In total, 13 Category A projects have been simulated in ESJWRM in the PCBL-PMA Version 3.0 and PCBL-CCPMA Version 3.0. Seven are in-lieu recharge projects, three are direct recharge projects, and three are a combination of in-lieu recharge and direct recharge. Overall, the projects below include in-lieu recharge for agricultural use (9 projects) with deliveries excluding assumed losses with an average of 46,400 acre-feet per year (AFY) (ranging from 9,700-71,100 AFY depending on baseline year type), in-lieu recharge for urban use (1 project) of 5,000 AFY or 20,000 AFY only in Dry and Drought baseline water years, and direct recharge (5 projects) with an average of 24,500 AFY (ranging from 6,500-24,500 AFY depending on baseline year type).

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Note that these project counts include those projects that include components of both in-lieu recharge and direct recharge.

Figure 70: General Location of Category A Projects

7.1.1 SEWD Lake Grupe In-Lieu Recharge
Submitting GSA: Stockton East Water District (SEWD)
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.1.

Project Assumptions Confirmed By: Justin Hopkins (SEWD) on May 9, 2022 and Jeanne Zolezzi (Herum\Crabtree\Suntag) on May 12, 2022. No updated confirmation was received during 2024 model data request.

Project Type: In-Lieu Recharge
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Water Source: The surface water source of this project is from SEWD’s existing contract with the U.S. Bureau of Reclamation (USBR) for the New Hogan Reservoir. Surface water is diverted from the Calaveras River. This is an existing surface water right.

Delivery Area: Approximately 2,500 acres of orchards surrounding Lake Grupe in SEWD Project Overview: The Lake Grupe In-Lieu Recharge Project, proposed by SEWD, is to construct a surface water diversion turn-out on the Calaveras River, upstream of Bellota, and to supply surface water to farms/growers currently using groundwater. The project is to allow about 2,500 acres of orchard crops to irrigate with surface water from Lake Grupe instead of using groundwater. The project would pump water from the Calaveras River and transport to Lake Grupe via a pipeline and ravine, allowing for both the in-lieu banking of groundwater from irrigation conversion and percolation from the ravine used to transport the water. The project was constructed in 2023.

Project Volume: Since the water is transported by a pipeline to Lake Grupe, no evaporation or seepage losses are assumed to occur between Calaveras River and Lake Grupe. The volume of water delivered was assumed by multiplying 1,750 acres (the estimate of acreage for the project from 2022) by an assumed 2.8 acre-feet per acre per year (AF/AY). In situations where there are multiple dry years, the range of water expected is from 0 to 2,000 AFY. Because the baseline water year type Drought represents strings of dry years (water years that were actually part of drought periods), multiple dry years are captured in the Drought deliveries and were assumed to be 2,000 AFY.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 2,000
Range of 0-2,000
AFY in multiple
drought years
Dry 4,900
Normal 4,900
Wet 4,900

7.1.2 SEWD Surface Water Implementation Expansion
Submitting GSA: Stockton East Water District (SEWD)
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.2.

Project Assumptions Confirmed By: Justin Hopkins (SEWD) on May 9, 2022 and Jeanne Zolezzi (Herum\Crabtree\Suntag) on May 12, 2022. No updated confirmation was received during 2024 model data request.

Project Type: In-Lieu Recharge
Water Source: This project relies on water from New Hogan Reservoir (Calaveras River water) and New Melones Reservoir (Stanislaus River water). This is an existing surface water right. SEWD has long-term water supply contracts with USBR for both New Hogan Reservoir and New Melones Reservoir.

Delivery Area: Approximately 6,750 acres adjacent to surface water conveyance systems in SEWD ATTACHMENT 2
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Project Overview: As part of the SEWD Surface Water Implementation Expansion Project, SEWD would require landowners adjacent to surface water conveyance systems (rivers or pipelines) to utilize surface water as part of the SGMA implementation. This would increase surface water usage by about 18,000 to 20,000 AF/year with in-lieu groundwater recharge benefits. Currently, there are about 6,000 acres irrigated with groundwater that could be converted to surface water. There are also an additional 1,500 acres with inactive surface water accounts. SEWD would be the lead agency in environmental/CEQA review and would assist landowners/growers in establishing a turnout for agricultural irrigation and acquiring necessary permits through federal and state regulatory agencies. SEWD has completed the conversion of 2,505 acres to surface water, is in the construction phase to convert an additional 2,592 acres, and in the planning phase to convert an additional 1,135 acres.

Project Volume: Estimated evaporation and seepage losses occurring between Calaveras River or Stanislaus River and SEWD land are incorporated in a separate diversion in ESJWRM. As a conservative estimate, no additional seepage is assumed to occur due to the transport and delivery of this water. The volume of water delivered was estimated by multiplying an estimated 6,750 acres (average of 6,000 and 7,500 acres) by an assumed 2.8 AF/AY and rounding to the nearest thousand. In situations where there are multiple dry years, the range of water expected is from 0 to 4,000 acre-feet per year (AFY). Because the baseline water year type Drought represents strings of dry years (water years that were actually part of drought periods), multiple dry years are captured in the Drought deliveries and were assumed to be 4,000 AFY.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 4,000
Range of 0-4,000
AFY in multiple
drought years
Dry 8,000
Normal 19,000
Wet 19,000

7.1.3 City of Lodi White Slough Water Pollution Control Facility Expansion Note: Information was received from the agency after PCBL-PMA Version 3.0 and PCBL-CC-PMA Version 3.0 were finalized that altered the project description and expected yield for this project. The section below includes the project understanding as it was included in the model simulation. The project updates presented in Chapter 6.2.4.3 are the most current understanding and information will be updated in the modeling for Version 4.0.

Submitting GSA: City of Lodi
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.3.

Project Assumptions Confirmed By: Travis Kahrs (City of Lodi) on May 11, 2022. No updated confirmation was received during 2024 model data request.

Project Type: Recycled Water/In-Lieu Recharge
Water Source: Treated wastewater effluent from White Slough Water Pollution Control Facility Delivery Area: 70-acre pond with capacity of 388 AF and 890 acres of agricultural land surrounding White Slough Pollution Control Facility
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Project Overview: This project includes the construction of a 70-acre pond expansion with a storage capacity of 388 AF. The purpose of this project is to provide tertiary-treated Title 22 effluent for use as irrigation water on approximately 890 acres of agricultural land used to grow crops for dairy cattle, such as corn, wheat, and alfalfa surrounding the White Slough Water Pollution Control Facility (WPCF) to offset groundwater pumping.

Flow will be diverted from Dredger Cut (a dead-end slough of the Sacramento-San Joaquin River Delta) at a rate up to 1,700 gallons per minute over an approximate 75- to 90-day period between October 1 and May 31 of each year. Project studies have demonstrated that the storage provided by this project will significantly offset groundwater pumping through in-lieu use. This project is completed and fully online.

Project Volume: The project is able to store and recharge project year-round due to constant operations of the WPCF. The irrigation season is generally mid-April through September, during which water is provided to 790 acres of agricultural land. In 2020, per the City of Lodi’s 2020 Urban Water Management Plan1, the city used a total of 3,729 AF for agricultural irrigation, with projected volumes to remain the same through at least 2045.

Based on a preliminary Surface Pond Percolation Study22 (completed by Petralogix in 2016), the unlined ponds
were anticipated to have an annual percolation to groundwater rate of up to 29 to 51 million gallons per year or approximately 100 to 200 AFY. With 3,729 AFY expected to be used for agricultural irrigation in the future, the amount of percolation is estimated to be 4% of this amount or about 150 AFY.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 3,729
Dry 3,729
Normal 3,729
Wet 3,729

7.1.4 CSJWCD Capital improvement Program
Submitting GSA: Central San Joaquin Water Conservation District (CSJWCD) Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.4.

Project Assumptions Confirmed By: Reid Roberts (CSJWCD) on May 6, 2022. No updated confirmation was received during 2024 model data request.

Project Type: In-Lieu Recharge
Water Source: This project relies on water from New Melones Reservoir. This is an existing surface water right.

CSJWCD has long-term water supply contracts with USBR for the New Melones Unit Central Valley Project.

Delivery Area: CSJWCD
Project Overview: CSJWCD assists users to convert groundwater-irrigated fields to surface water use. The user applies for water credits based upon new surface water acres. The user is responsible for constructing a diversion facility. As water is diverted, the district reduces the water charge until credit is used or seven years 1 City of Lodi, 2021. 2020 Urban Water Management Plan. August 2021 2 Petralogix, 2016. City of Lodi Surface Pond Percolation Report. September 23, 2016.

ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
since implementation have elapsed. A poll conducted prior to any surface water delivery within the district estimated between 25,000 to 30,000 acres could be brought onto surface water supply. The Capital Improvement Program has been on-going since 1996 and new individual projects are anticipated to begin each year with CSJWCD Board approval and possible streambed alteration permits. Currently, the District takes between 35,000 to 40,000 AFY of its surface water contract to irrigate approximately 15,000 acres. The district has identified an additional 10,000 to 15,000 acres for ongoing expansion of the Capital Improvement Program.

Project Volume: CSJWCD has a contract with USBR for up to 80,000 AFY of Stanislaus River water with a firm yield of 49,000 AFY. In exceptionally dry years (DWR critical years), the district’s allotment is zero. An agreement with City of Stockton gives SEWD the first 15,000 AFY for M&I, so the least CSJWCD is expected to receive in Dry years is 34,000 AFY (49,000 AF – 15,000 AF).

Conservatively, a total of 2 AF/acre was assumed to account for variable water use amounts among different crop types. For Normal and Wet years, an estimated 12,000 acres (assuming a rounded average of the estimated 10,000 to 15,000 acres identified for surface water) were used with the assumed 2 AF/acre water use to determine the annual volume of 24,000 AFY. Considering the District’s firm yield, Dry years are assumed to yield 12,000 AFY as the difference between the existing amount CSJWCD is estimated to receive already in ESJWRM and the 34,000 AFY total the district can expect to receive at minimum.

CSJWCD’s surface water diversions lose an estimated 25-30% on the way to being delivered. This amount will be applied to the diversion in ESJWRM for the calculation of losses due to evaporation and seepage.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 0
Dry 12,000
Normal 24,000
Wet 24,000

7.1.5 NSJWCD South System Modernization
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.5.

Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022. Updated by communication with Jennifer Spaletta (Stoel Rives LLP) and Steve Schwabauer (NSJWCD) on May 13, 2024.

Jennifer Spaletta provided updated text.

Project Type: In-Lieu Recharge/Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing water right held by NSJWCD (Permit 10477).

Delivery Area: NSJWCD South System
Project Overview: This project will modernize the South System Pump and Distribution System to facilitate delivery of additional surface water to farmers in-lieu of groundwater pumping. Pre-2020 deliveries on the South System were 3,000 AFY in wet years (since 1987). NSJWCD has been working on modernizing the South ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
System Pump Station and Distribution System in phases since 2017 to facilitate delivery of 9,000 AFY of additional surface water to farmers in-lieu of groundwater pumping, or for direct recharge. Water would come from NSJWCD Permit 10477 supplies, which are available in about 55 percent of years for irrigation delivery, and in about 80 percent of years for direct recharge. Utilizing just Permit 10477, it is NSJWCD’s goal to deliver maximum wet year quantities of 12,000 AFA through the South System. (Additional deliveries through the South System related to banking with East Bay Municipal Utilities District or EBMUD are discussed in a separate Category A project, “NSJWCD South System Groundwater Banking with EBMUD”).

Project Volume: The volumes for the project tabulated below were provided by Jennifer Spaletta on May 13, 2024 and cover both the NSJWCD South System Modernization as well as the NSJWCD Tecklenburg Recharge Project. In wet and normal years, about 50% of the water will be used for agricultural purposes and 50% for recharge (likely via the Tecklenburg Recharge Project). In critical years, no water is available and in dry years, all of the water is expected to be used for recharge projects. Based on these assumptions, the water was split into the two projects in the table below. The project is expected to be 50% built out by 2028 and fully built out through Phase 4B by 2030.

NSJWCD completed Phases 1 and 2 of this project as well as the Tecklenburg Recharge Basin Project from 2017-2024. Phases 1-2 included a new pump station with two pumps with a total capacity of 30 cfs and replacing key segments of the main distribution pipeline. The Tecklenburg Basin involved purchasing a 10 acre parcel, constructing a basin, and constructing piping to get water in the basin. Phase 3 will be complete by 2025 and includes replacing another segment of the main pipeline and adding a 24 inch lateral to the Tecklenburg basin, which will increase its recharge ability.

Phase 4A and Phase 4B are planned but not yet implemented. Phase 4A involves constructing the Handel Lateral to add delivery capacity to another 1,000 acres in the South System area. The Handel Lateral should be complete by 2027. Phase 4B involves replacing another major section of the main South System Distribution pipeline to remove a delivery bottle-neck in the system and increase capacity for both in-lieu and direct recharge deliveries. Phase 4B should be complete by 2030, if the District secures sufficient funding. The volumes displayed in the table below assume Phase 4B of the project is completed.

Future phases (5, 6, etc) involve additional laterals and improvements along Bear Creek and Pixley Slough to increase surface water diversions for direct recharge and irrigation use (in-lieu recharge). These phases require funding. Other improvements to the South System will include additional recharge basins, on-farm flooding agreements and in-lieu connections for irrigation, which will be installed over time in the next 5-10 years.

The table below shows planned build-out using just the Districts’ Permit 10477 water right. EBMUD Banking water (discussed in “NSJWCD South System Groundwater Banking with EBMUD”) and/or MICUP water under the County’s new water right (Category B project) would be additional supplies beyond what is reflected in the table.

Baseline Water
Year Type
Annual Volume (acre-feet per year or AFY)
Notes
Total South System
Modernization and
Tecklenburg
Recharge Project
South System
Modernization
Tecklenburg
Recharge Project
Drought 0 0 0
Dry 1,500 1,200 300
Normal 9,000 8,000 1,000
Wet 12,000 10,000 2,000
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ESJWRM Version 3.0 October 2024

7.1.6 Long-term Water Transfer to SEWD and CSJWCD
Submitting GSA: South San Joaquin GSA and Oakdale Irrigation District GSA Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.6.

Project Assumptions Confirmed By: Justin Hopkins (SEWD) on May 9, 2022 and Emily Sheldon (Oakdale Irrigation District or OID) on May 9, 2022. In May 2024, updated by Emily Sheldon from OID and Brandon Nakagawa with SSJID.

Project Type: Transfers/In-Lieu Recharge
Water Source: This project relies on water from New Melones Reservoir (Stanislaus River water). This is an existing surface water right (pre-1914) held by Oakdale Irrigation District (OID) and South San Joaquin Irrigation District (SSJID).

Delivery Area: SEWD and CSJWCD
Project Overview: OID and SSJID have historically participated in long-term water transfers of surplus and pre-1914 surface water rights to other entities in the Eastern San Joaquin Subbasin. These transfers have included one-year transfers to CSJWCD as well as a nearly 10-year transfer to SEWD for both agricultural and urban purposes. CSJWCD and SEWD both have surface water available from the USBR’s Central Valley Project on the Stanislaus River; however, project water allocations have become significantly reduced in DWR water year types of below normal and dry years, resulting in increased groundwater reliance to meet annual and permanent crop water demands. Providing long-term water transfers from OID/SSJID to other agencies within ESJ Subbasin would allow for increased average annual surface water deliveries to the Subbasin, reducing groundwater reliance and overdraft within the Subbasin. SEWD and CSJWCD overlie a significant portion of the Subbasin dependent on groundwater and subject to historical overdraft conditions.

No new facilities need to be constructed for this project. Historical transfers have been accomplished through existing facilities, including a tunnel just upstream of the OID/SSJID-owned Goodwin Dam on the Stanislaus River. Transfers from OID/SSJID to SEWD/CSJWCD have historically been agreed to, with historical transfer amounts varying from 0 to 40,000 AF/year. Additional infrastructure may be necessary to increase distribution of surface water supplies to irrigated agriculture and to achieve adequate improvement toward sustainability goals.

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ESJWRM Version 3.0 October 2024
Project funding could be provided directly from the districts participating in water transfers. Additional infrastructure to promote surface water use and capital payments for surface water transfers could be provided indirectly by groundwater reliant entities, thereby providing a means of continuing to utilize groundwater while investing in a Subbasin-wide project that assures continued sustainability within the Subbasin.

Project Volume: The amount and use of the transferred water may vary widely, as SEWD may utilize the supply for either municipal and industrial (M&I) deliveries to Stockton area urban contractors or agricultural customers in SEWD’s district boundaries, while CSJWCD may use the supply for agricultural customers in CSJWCD’s district boundaries. Due to CSJWCD’s firm supply of 49,000 AFY from its New Melones water right and the expansion of surface water use within the District through the Category A project “CSJWCD Capital Improvement Program”, the district is not expected to require additional surface water via water transfer for agricultural customers within the district boundaries. SEWD also has no plans to take transferred water for agricultural purposes due to its Category A “SEWD Surface Water Implementation Expansion.” SEWD expects to receive water from its own water sources during wet and normal years, so transfers of water from SSJID and OID are only expected to occur in critical and dry water years. SEWD has an agreement with the Stockton area urban contractors that a minimum of 20,000 AFY must be supplied for M&I purposes.

The first 15,000 AFY of CSJWCD’s 49,000 AFY allocation is provided to SEWD via an agreement between the districts. In critical years, when CSJWCD’s supply is also zero, SEWD plans to take 20,000 AFY via transferred water to fulfill its urban agreement and 5,000 AFY of transferred water in dry years when 15,000 AFY is available from CSJWCD’s supply. This supply is not guaranteed and SEWD is under no obligation to purchase the water even if SSJID and OID are able to provide water. It is assumed that when the Bureau of Reclamation provides full water allocation to East Side Contractors, no water is anticipated to be transferred.

This project currently only covers the transfer of water from OID and SSJID to SEWD urban customers. Both OID and SSJID may transfer water for agricultural purposes to SEWD and CSJWCD or to other out-of-district users in the future as opportunities arise.

Baseline Water
Year Type
Annual Volume (acre-feet per year or AFY)
Notes M&I to SEWD to
Urban Contractors Agricultural
Drought 20,000 0 (both SEWD and

CSJWCD)
Dry 5,000 0 (both SEWD and

CSJWCD)
Normal 0 0 (both SEWD and

CSJWCD)
Wet 0 0 (both SEWD and

CSJWCD)

7.1.7 NSJWCD South System Groundwater Banking with EBMUD Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.7.

Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022. Updated by communication with Jennifer Spaletta (Stoel Rives LLP) and Steve Schwabauer (NSJWCD) on May 13, 2024.

Jennifer Spaletta provided updated text.

Project Type: In-Lieu Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing water right held by East Bay Municipal Utility District (EBMUD) (Permit 10478) as per Protest Dismissal Agreement from 11/25/2014.

Delivery Area: NSJWCD South System
Project Overview: NSJWCD, EBMUD and other entities in San Joaquin County entered into a Protest Dismissal Agreement in 2014 (the “PDA”) to resolve various water right protests. The PDA Agreement includes a commitment to undertake a pilot level groundwater banking project and a longer-term groundwater banking project. The pilot level banking project is called the “DREAM” project and was just completed in 2024. The DREAM project involved the delivery of 1,000 AF of EBMUD water into the NSJWCD service area along the South System to use for irrigation, effectuating 1,000 AF of in-lieu groundwater recharge. EBMUD received a banked water credit of 50% of the amount of water recharge, not to exceed 500 AF. EBMUD then withdrew its banked water for delivery to the East Bay. The extraction and return of the banked water is subject to a San Joaquin County groundwater export permit.

EBMUD and NSJWCD have started the preliminary planning for the longer-term banking project. The longer-term banking project will use the same concept as the pilot project but will involve larger quantities of water and potential additional facilities to deliver and use the water for direct or in-lieu recharge within NSJWCD, and to extract and return banked water credits to EBMUD. The longer-term project contemplates EBMUD providing surface water supplies between 3,000 AFY to 6,000 AFY in dry years and 8,000 AFY in wet years to NSJWCD. These surface water supplies would come from EBMUD’s water rights on the Mokelumne River and would be in addition to surface water available under NSJWCD’s water right. EBMUD would receive a banked water credit for 50% of the additional supplies provided, leaving a net surface/groundwater increase to the NSJWCD area of 50% of all additional supplies provided. The net water gain to NSJWCD may increase if EBMUD does not extract its banked supplies regularly because of the 5% annual loss factor in the San Joaquin County export ordinance.

As part of both the pilot and longer-term projects, EBMUD is funding facilities in NSJWCD that will be necessary for the banking projects, but can also be used by NSJWCD to deliver NSJWCD’s own surface water supplies. The PDA also provides that the wet year water supplies could be used by SEWD for groundwater banking if they cannot be used in NSJWCD.

Project Volume: The volumes for the project tabulated below were provided by Jennifer Spaletta on May 13, 2024. EBMUD and NSJWCD have started the preliminary planning for the longer-term banking project.

The longer-term project contemplates EBMUD providing surface water supplies between 3,000 AFY to 6,000 AFY in dry years and 8,000 AFY in wet years to NSJWCD. EBMUD would receive a banked water credit for 50% of the additional supplies provided, leaving a net surface/groundwater increase to the NSJWCD area of 50% of all additional supplies provided. The table below only includes the portion that remains in the Subbasin, as the remaining water taken by EBMUD is exported out of the Subbasin.

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ESJWRM Version 3.0 October 2024
Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 0
Dry 750
Normal 3,200 80% of Wet year supply
Wet 4,000

7.1.8 NSJWCD North System Modernization/Lakso Recharge
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.8.

Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022. Updated by communication with Jennifer Spaletta (SToel Rives LLP) and Steve Schwabauer (NSJWCD) on May 13, 2024.

Jennifer Spaletta provided updated text.

Project Type: In-Lieu Recharge/Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing surface water right held by NSJWCD (Permit 10477).

Delivery Area: NSJWCD North System
Project Overview: This project will repair, upgrade and modernize the North System Pump and Distribution System to facilitate delivery of 4,000 to 6,000 AFY of surface water to farmers in-lieu of groundwater pumping and for groundwater recharge. Water would come from NSJWCD Permit 10477 supplies. The Lakso vineyard is located along the existing North System pipeline and includes very sandy soils that are excellent for recharge. The Lakso recharge project involves using a portion of this vineyard for direct recharge and/or Flood MAR. Flood MAR operations could be expanded to additional vineyards and orchards along the North System pipeline.

This project received a 2022 SGMA Implementation Round 1 grant for $3.9 million. Project construction is anticipated to be complete by March 2025. Phase 1A and 1B of this project were completed in 2023-24 to add a new temporary North Pump Station, new pipeline for part of system, and two on-farm recharge projects. NSJWCD expects to connect 200 acres for irrigation in 2024. NSJWCD secured grants for completing a new permanent North Pump Station (Phase 2) which will occur in 2025-2030.

Future phases (3, 4, etc.) will focus on replacing and modernizing the balance of the pipeline distribution system, adding laterals, adding irrigation turnouts/customers, and additional direct recharge locations.

Project Volume: The volumes for the project tabulated below were provided by Jennifer Spaletta on May 13, 2024. The volumes below assume completion of the project through Phase 2, which is estimated to be completed by 2030. Additional phases beyond Phase 2 would require additional funding and would add between 500-1,000 additional AFY to the volumes in the table below.

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ESJWRM Version 3.0 October 2024
Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 0
Dry 1,000
Normal 3,000
Wet 4,000

7.1.9 NSJWCD Tecklenburg Recharge Project
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.9.

Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022. Updated by communication with Jennifer Spaletta (Stoel Rives LLP) and Steve Schwabauer (NSJWCD) on May 13, 2024.

Jennifer Spaletta provided updated text.

Project Type: Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing surface water right held by NSJWCD (Permit 10477).

Delivery Area: NSJWCD South System
Project Overview: NSJWCD constructed and operates a 10-acre recharge pond on the south side of the Mokelumne River on property owned by the Tecklenburg family through a purchase. NSJWCD uses Permit 10477 water available from December 1 through June 30, and not needed for irrigation, for recharge.

Because this project can use water available during the direct diversion flood season, water is expected to be available more frequently under the NSJWCD water right for this project, or 80 percent of years. This project was completed by NSJWCD in 2023-24. The Tecklenburg Basin involved purchasing a 10 acre parcel, constructing a basin, and constructing piping to get water in the basin. A future phase of the larger south system project will add a 24 inch lateral to the Tecklenberg basin, which will increase its recharge ability.

Baseline Water Annual Volume (acre-feet per year or AFY) ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
Year Type Total South System
Modernization and
Tecklenburg
Recharge Project
South System
Modernization
Tecklenburg
Recharge Project Notes
Drought 0 0 0
Dry 1,500 1,200 300
Normal 9,000 8,000 1,000
Wet 12,000 10,000 2,000

7.1.10 City of Stockton Delta Water Treatment Plant Groundwater Recharge Improvements Project
Submitting GSA: City of Stockton
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.10.

Project Assumptions Confirmed By: Received no response to draft assumptions sent out on May 3, 2022 and May 24, 2022. Slight communication from Mitchell Maidrand (City of Stockton) was received during 2024 data request.

Project Type: Direct Recharge
Water Source: Delta Water Treatment Plant
Delivery Area: Recharge basin adjacent to Delta Water Treatment Plant (approximately 70 acres of ponds at buildout in 2040)
Project Overview: The City of Stockton – Municipal Utilities Department (MUD) commissioned the Delta Water Supply Project (DWSP) in 2012 to provide a supplemental surface water supply to its customers. The project included a river diversion pumping station, 12 miles of 54-inch raw water pipeline, a 30 million gallon per day water treatment plant, and six miles of finished water pipelines. This project, located on approximately 60 acres of a larger 130-acre parcel on Lower Sacramento Road, was designed, in part, to protect the groundwater basin through conjunctive management to improve the City’s water supply reliability portfolio.

The original Draft Environmental Impact Report (2005) programmatically evaluated the concept of an Aquifer Storage and Recovery (ASR) project as part of a long-term water resource planning effort for the City. During the design phase, MUD commissioned the Design-Build team to conduct a preliminary groundwater recharge feasibility study of the approximate 70-acre site adjacent to the Delta Water Treatment Plant (DWTP). This study concluded that with available water from the City’s Delta diversion and from Woodbridge Irrigation District, a direct groundwater recharge and recovery project was feasible and recommended additional engineering feasibility and design studies to confirm water availability, recharge infiltration rates, and storage capabilities. The draft study, completed in 2009, is now focused on further evaluation beginning with geotechnical and hydrogeologic effort and groundwater feasibility report to inform a future project phase of implementing a groundwater recharge and recovery project.

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The City is considering the completion of an Underground Storage Supplement through the State Water Resources Control Board for Water Right Permit 21176. Pipeline infrastructure and turnouts will be needed to convey Delta water, diverted under Permit 21176, from the incoming Intake Pump Station 54-inch raw water line to the proposed recharge basin location at the Delta Water Treatment Plant.

This project received a 2022 SGMA Implementation Round 1 grant for $250,000 to conduct a geotechnical investigation of the recharge site to determine the suitability of the site for groundwater recharge and recovery. A feasibility study was completed in December 2023 and determined a recharge potential of approximately 22,000 AFY.

Project Volume: A feasibility memorandum completed in 20091 estimated that Mokelumne River water
purchased from WID as well as City of Lodi stormwater available from the Wilkerson Lateral could be utilized for recharge purposes. An estimated amount of up to 6,500 AFY between March 1 and October 15 would be available from WID, with water assumed to be available only during water year types that are “Wet” or “Above Normal.” Additionally, Lodi stormwater is a potential source for groundwater recharge and an estimated 1,545 AFY is available mostly during winter months when precipitation occurs. The estimated recharge rate at the site was 0.8 AF/day.

In order to expand the use of Permit 21176 water, City of Stockton’s water supply from the San Joaquin River could also be utilized. With an assumed infiltration pond size of 70 acres and a wetted period of 228 days, an estimated 12,768 AFY could potentially be stored to the groundwater basin. Though if water was available during only a 90-day application period, the potential recharge volume would be 5,040 AFY. In the City of Stockton’s water rights petition2, an annual total of 5,102 AFY was estimated to be available for groundwater banking with zero in April through June. Though this project has been called groundwater banking in the past, there are no firm plans to extract water and no more water would be extracted than was recharged. A more detailed technical analysis of the timing and quantity of water supply will be conducted in the future.

In order to be conservative in the estimation of the project’s recharge potential, the lower estimate of 5,040 AFY was assumed. Due to the varying sources of water supply that may be available for recharge (WID water, Lodi stormwater, and Stockton water), water is expected to be able to be recharged year-round.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 5,040
Dry 5,040
Normal 5,040
Wet 5,040

7.1.11 SEWD West Groundwater Recharge Basin
Submitting GSA: Stockton East Water District (SEWD)
1 Swann, B. and Heywood, B., 2009. Draft Memorandum Groundwater Recharge Program Evaluation. March 24, 2009. 2 City of Stockton Water Right Permit 21176 Petition for Extension of Time ATTACHMENT 2
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ESJWRM Version 3.0 October 2024
Project Source: First included as Category A project in 2022 GSP Amendment. Included in 2024 GSP Amendment as Chapter 6.2.4.11.

Project Assumptions Confirmed By: Justin Hopkins (SEWD) on May 9, 2022. No updated confirmation was received during 2024 model data request.

Project Type: Direct Recharge
Water Source: This project relies on water from New Hogan Reservoir (Calaveras River water) and New Melones Reservoir(Stanislaus River water). This is an existing surface water right. SEWD has long-term water supply contracts with USBR for both New Hogan Reservoir and New Melones Reservoir. In addition to Calaveras River and Stanislaus River water, stormwater runoff will also contribute to the volume of water available for recharge.

Delivery Area: Recharge basin near SEWD water treatment plant Project Overview: The United States Army Corps of Engineers (ACOE) plans to excavate dirt to use for levees near the Dr. Joe Waidhofer Water Treatment Plant operated by SEWD. SEWD will use this estimated 100- acre pit once it is created for a new groundwater recharge basin. The recharge at the site was estimated to be about 0.5 feet per day. Construction on the project started in 2024.

Project Volume: Due to the varying sources of water (surface water and stormwater runoff), the project is expected to be able to recharge project year-round.

Baseline Water
Year Type
Annual Volume
(acre-feet per
year or AFY)
Notes
Drought 1,500
Dry 4,000
Normal 16,000
Wet 16,000

7.1.12 NSJWCD Private Pump Partnerships
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source: New project added in 2024 and included in 2024 GSP Amendment as Chapter 6.2.4.12.

Project Assumptions Confirmed By: Communication with Jennifer Spaletta (SToel Rives LLP) and Steve Schwabauer (NSJWCD) on May 13, 2024. Jennifer Spaletta provided text.

Project Type: In-Lieu Recharge/Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing surface water right held by NSJWCD (Permit 10477).

Delivery Area: NSJWCD on both sides of the Mokelumne River Project Overview: This project involves agreements between NSJWCD and existing riparian pumpers along the Mokelumne River to use their existing pumps to pump NSJWCD’s Permit 10477 water for delivery to adjacent non-riparian lands or recharge basins/on-farm recharge. This project leverages existing ATTACHMENT 2
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infrastructure to achieve increased surface water use and reduced groundwater pumping in the district.

NSJWCD is implementing this project for 1 landowner in 2024 for 200 acre and plans to add an additional 200 acre each year for 5 years.

Project Volume: The volumes for the project tabulated below were provided in a document sent by Jennifer Spaletta on May 13, 2024. As a new project, the current delivery volumes are 0 AFY, but by the end of 2024, 1 landowner with 200 acres will be getting 300 AFY in normal years and 600 AFY in dry years. Since the project plans to add an additional 200 acres every year, by 2030 there will be an estimated 1,000 acres of land receiving surface water from private pumps. The estimated volume of water for 1,000 acres is 1,500 AFY in normal years and 3,000 AFY in wet years. The project is not expected to run in drought or dry years.

Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 0
Dry 0
Normal 1,500
Wet 3,000

7.1.13 OID In-Lieu and Direct Recharge Project
Submitting GSA: Oakdale Irrigation District (OID)
Project Source: New project added in 2024 and included in 2024 GSP Amendment as Chapter 6.2.4.13.

Project Assumptions Confirmed By: Communication with Emily Sheldon (OID) on May 15, 2024.

Project Type: In-Lieu Recharge/Direct Recharge
Water Source: This project relies on water from New Melones Reservoir (Stanislaus River water). This is an existing surface water right (pre-1914) held by Oakdale Irrigation District (OID) and South San Joaquin Irrigation District (SSJID).

Delivery Area: Landowners outside of OID’s boundaries to the east Project Overview: The Oakdale Irrigation District In-lieu and Direct Recharge Project is intended to be a cooperative long-term project between OID and landowners to the east of OID’s boundaries within the East Side San Joaquin GSA. The purpose of this project is to allow OID to facilitate surface water deliveries for in-lieu use or direct recharge for East Side San Joaquin GSA landowners during times and conditions that will not impact OID’s existing agricultural customers.

Project Volume: The project envisions the development of up to approximately 25,000 AF of surface water from the Stanislaus River being made available to landowners east of OID’s service area boundaries in both the Eastern San Joaquin and Modesto Subbasins in all, except Critically Dry, water years. Since this project was already included in the PCBL and was calculated using a recent historical average, this PMA doesn’t contribute any additional water in the PCBL-PMA Version 3.0 or PCBL-CC-PMA Version 3.0.

Projected PMA volumes may be revisited in future versions of the model.

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Baseline Water
Year Type
Annual Volume
(acre-feet per year
or AFY)
Notes
Drought 0
Dry 0
Normal 3,000
Wet 3,000

7.2 Assumptions Used to Develop Projected Conditions Baseline Scenarios with Projects & Management Actions
Both models (PCBL-PMA Version 3.0 and PCBL-CC-PMA Version 3.0) share the same input files, excepting those files related to climate change (stream inflows, evapotranspiration, and precipitation). The files relating to the Category A projects simulated as new surface water diversions are identical between the two models. Any differences in the amount of water delivered in the two models are due to differences in agricultural demand and the amount of water available in streams. A summary of the 13 Category A PMAs simulated as additional diversions in both PCBL-PMA Version 3.0 and PCBL-CC- PMA Version 3.0 models is provided in Table 27, along with fractions for recoverable loss (i.e., percolation or canal seepage), nonrecoverable loss (i.e., evaporation), and delivery (i.e., amount delivered is equal to the total amount minus the recoverable and non-recoverable losses). One PMA was already included in the PCBL as Diversion 55 and is also included in Table 27. The remaining 65 PCBL Version 3.0 and PCBL-CC Version 3.0 diversions are summarized in Section 3.2.9.

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Table 27: Summary of ESJWRM Category A Projects Surface Water Deliveries ID Description Diversion
Location Delivery Area Primary Use
Fraction Average Annual
Diversion***
RL* NL** Delivery (acre- feet)
55 OID In-lieu and Direct
Recharge Project
Import
(outside of

ESJWRM)
Landowners outside of
OID’s eastern boundary Ag 0% 0% 100% 3,000
67 Stockton East WD Lake
Grupe In-Lieu Recharge
Calaveras
River
Approximately 1,750 acres
of orchards surrounding
Lake Grupe in SEWD
Ag 0% 0% 100% 4,300
68 Stockton East WD Surface
Water Implementation
Expansion
Import
(outside of

ESJWRM)
Approximately 6,750 acres
adjacent to surface water
conveyance systems in
SEWD
Ag 0% 0% 100% 13,300
69 Stockton East WD West
Groundwater Recharge
Basin
Import
(outside of

ESJWRM)
Recharge basin near
SEWD water treatment
plant
Recharge 100% 0% 0% 10,200
70 Central San Joaquin WCD
Capital improvement
Program
Import
(outside of

ESJWRM)
CSJWCD Ag 15% 2% 83% 20,500
71 Long-term Water Transfer
to Stockton East WD for
M&I
Import
(outside of

ESJWRM)
City of Stockton area
urban users Urban 0% 0% 100% 12,200
72 City of Lodi White Slough
Water Pollution Control
Facility Expansion
Import
(outside of

ESJWRM)
890 acres of agricultural
land surrounding White
Slough Pollution Control
Facility
Ag 4% 2% 94% 3,700
73 North San Joaquin WCD
South System
Modernization
Mokelumne
River NSJWCD South System Ag 0% 0% 100% 6,900
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ID Description Diversion
Location Delivery Area Primary Use
Fraction Average Annual
Diversion***
RL* NL** Delivery (acre- feet)
74 North San Joaquin WCD
Tecklenburg Recharge
Project
Mokelumne
River
Recharge basin located in
NSJWCD South System Recharge 100% 0% 0% 1,300
75 North San Joaquin WCD
South System Groundwater
Banking with EBMUD
Mokelumne
River NSJWCD South System Ag 0% 0% 100% 2,800
76 North San Joaquin WCD
North System
Modernization/Lasko
Recharge
Mokelumne
River NSJWCD North System Ag 50% 0% 50% 4,000
77 City of Stockton Delta
Water Treatment Plant
Groundwater Recharge
Improvements Project
Geotechnical Investigation
Import
(outside of

ESJWRM)
Recharge basin adjacent
to Delta Water Treatment
Plant
Recharge 100% 0% 0% 5,000
82 North San Joaquin WCD
Private Pump Partnerships
Mokelumne
River
Riparian areas along
Mokelumne River within
NSJWCD
Recharge 50% 0% 50% 3,000
*RL = Recoverable Loss (canal seepage or recharge)
**NL = Non-Recoverable Loss (evaporation)
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7.3 Projected Conditions Baseline Scenarios with Category A Projects & Management Actions Results
This section provides a summary of the PCBL-PMA Version 3.0 and PCBL-CC-PMA Version 3.0 model results.

7.3.1 Projected Conditions Baseline with Category A Projects & Management Actions The section below summarizes the results for the PCBL-PMA Version 3.0 as compared to the PCBL Version

3.0. Neither of these runs include climate change.

7.3.1.1 Land and Water Use Water Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual PCBL-PMA Version 3.0 water demand for the Subbasin within the 55-year simulation period is 1,315 TAFY, consisting of approximately 1,153 TAFY of agricultural demand and 162 TAFY of urban demand. This demand is met by an annual average of 572 TAFY of surface water deliveries (493 TAFY of agricultural and 79 TAFY of urban deliveries) and is supplemented by 755 TAFY of groundwater production (687 TAFY of agricultural and 68 TAFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 28 TAFY of surplus in the Subbasin-scale agricultural water supply, which is insignificant relative to the total volume of water use. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus. These annual averages are shown in Table 28. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 71 and Figure 72 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

Table 28 also includes the PCBL Version 3.0 results and a Category A projects benefit calculated as the PCBLPMA Version 3.0 results minus the PCBL Version 3.0 results. The PCBL-PMA Version 3.0 has an average of 41 TAFY more surface water for agricultural purposes and 6 TAFY more surface water for urban areas compared to the PCBL Version 3.0. For urban areas, this represents a reduction in groundwater pumping of 600 AFY. For agricultural areas, the increased surface water results in 34 TAFY less groundwater pumping, a number smaller than the amount of surface water provided due to a mismatch between the Category A water supplied and model-calculated agricultural demand on a monthly basis.

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Table 28: ESJ Subbasin Land and Water Use Budget Annual Average Comparison Between PCBL Version 3.0 and PCBL-PMA Version 3.0
Land and Water Use Budget Component
Annual Average
PCBL Version

3.0 PCBL-PMA
Version 3.0
PMA Benefit
(PCBL-PMA
Version 3.0
minus PCBL
Version 3.0)
Agricultural Area (thousand acres) 365 365 0
Agricultural Demand (TAF) 1,153 1,153 0
Agricultural Groundwater Pumping (TAF) 721 687 -34
Agricultural Surface Water Deliveries (TAF) 452 493 41
Agricultural Surplus (TAF)
1 19 28 8
Urban Area (thousand acres) 129 129 0
Urban Demand (TAF) 156 162 6
Urban Groundwater Pumping (TAF) 67 68 1
Urban Surface Water Deliveries (TAF) 73 79 6
Urban Shortage (TAF)
1 16 16 0
1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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Figure 71: ESJ Subbasin Projected Agricultural Demand in PCBL-PMA Version 3.0 Figure 72: ESJ Subbasin Projected Urban Demand in PCBL-PMA Version 3.0 ATTACHMENT 2
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7.3.1.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

Corresponding to the major hydrologic processes affecting groundwater flow in the Subbasin, these are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) Pumping in the PCBL-PMA Version 3.0 remains the largest component in the groundwater budget with an annual average 766 TAFY. The PCBL-PMA Version 3.0 offsets this pumping with 275 TAFY of deep percolation, a net gain from stream of 223 TAFY, 184 TAFY of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a total subsurface inflow of 75 TAFY. The cumulative change in groundwater storage can be calculated from the annual change in groundwater storage. Due to inherent uncertainties in model input data, calculations, and calibration, all budget components have a degree of uncertainty. Given this uncertainty, the projected longterm average annual groundwater storage deficit in ESJ Subbasin in the PCBL-PMA Version 3.0 is 9 TAFY, indicating that some groundwater overdraft is still occurring even with the Category A projects. These annual averages are shown in Table 29. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 73.

Table 29 also includes the PCBL Version 3.0 results and a Category A projects benefit calculated as the PCBLPMA Version 3.0 results minus the PCBL Version 3.0 results. The results indicate that the Category A projects will resolve the PCBL Version 3.0 Subbasin overdraft condition when impacts due to climate change are not included. Without projects, the modeling shows an average overdraft of 30 TAFY over the 55 years of the PCBL Version 3.0 simulation. With Category A projects in place, the modelling shows a projected overdraft of -9 TAFY on average in the PCBL-PMA Version 3.0. The PCBL-PMA Version 3.0 shows an average increase of 21 TAFY of groundwater in storage when compared to the PCBL Version 3.0. Compared to the PCBL Version 3.0, with Category A projects modeled, the PCBL-PMA Version 3.0 has 33 TAFY less groundwater pumping due to the new in-lieu recharge projects, 19 TAFY more recharge (both direct recharge projects and canal seepage losses for the in-lieu recharge projects), and 17 TAFY less stream seepage into the groundwater system due to higher groundwater levels. Other hydrologic groundwater budget component differences are small between the PCBL Version 3.0 and PCBL-PMA Version 3.0 simulations.

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Table 29: ESJ Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between PCBL Version 3.0 and PCBL-PMA Version 3.0
Hydrologic Groundwater Budget
Component
Annual Average
PCBL
Version 3.0

PCBL-PMA
Version 3.0
PMA Benefit
(PCBL-PMA
Version 3.0
minus PCBL
Version 3.0)
Deep Percolation (TAF) 270 275 5
Deep Percolation of Precipitation (TAF) 55 55 0
Deep Percolation of Applied Water (TAF) 215 220 5
Other Recharge (TAF) 165 184 19
Net Stream Seepage (TAF) 240 223 -17
Net Boundary Inflow (TAF) 94 75 -19
Groundwater Pumping (TAF) 799 766 -33
Change in Groundwater Storage (TAF) -30 -9 21
Figure 73: ESJ Subbasin Projected Hydrologic Groundwater Budget in PCBL-PMA Version

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7.3.2 Projected Conditions Baseline with Climate Change and Category A Projects and Management Actions
The section below summarizes the results for the PCBL-CC-PMA Version 3.0 as compared to the PCBL-CC Version 3.0.

7.3.2.1 Land and Water Use Water Budget
The land and water use budget includes two different versions, agricultural and urban, and represents the balance of the model-calculated water demands with the water supplied. Both the agricultural and urban versions include the same components that make up the water balance:
• Inflows:
o Groundwater pumping
o Surface water deliveries
o Shortage (if applicable)
• Outflows:
o Demand (either agricultural or urban)
o Surplus (if applicable)
The average annual PCBL-CC-PMA Version 3.0 water demand for the Subbasin within the 55-year simulation period is 1,401 TAFY, consisting of approximately 1,238 TAFY of agricultural demand and 162 TAFY of urban demand. This demand is met by an annual average of 572 TAFY of surface water deliveries (493 TAFY of agricultural and 79 TAFY of urban deliveries) and is supplemented by 835 TAFY of groundwater production (767 TAFY of agricultural and 68 TAFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is about 22 TAFY of surplus in the Subbasin scale agricultural water use budget, which is insignificant relative to the total volume of water use. Shortage and surplus represent a misalignment between the reported, estimated, or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus. These annual averages are shown in Table 30. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 74 and Figure 75 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.

Table 30 also includes the PCBL-CC Version 3.0 results and a Category A projects benefit calculated as the PCBL-CC-PMA Version 3.0 results minus the PCBL-CC Version 3.0 results. The PCBL-CC-PMA Version 3.0 has an average of 41 TAFY more surface water for agricultural purposes and 6 TAFY more surface water for urban areas compared to the PCBL-CC Version 3.0. For urban areas, this represents a reduction in groundwater pumping of 600 AFY. For agricultural areas, the increased surface water results in 34 TAFY less groundwater pumping, a number smaller than the amount of surface water provided due to a mismatch between the Category A water supplied and model-calculated agricultural demand on a monthly basis.

Differences between the amount of surface water supplied for PCBL-PMA Version 3.0 and PCBL-CC-PMA Version 3.0 are due to differences in the amount of surface water available in streams impacted by climate change. These differences are small (less than 200 AFY) between results in Table 28 and Table 30.

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Table 30: ESJ Subbasin Land and Water Use Budget Annual Average Comparison Between PCBL-CC Version 3.0 and PCBL-CC-PMA Version 3.0
Land and Water Use Budget
Component
Annual Average

PCBL-CC
Version 3.0

PCBL-CC-PMA
Version 3.0
PMA Benefit
(PCBL-CCPMA Version

3.0 minus

PCBL-CC
Version 3.0)
Agricultural Area (thousand acres) 365 365 0
Agricultural Demand (TAF) 1,240 1,238 -1
Agricultural Groundwater Pumping (TAF) 801 767 -34
Agricultural Surface Water Deliveries
(TAF) 452 493 41
Agricultural Surplus (TAF)1 14 22 8
Urban Area (thousand acres) 129 129 0
Urban Demand (TAF) 156 162 6
Urban Groundwater Pumping (TAF) 67 68 1
Urban Surface Water Deliveries (TAF) 73 79 6
Urban Shortage (TAF)1 16 16 0
1 Shortage and surplus represent a misalignment between the reported, estimated or assumed water supply (groundwater pumping and surface water deliveries) and the calculated demands. In the historical model, this can occur when there are inaccuracies in the reported water supplies or uncertainties in the methodology and/or parameters used to calculate the demand. In the projected conditions, there are uncertainties in the assumptions and parameters used for both monthly supply and demand estimates and/or calculations, resulting in misalignments, which is reported as shortage or surplus.

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Figure 74: ESJ Subbasin Projected Agricultural Demand in the PCBL-CC-PMA Version 3.0 Figure 75: ESJ Subbasin Projected Urban Demand in the PCBL-CC-PMA Version 3.0 ATTACHMENT 2
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7.3.2.2 Hydrologic Groundwater Budget
The primary components of the groundwater budget are the same as represented in the historical model.

Corresponding to the major hydrologic processes affecting groundwater flow in the Subbasin, these are:
• Inflows:
o Deep percolation (from rainfall and irrigation applied water) o Gain from stream (or recharge due to stream seepage)
o Boundary inflow (from surrounding groundwater subbasins and the Sierra Nevada Mountains)
o Other Recharge (from other sources such as irrigation canal seepage, managed aquifer recharge projects, and reservoir seepage)
• Outflows:
o Groundwater pumping
o Loss to stream (or outflow to streams and rivers)
o Boundary outflow (to surrounding groundwater subbasins) o Change in groundwater storage (can be either an inflow or outflow) Pumping in the PCBL-CC-PMA Version 3.0 remains the largest component in the groundwater budget with an annual average 846 TAFY. The PCBL-CC-PMA Version 3.0 offsets this pumping with 274 TAFY of deep percolation, a net gain from stream of 260 TAFY, 187 TAFY of other recharge (includes recharge from unlined canals, reservoir seepage, managed aquifer recharge, and Sierra Nevada Mountain recharge), and a total subsurface inflow of 91 TAFY annually. The cumulative change in groundwater storage can be calculated from the annual change in groundwater storage. Due to inherent uncertainties in model input data, calculations, and calibration, all budget components have a degree of uncertainty. Given this uncertainty, the projected long-term average annual the groundwater storage deficit in ESJ Subbasin in the PCBL-CCPMA Version 3.0 is 34 TAFY, indicating that groundwater overdraft is still occurring even with the Category A projects due to the impacts climate change on the Subbasin. These annual averages are shown in Table

31. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 76.

Table 31 also includes the PCBL Version 3.0 results and a Category A projects benefit calculated as the PCBLPMA Version 3.0 results minus the PCBL Version 3.0 results. While the groundwater storage deficit in the PCBL Version 3.0 is projected to be corrected through the implementation of Category A projects as seen in PCBL-PMA Version 3.0, the modeling shows that when climate change is factored in for the PCBL-CCPMA Version 3.0, there is still additional work (e.g., projects and/or management actions) that may need to be done to maintain subbasin sustainability. The PCBL-CC Version 3.0 has a projected overdraft of 56 TAFY.

When projects are added in, as simulated in PCBL-CC-PMA Version 3.0, this overdraft amount is reduced to 34 TAFY, but still represents continuing groundwater overdraft in the Subbasin that is not sustainable.

Compared to the PCBL-CC Version 3.0, with Category A projects modeled, the PCBL-CC-PMA Version 3.0 has 34 TAFY less groundwater pumping due to the new in-lieu recharge projects, 19 TAFY more recharge (both direct recharge projects and canal seepage losses for the in-lieu recharge projects), and 17 TAFY less stream seepage into the groundwater system due to higher groundwater levels. Other hydrologic ATTACHMENT 2
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groundwater budget component differences are small between the PCBL-CC Version 3.0 and PCBL-CC-PMA Version 3.0 simulations.

Table 31: ESJ Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL-CC and the PCBL-CC-PMA Version 3.0
Hydrologic Groundwater Budget
Component
Annual Average

PCBL-CC PCBL-CC-PMA
Version 3.0
PMA Benefit
(PCBL-CCPMA Version

3.0 minus

PCBL-CC)
Deep Percolation (TAF) 268 274 6
Deep Percolation of Precipitation (TAF) 52 52 0
Deep Percolation of Applied Water (TAF) 216 222 6
Other Recharge (TAF) 168 187 19
Net Stream Seepage (TAF) 276 260 -17
Net Boundary Inflow (TAF) 111 91 -20
Groundwater Pumping (TAF) 879 846 -34
Change in Groundwater Storage (TAF) -56 -34 22
Figure 76: ESJ Subbasin Projected Hydrologic Groundwater Budget in the PCBL-CC-PMA Version 3.0
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7.4 Projected Conditions Baseline Scenarios with Category A Projects & Management Actions Groundwater Level Hydrographs
In order to evaluate how the chronic lowering of groundwater levels sustainability indicator might be impacted by Subbasin projected conditions, including climate change and Category A projects, groundwater hydrographs were analyzed for the 21 representative monitoring network wells selected in the GSP to monitor Subbasin groundwater levels. The goal of this analysis was to see where, when, and how often these groundwater hydrographs exceeded the minimum thresholds (MTs) established in the GSP. An undesirable result for groundwater levels as established in the GSP and refined in 2022 edits is when at least 25 percent of representative monitoring network wells (5 out of 21 wells) for the Subbasin are projected to exceed established minimum thresholds for two consecutive years. Figure 62 shows the location of these 21 representative monitoring network wells identified in the GSP as the monitoring network for the chronic lowering of groundwater levels.

Groundwater level hydrographs at the 21 representative monitoring network wells were used to evaluate the impacts of the Category A Projects under the PCBL-PMA Version 3.0 and PCBL-CC-PMA Version 3.0 as compared to the PCBL Version 3.0 and PCBL-CC Version 3.0, respectively. Two representative monitoring network wells (Well Swenson-3, and Well 01S10E04C001) reported groundwater levels below their minimum thresholds for at least one month in any of the models evaluated (PCBL Version 3.0, PCBL- PMA Version 3.0, PCBL-CC Version 3.0, and PCBL-CC-PMA Version 3.0). The hydrographs of these two representative monitoring network wells are shown and discussed in Sections 3.3.1 and 3.3.2. Subbasin undesirable results for groundwater levels are discussed in Section 3.3.3.

7.4.1 Projected Conditions Baseline without and with Category A Projects and Management Actions
Figure 63 shows the location of the representative monitoring network well (Well 01S10E04C001) with groundwater levels below its minimum threshold at any point in the 55-year projection of the PCBL Version

3.0 (without climate change or Category A projects). Figure 77 shows the location of the representative monitoring network wells with groundwater levels below their MT in the PCBL-PMA Version 3.0. Figure 78 shows the hydrograph of Well 01S10E04C001. The hydrographs have horizontal lines representing the representative monitoring network well’s minimum threshold (red) and measurable objective (green). The ESJWRM model results are shown for the PCBL Version 3.0 (solid blue line), PCBL-PMA Version 3.0 (dotted blue line), PCBL-CC Version 3.0 (solid brown line), PCBL-CC-PMA Version 3.0 (dotted brown line). Any point these lines cross the red minimum threshold line represents an exceedance in at least one month of the simulation. The hydrographs are discussed in further detail after the figures.

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Figure 77: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in PCBL-PMA Version 3.0
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Figure 78: Groundwater Level Hydrograph for Well 01S10E04C001 Under the PCBL Version 3.0 (without climate change or Category A projects), the representative monitoring network well with its hydrograph shown above in Figure 78 (Well 01S10E04C00) exceed its minimum threshold. The text below discusses when and how often MT exceedances occur for the well:
• Well 01S10E04C001:
o Exceeds its MT in 12 months out of a total of 660 months (2% of all months) and 4 water years out of a total of 55 water years (7% of all water years). o The exceedances occur in July of Year 24 in a drought year with exceedances continuing for 7 consecutive months in total, and in August of Year 54 in a drought year with exceedances continuing for 5 consecutive months.

Under the PCBL with Category A projects (PCBL-PMA Version 3.0), no representative monitoring network wells exceeded their MTs.

When Category A projects are included in the ESJWRM, groundwater levels rise across the Subbasin due to the additional groundwater recharge projects and reduction in groundwater pumping from additional surface water diversions. Though groundwater levels rise overall, the impact to levels varies from area to area based on proximity to the Category A projects. In the PCBL Version 3.0 water budget scenario with projects included (PCBL-PMA Version 3.0), projections show no wells falling below their minimum thresholds for groundwater levels as compared to the one well in the PCBL Version 3.0 without Category A projects. In other words, the Category A projects caused one well that was exceeding its MT in the PCBL Version 3.0 to no longer exceed its MT the PCBL-PMA Version 3.0. This well, located in the southeast portion of the subbasin, has groundwater levels increasing due to the Category A projects occurring across the subbasin.

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7.4.2 Projected Conditions Baseline with Climate Change and without and with Category A Projects and Management Actions
Figure 66 shows the location of the two representative monitoring network wells (Well Swenson-3 and Well 01S10E04C001) with projected groundwater levels falling below their MTs for groundwater levels at any point in the 55-year projection of the PCBL with climate change and without Category A projects (PCBL-CC Version 3.0). Figure 79 shows the location of the representative monitoring network wells with groundwater levels falling below their MTs in the PCBL with climate change and with Category A projects (PCBL-CC-PMA Version 3.0).

Figure 80 shows the hydrograph of Well Swenson-3. The hydrograph for the other well exceeding its MTs in the PCBL-CC Version 3.0 was shown above in Figure 78. The hydrographs have horizontal lines representing the representative monitoring network well’s minimum threshold (red) and measurable objective (green). The ESJWRM model results are shown for the PCBL Version 3.0 (solid blue line), PCBLPMA Version 3.0 (dotted blue line), PCBL-CC Version 3.0 (solid brown line), PCBL-CC-PMA Version 3.0 (dotted brown line). Any point these lines cross the red minimum threshold line represents an exceedance in at least one month of the simulation. The hydrographs are discussed in further detail after the figures.

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Figure 79: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-CC-PMA Version 3.0
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Figure 80: Groundwater Level Hydrograph for Well Swenson-3 Under the PCBL with climate change but without Category A projects (PCBL-CC Version 3.0), both representative monitoring network wells (Well Swenson-3 and Well 01S10E04C001) exceed their MTs. • Well Swenson-3:
o Exceeds its MT in 9 months out of a total of 660 months (1% of all months) and 2 water years out of a total of 55 water years (4% of all water years). o The exceedances occur in June of Year 54 in a drought year with exceedances continuing for 9 consecutive months in total.
• Well 01S10E04C001:
o Exceeds its MT in 108 months out of a total of 660 months (16% of all months) and 13 water years out of a total of 55 water years (24% of all water years). o The exceedances occur in August of Year 22 in a drought year with exceedances continuing for 3 consecutive water years, in September of Year 26 in a drought year with exceedances continuing for 5 consecutive months, in August of Year 47 in a drought year with exceedances continuing for 3 consecutive water years, and again in November of Year 52 in a drought year with exceedances continuing the remainder of the simulation, or 3 consecutive water years.

Under the PCBL with climate change and with Category A projects (PCBL-CC-PMA Version 3.0), no representative monitoring network wells exceeded their MTs.

Category A projects raise groundwater levels in varying amounts across the Subbasin. As seen with the two wells with MT exceedances in the PCBL-CC Version 3.0, the effects of climate change may continue to significantly impact Subbasin groundwater overdraft and groundwater levels in the future. In the PCBL water budget scenario with projects and climate change factored in (PCBL-CC-PMA Version 3.0), modeling results showed an improvement in groundwater levels in the 55-year projection, with no representative monitoring network wells falling below their MTs.

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7.4.3 Groundwater Levels Undesirable Result
An undesirable result for groundwater levels is considered to occur during GSP implementation when at least 25 percent of representative monitoring network wells (5 of 21 wells in the Subbasin) fall below their MTs for two consecutive years. Figure 81 shows the number of wells with 2 consecutive water years of exceedances in the PCBL Version 3.0, PCBL-CC Version 3.0, PCBL-PMA Version 3.0, and PCBL-CC-PMA Version 3.0 models over 54 years of the simulation (since Year 1 cannot have 2 consecutive years of exceedances). Table 32 shows the number of water years out of the total possible 54 years with 2 consecutive years of exceedances in the same four simulations. Only the PCBL Version 3.0 and PCBL-CC Version 3.0 simulations have consecutive water years with MT exceedances occurring in at least one well.

These exceedances are all during or immediately following extreme drought conditions. No undesirable results were triggered in any of the four simulations.

Figure 81: Number of Wells with 2 Consecutive Water Years of Exceedances Table 32: Number of Water Years Out of Total with 2 Consecutive Years of Exceedances Number of
Water Years
where Wells
Have 2
Consecutive
Years of
Exceedances
PCBL
Version 3.0

PCBL-PMA
Version 3.0
PCBL-CC Version

3.0 PCBL-CC-PMA
Version 3.0
1 Well 4 0 11 0
2 Wells 0 0 2 0
3 Wells 0 0 0 0
4 Wells 0 0 0 0
5 Wells 0 0 0 0
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8 Conclusions and Recommendations
The updated Historical ESJWRM Version 3.0 is a robust, comprehensive, defensible, and well-established integrated water resources model for assessing the water resources in the ESJ Subbasin under historical and projected conditions using PCBL Version 3.0. The following recommendations are to be considered for further refinements and enhancements of the model:
• Continue engagement with local groundwater users and managers. Continue working with local agencies and groundwater users in ESJ Subbasin to further understand the local operations of the groundwater system and improve representation of groundwater users in the ESJWRM. • Enhance variability of potential evapotranspiration. The current version of the IDC used for estimation of the consumptive use of crops in the ESJWRM uses monthly potential ET values that are the same for all years during the model period. Given that there may be annual variability in the potential ET data with possible effects on the annual estimation of crop water demand, it is recommended to use more detailed data with temporal variability to develop a full time series of ET values for use in the model. With the widespread availability of evapotranspiration data sources (e.g., ITRC, Formations Environmental, Cal-SIMETAW, OpenET), the ESJGWA plans to review available sources and determine a dataset to use for inclusion in ESJWRM. • Update information from C2VSimFG. Many datasets in ESJWRM relied on DWR’s C2VSimFG (unreleased version from approximately 2017) for information on the unsaturated zone, small watersheds, rainfall-runoff patterns, and more. C2VSimFG has since been updated and continues to undergo revisions to better represent the California Central Valey. ESJWRM may benefit from further examination of and potentially updates to the datasets from C2VSimFG. • Refine information for Cosumnes and Modesto Subbasins. Now that the neighboring subbasins to ESJ Subbasin all have established GSPs and local models, coordination with the neighboring GSAs could improve ESJWRM by updating Cosumnes and Modesto Subbasins water supply and demand or pulling boundary conditions along the borders with ESJ Subbasin using the neighboring local models.
• Climate change refinement. The climate change approach is based on the methodology in DWR’s guidance document (DWR, 2018a) and uses “best available information” related to climate change in the Subbasin. There are limitations and uncertainties associated with the analysis. One important limitation is that CalSim II does not fully simulate local surface water operations. Thus, the analysis conducted for this GSP may not fully reflect how surface and groundwater basin operations would respond to the changes in water demand and availability caused by climate change. Mokelumne River flows are simulated in PCBL-CC as unimpaired despite the potential of changes to operations for Pardee and Camanche Reservoirs under climate change conditions. This presents an opportunity in future efforts to improve the analysis to better project streamflow. Use of a local model and the perturbation factor approach were deemed appropriate given the uncertainties in the climate change analysis. DWR may refine climate change information in the further and necessitate an update to the approach used in ESJWRM.
• Calaveras River seepage. The current version (Version 3.0) of the Historical ESJWRM model incorporated and was calibrated using the best data and information available at the time it was updated. A GSA has since brought forward new information on Calaveras River seepage that may complement information in the ESJWRM. Based on this information received, the ESJGWA will perform further analysis to have a better estimate of the historical river seepage, which should help ATTACHMENT 2
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improve the model calibration. Once the model is recalibrated, the projected condition modeling work will be re-evaluated. These potential changes to Calaveras River seepage may also potentially have impacts on the estimates of sustainable yield. ESJWRM has been and continues to be a useful analysis tool that has supported the ESJGWA in development and maintenance of the GSP and other policy measures. As with all analysis tools, ESJWRM is a living model that undergoes further refinements as data gaps are filled and new and updated information becomes available to support further understanding of the subbasin’s hydrogeology and operational conditions, which in turn helps develop more robust information in support of the Subbasin’s GSP and path to sustainability.

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9 References
Department of Water Resources. 2016. Best Management Practices for the Sustainable Management of Groundwater Water Budget.

Department of Water Resources (DWR). 2018a. Guidance for Climate Change Data Use During Groundwater Sustainability Plan Development.

Department of Water Resources (DWR). 2018b. SGMA Data Viewer.

Department of Water Resources (DWR). 2023. California Airborne Electromagnetic Surveys for the Cosumnes, Tracy, Eastern San Joaquin, and East Contra Costa Subbasins, and Livermore Valley Groundwater Basin.

Department of Water Resources (DWR). Statewide Crop Mapping. Downloaded for groundwater subbasins in model area. https://gis.water.ca.gov/app/CADWRLandUseViewer/.

Department of Water Resources (DWR) California Data Exchange Center (CDEC). San Joaquin Valley Water Year Hydrologic Classification Index. http://cdec.water.ca.gov/cgi-progs/iodir/WSIHIST.

Dogrul, Emin C. and Tariq N. Kadir (2024a). Integrated Water Flow Model User’s Manual (IWFM-2015), Revision 1443. Bay-Delta Office, California Department of Water Resources. April 2024. https://data.cnra.ca.gov/dataset/iwfm-integrated-water-flow-model/resource/311462d8-6cb5-4259- bd2c-c1e36a5475be.

Dogrul, Emin C. and Tariq N. Kadir (2024b). Integrated Water Flow Model Theoretical Documentation (IWFM-2015), Revision 1443. Bay-Delta Office, California Department of Water Resources. April 2024. https://data.cnra.ca.gov/dataset/iwfm-integrated-water-flow-model/resource/311462d8-6cb5-4259- bd2c-c1e36a5475be.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2019. Eastern San Joaquin Groundwater Subbasin Groundwater Sustainability Plan. November 2019.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2020. Eastern San Joaquin Groundwater Subbasin Water Year 2019 Annual Report. April 2020.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2021. Eastern San Joaquin Groundwater Subbasin Water Year 2020 Annual Report. April 2021.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2022a. Eastern San Joaquin Groundwater Subbasin Water Year 2021 Annual Report. March 2022.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2022b. Revised Eastern San Joaquin Groundwater Subbasin Groundwater Sustainability Plan. June 2022.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2023. Eastern San Joaquin Groundwater Subbasin Water Year 2022 Annual Report. March 2023.

Eastern San Joaquin Groundwater Authority (ESJGWA). 2024. Eastern San Joaquin Groundwater Subbasin Water Year 2023 Annual Report. March 2024.

Faunt, C.C. 2012. Extent of Corcoran Clay modified from Page (1986) for the Central Valley Hydrologic Model (CVHM): U.S. Geological Survey data release, https://doi.org/10.5066/P983J3B3.

Oregon State University (OSU). PRISM Climate Group. http://prism.oregonstate.edu.

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Page, R.W. 1974. Base and Thickness of the Post-Eocene Continental Deposits in the Sacramento Valley, California. USGS Water-Resources Investigations Report 73-45.

Williamson, A.K., D.E. Prudic, and L.A. Swain. 1989. Ground-water flow in the Central Valley, California. USGS Professional Paper 1401-D.

Woodard & Curran. 2018a. Eastern San Joaquin Water Resources Model (ESJWRM) Final Report. August 2018.

Woodard & Curran. 2018b. Eastern San Joaquin Water Resources Model Agricultural and Urban Demand Estimates Technical Memorandum. February 2018.

Woodard & Curran. 2022a. Eastern San Joaquin Water Resources Model (ESJWRM) Version 2.0 Update.

Updated Draft June 2022.

Woodard & Curran. 2022b. Assumptions and Results for Category A Projects in ESJWRM. Draft June 2, 2022.

Woodard & Curran. 2022c. Demand Reduction Analysis in ESJWRM Technical Memorandum. Draft June 2, 2022.

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Groundwater Sustainability Plan Amendment
Complete Appendices November 2024
APPENDIX 3-A.

CONSULTATION INITIATION LETTER FROM THE

CALIFORNIA DEPARTMENT OF WATER RESOURCES TO

THE EASTERN SAN JOAQUIN PLAN ADMINISTRATOR
ENTITLED "EASTERN SAN JOAQUIN SUBBASIN - 2020
GROUNDWATER SUSTAINABILITY PLAN," DATED
NOVEMBER 18, 2021
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CALIFORNIA DEPARTMENT OF WATER RESOURCES

SUSTAINABLE GROUNDWATER

Eastern San Joaquin Subbasin Plan Administrator
1810 E. Hazelton Avenue, Stockton, CA 95201
[email protected]
RE: Eastern San Joaquin Subbasin - 2020 Groundwater Sustainability Plan Dear Kris Balaji,
The Eastern San Joaquin Groundwater Authority submitted the Eastern San Joaquin Groundwater Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) to the Department of Water Resources (Department) for evaluation and assessment as required by the Sustainable Groundwater Management Act (SGMA).1 Department staff have substantially completed an initial review of the GSP and have identified potential deficiencies (see the enclosed document) which may preclude the Department’s approval.2 Department staff have also developed potential corrective actions3 for each potential deficiency. The potential deficiencies do not necessarily represent all deficiencies or discrepancies that the Department may identify in the GSP but focus on those deficiencies that staff believe, if not addressed, could lead to a determination that the GSP is incomplete or inadequate.4 This letter initiates consultation between the Department, the Plan Manager, and the Subbasin’s 15 groundwater sustainability agencies (GSAs) regarding the amount of time needed to address the potential deficiencies and corrective actions. The Department will issue a final determination as described under the GSP Regulations5 no later than January 29, 2022.

If the Department determines the GSP to be incomplete, the deficiencies precluding approval would need to be addressed within a period not to exceed 180 days from the 1 Water Code § 10720 et seq.
2 23 CCR § 355.2(e)(2).
3 23 CCR § 355.2(e)(2)(B). 4 The Department recognizes that litigation regarding the GSP has been filed. The filing of litigation does not alter or affect the Department’s mandate to issue its final assessment of the Agency’s groundwater sustainability plan (GSP or Plan) for the basin within two years of its submission. (Water Code §10733.4(d).) Furthermore, the Department’s assessment will consist of a technical review of the submitted Plan, as required by SGMA and the GSP Regulations, and the filing of the litigation did not in any way influence or affect the Department’s evaluation of the Plan. The Department expresses no opinion on the claims of the parties in the pending litigation involving the GSP. 5 23 CCR Division 2, Chapter 1.5, Subchapter 2.

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determination. A determination of incomplete would allow the GSAs to formally address identified deficiencies and submit a revised GSP to the Department for further review and evaluation. Department staff will contact you before making the final determination to discuss the potential deficiencies and the amount of time needed by the GSAs to address the potential corrective actions detailed in the enclosed document.

Materials submitted to the Department to address deficiencies must be part of the GSP.

The GSAs must justify that any materials submitted are part of the revised GSP; this justification is also part of the submittal. To facilitate the Department’s review of the revised GSP, the GSAs should also provide a companion document with tracked changes of modifications made to address deficiencies. The GSAs must submit the revised GSP through the DWR SGMA Portal where, as is currently available, interested parties may provide comments on submitted materials to the Department.

Department staff will work expeditiously to review materials submitted to address deficiencies and to evaluate compliance of the revised GSP. The Department will keep a GSP status designated as incomplete during its review of the submitted materials. The Department could subsequently approve an incomplete GSP if the GSAs have taken corrective actions to address deficiencies identified by the Department within a period not to exceed 180 days from the determination. The Department could also issue a determination of inadequate for an incomplete GSP if the Department, after consultation with the State Water Resources Control Board, determines the GSAs have not taken sufficient actions to correct the deficiencies identified by the Department.

If you have any questions, please do not hesitate to contact the Sustainable Groundwater Management Office staff by emailing [email protected].

Thank you,
Paul Gosselin
Deputy Director for Sustainable Groundwater Management
Enclosure:

1. Potential Deficiencies and Corrective Actions
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Potential Deficiencies and Corrective Actions
Department of Water Resources (Department) staff have identified deficiencies regarding the Eastern San Joaquin Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) that may preclude the Department’s approval. Therefore, consistent with the GSP Regulations, Department staff are considering corrective actions the Subbasin’s groundwater sustainability agencies (GSAs) should review to determine whether and how the deficiencies can be addressed. The deficiencies and potential corrective actions are explained below, including the general regulatory background, the specific deficiencies identified in the GSP, and specific actions to address the deficiencies. The specific actions identified are potential corrective actions until the Department makes a final determination.

General Background
Potential deficiencies identified in the Eastern San Joaquin Subbasin GSP relate to the development and documentation of sustainable management criteria, including undesirable results and minimum thresholds that define when undesirable results may occur.

The Department's GSP Regulations describe several required elements of a GSP under the heading of “Sustainable Management Criteria”6, including undesirable results, minimum thresholds, and measurable objectives. These components of sustainable management criteria must be quantified so that GSAs, the Department, and other interested parties can monitor progress towards sustainability in a basin consistently and objectively.

A GSA relies on local experience, public outreach and involvement, and information about the basin it has described in the GSP basin setting (i.e., the hydrogeologic conceptual model, the description of current and historical groundwater conditions, and the water budget), among other factors, to develop criteria for defining undesirable results and setting minimum thresholds and measurable objectives.7
The Sustainable Groundwater Management Act (SGMA) defines sustainable groundwater management as the management and use of groundwater in a manner that can be maintained during the planning and implementation horizon without causing undesirable results.8 Avoidance of undesirable results is thus explicitly part of sustainable groundwater management as established by SGMA and critical to the success of a GSP.

The definition of undesirable results is critical to establishing an objective method to define and measure sustainability for a basin. As an initial matter, SGMA provides a 6 23 CCR § Article 5, Subarticle 3. 7 23 CCR §§ 354.8, 354.10, 354.12 et seq. 8 Water Code § 10721(v).

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qualitative definition of undesirable results as “one or more” of six specific “effects caused by groundwater conditions occurring throughout the basin.”9 GSAs define, in their GSPs, the specific significant and unreasonable effects that would constitute undesirable results and the groundwater conditions that would produce those results in their basins.10 The GSAs’ definition must include a description of the processes and criteria relied upon to define undesirable results and describe the effect of undesirable results on the beneficial uses and users of groundwater, surface land uses (for subsidence), and surface water (for interconnected surface water).11 SGMA leaves the task of establishing undesirable results and setting thresholds largely to the discretion of the GSAs, subject to review by the Department. In its review, the Department requires a thorough and reasonable analysis of the groundwater conditions and the associated effects the GSAs must manage the groundwater basin to avoid, and the GSAs’ stated rationale for setting objective and quantitative sustainable management criteria to prevent those undesirable conditions from occurring.12 If a GSP does not meet this requirement, the Department cannot evaluate the GSAs’ likelihood of achieving their sustainability goal. That does not necessarily mean that the GSP or its objectives are inherently unreasonable; rather, the Department cannot evaluate whether the GSP's implementation would successfully achieve sustainable management if it is unclear what undesirable conditions the GSAs seek to avoid.

Potential Deficiency 1. The GSP lacks sufficient justification for identifying that undesirable results for chronic lowering of groundwater levels, subsidence, and depletion of interconnected surface waters can only occur in consecutive non-dry water year types. The GSP also lacks sufficient explanation for its chronic lowering of groundwater levels minimum thresholds and undesirable results.

The first potential deficiency relates to the GSP’s requirement of two consecutive non-dry (i.e., below normal, above normal, or wet) water-year types and the exclusion of dry and critically dry water-year types in the identification of undesirable results for chronic lowering of groundwater levels, and, by proxy, land subsidence and depletions of interconnected surface water.

Background
Related to this potential deficiency, SGMA defines the term “Undesirable Result,” in part, as one or more of the following effects caused by groundwater conditions occurring throughout the basin:13
9 Water Code § 10721(x). 10 California Department of Water Resources, Best Management Practices for the Sustainable Management of Groundwater: Sustainable Management Criteria (Draft), November 2017. 11 23 CCR §§ 354.26(b), 354.28(c)(5), 354.28(c)(6).
12 23 CCR § 355.4(b)(1).
13 Water Code § 10721(x).

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• Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon.

Overdraft during a period of drought is not sufficient to establish a chronic lowering of groundwater levels if extractions and groundwater recharge are managed as necessary to ensure that reductions in groundwater levels or storage during a period of drought are offset by increases in groundwater levels or storage during other periods.
• Significant and unreasonable land subsidence that substantially interferes with surface land uses.
• Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water.

Potential Deficiency Details
Department staff identified two areas of concern, described below, which, if not addressed, may preclude approval of the GSP. Regarding the first area of concern, the GSP identifies that an undesirable result occurs “when at least 25 percent of representative monitoring wells used to monitor groundwater levels (5 of 20 wells in the Subbasin) fall below their minimum level thresholds for two consecutive years that are categorized as non-dry years (below-normal, above-normal, or wet), according to the San Joaquin Valley Water Year Hydrologic Classification.” The GSP further states that “the lowering of groundwater levels during consecutive dry or critically-dry years is not considered to be unreasonable, and would therefore not be considered an undesirable result, unless the levels do not rebound to above the thresholds following those consecutive non-dry years.”14
Department staff find that the water-year type requirement in the definition of the undesirable result for chronic lowering of groundwater levels (i.e., two consecutive nondry years) is not consistent with the intent of SGMA. The water-year type requirement could potentially allow for unmanaged and continued lowering of groundwater levels under certain hydrologic or climatic conditions that have occurred historically. A review of historical San Joaquin Valley water-year type classifications15 indicates the potential for dry periods without the occurrence of a second consecutive non-dry year to persist for greater than ten years (see, e.g., the 11 years from water years 1985 through 1995).

Department staff also note that concurrent below normal, above normal, or wet years occurred in only five of the last twenty water years from 2001 through 2020. Because of this definition, GSAs in the Subbasin could disregard potential impacts of groundwater level declines below the minimum thresholds during extended periods of dry years, even if interrupted by normal or wet years.
14 ESJ GSP, p. 253. 15 Chronological Reconstructed Sacramento and San Joaquin Valley Water Year Hydrologic Classification Indices, Water Year 1901 through 2020. California Department of Water Resources, https://cdec.water.ca.gov/reportapp/javareports?name=WSIHIST.

For example, while describing measurable objectives for groundwater levels, the GSP states, “the margin of operational flexibility is intended to accommodate droughts, climate change, conjunctive use operations, or other groundwater management activities. The margin of operational flexibility is defined as the difference between the minimum threshold and the measurable objective.”16 Based on these statements, it appears the minimum thresholds already accommodate drought conditions, so it is unclear why the GSP's definition of undesirable results further excludes minimum threshold exceedances during dry water years. (See Potential Corrective Action 1a.) SGMA states that “overdraft during a period of drought is not sufficient to establish a chronic lowering of groundwater levels if extractions and groundwater recharge are managed as necessary to ensure that reductions in groundwater levels or storage during a period of drought are offset by increases in groundwater levels or storage during other periods.”17 If the GSAs intended to incorporate this concept into their definition of the undesirable result for chronic lowering of groundwater levels, the GSP fails to identify specific extraction and groundwater recharge management actions the GSAs would implement18 or otherwise describe how the Subbasin would be managed to offset, by increases in groundwater levels or storage during other periods, dry year reductions of groundwater storage. The GSP identifies many projects that, once implemented, may lead to the elimination of long-term overdraft conditions in the Subbasin. However, the GSP does not sufficiently detail how projects and management actions, in conjunction with the proposed chronic lowering of groundwater levels sustainable management criteria, will offset drought-related groundwater reductions and avoid significant and unreasonable impacts when groundwater level minimum thresholds are potentially exceeded for an extended period in the absence of two consecutive non-dry years. (See Potential Corrective Action 1b.)
As noted above, the GSP states that minimum thresholds developed for chronic lowering of groundwater levels serve as proxies for subsidence19 and depletion of interconnected surface waters.
20 Therefore, Department staff assume the GSAs intend to apply the same water-year type criteria to undesirable results for those sustainability indicators (i.e., land subsidence or depletion of interconnected surface water undesirable results do not occur until groundwater levels exceed the thresholds for two consecutive non-dry water years).

However, where SGMA acknowledges that groundwater level declines during drought periods are not sufficient to cause an undesirable result for chronic lowering of groundwater levels, the statute does not similarly provide an exception for subsidence or stream depletion during periods of drought. (See Potential Corrective Action 1c.) 16 ESJ GSP, p. 259. 17 Water Code § 10721(x)(1). 18 23 CCR § 354.44(b)(9). 19 ESJ GSP, p. 270. 20 ESJ GSP, p. 271.

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Department staff's second area of concern is the GSP's evaluation of the effects of the proposed minimum thresholds and undesirable results on beneficial uses and users of groundwater. The GSP identifies that the chronic lowering of groundwater levels could cause undesirable results from wells going dry, reductions in pumping capacities, increased pumping costs, the need for deeper well installations or lowering of pumps, and adverse impacts to environmental uses and users.21 The GSP builds an analysis of domestic wells going dry into its minimum thresholds, thereby considering the factors of wells going dry and the need for deeper well installations. However, it does not address how the management criteria address the other factors identified by the GSAs as potential undesirable results, including reductions in pumping capacity or increased pumping costs for shallow groundwater users, or adverse impacts to environmental uses and users.

The GSAs set minimum thresholds in the Subbasin at the shallower of the 10th percentile domestic [or municipal] well depth or the historical low groundwater levels with a subtracted buffer value, which the GSP states allows for operational flexibility. 22 These
minimum threshold values generally allow groundwater levels to decline below historic lows; minimum thresholds defined using the buffer value approach allow twice the historical drawdown from the shallowest recorded groundwater levels. 23 Aside from the
GSP's domestic well analysis, the only description of how minimum thresholds were evaluated to avoid undesirable results appears to be the statements that “for the majority of the Subbasin, GSA representatives identified no undesirable results, even if groundwater were to reach historical low groundwater levels” and that no GSA indicated undesirable results would occur “if the minimum threshold was set deeper than the [historic low] based on their understanding.”24 The GSP provides no further explanation or description of how the individual GSAs concluded that there would be no undesirable results based on the minimum thresholds.

The GSP only considers an undesirable result to occur for groundwater levels in the Subbasin when at least 25 percent of representative monitoring wells (5 of 20 wells) fall below their minimum threshold value for two consecutive non-dry water years.25 The GSP does not justify or discuss how the GSAs developed the 25 percent threshold, nor does it explain or disclose the potential impacts anticipated during extended drier climate conditions using this threshold. In other words, the proposed management program may lead to potential effects on domestic wells or other beneficial uses and users during prolonged dry- or below-normal periods, and that information should, at a minimum, be disclosed and considered in the GSP. (See Potential Corrective Action 1d.) If, after considering this potential deficiency, the GSAs retain minimum thresholds that allow for continued lowering of groundwater levels, it is reasonable to assume that some 21 ESJ GSP, p. 253. 22 ESJ GSP, p. 254.
23 ESJ GSP, p. 258.
24 ESJ GSP, p. 255. 25 ESJ GSP, p. 253.

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groundwater well impacts (e.g., loss of production capacity) will occur during the implementation of the GSP. SGMA requires GSAs to consider the interests of all groundwater uses and users and to implement their GSPs to mitigate overdraft conditions.
26 Implementing specific projects and management actions prevents undesirable results and achieves the sustainable yield of the basin. The GSAs should describe how projects and management actions would address drinking water impacts due to continued overdraft between the start of GSP implementation and the achievement of the sustainability goal. If the GSP does not include projects or management actions to address drinking water impacts, the GSP should contain a thorough discussion, with supporting facts and rationale, explaining how and why GSAs determined not to include actions to address those impacts from continued groundwater lowering below pre-SGMA levels. (See Potential Corrective Action 1e.)
Additionally, related to the groundwater level declines allowed for by the GSA’s minimum thresholds, the GSAs have not explained how those groundwater level declines relate to the degradation of groundwater quality sustainability indicator. GSAs must describe, among other items, the relationship between minimum thresholds for a given sustainability indicator (in this case, chronic lowering of groundwater levels) and the other sustainability indicators.27 The GSAs generally commit to monitoring a wide range of water quality constituents but they have only developed sustainable management criteria for total dissolved solids because they state they have not observed a causal nexus between groundwater management and degradation associated with the other constituents. While Department staff are not aware of evidence sufficient to conclude that the GSAs acted unreasonably by focusing on total dissolved solids, it is clear that the GSAs did not consider, or at least did not document, the potential for degradation to occur due to further lowering of groundwater levels beyond the historic lows. (See Potential Corrective Action 1f.)
Potential Corrective Action 1
a) Department staff believe the management approach described in the GSP, which couples minimum thresholds and measurable objectives that account for operational flexibility during dry periods with a definition of undesirable results that disregards minimum threshold exceedances in all years except consecutive below normal, above normal, or wet years, to be inconsistent with the objectives of SGMA. Therefore, the GSAs should remove the water-year type requirement from the GSP’s undesirable result definition.
b) The GSP should be revised to include specific projects and management actions the GSAs would implement to offset drought-year groundwater level declines. c) The GSAs should thoroughly explain how their approach avoids undesirable results for subsidence and depletion of interconnected surface waters, as SGMA does not 26 23 CCR § 355.4(b)(4), 355.4(b)(6).
27 23 CCR § 354.28(b)(2).

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include an allowance or exemption for those conditions to continue in periods of drought.
d) Removing the water-year type requirement from the definition of an undesirable result (item a, above) would result in a GSP with groundwater level minimum thresholds designed to be generally protective of 90 percent of domestic wells regardless of regional hydrologic conditions. In that scenario, the GSAs should explain the rationale for determining that groundwater levels can exceed those thresholds at 25 percent of monitoring sites for two consecutive years before the effects would be considered significant and unreasonable. The GSAs should also explain how other factors they identified as "potential undesirable results" (e.g., adverse impacts to environmental uses and users) factored into selecting minimum thresholds and describe anticipated effects of the thresholds on beneficial uses and users of groundwater. Furthermore, the GSAs should explain whether other drinking water users that may rely on shallow wells, such as public water systems and state small water systems, were considered in the GSAs’ site-specific thresholds. If not, the GSAs should conduct outreach with those users and incorporate their shallow wells, as applicable, into the site-specific minimum thresholds and measurable objectives.
e) The GSAs should revise the GSP to describe how they would address drinking water impacts caused by continued overdraft during the period between the start of GSP implementation and achieving the sustainability goal. If the GSP does not include projects or management actions to address those impacts, the GSP should contain a thorough discussion, with supporting facts and rationale, explaining how and why the GSAs determined not to include specific actions to address drinking water impacts from continued groundwater lowering below pre-SGMA levels. f) The GSP should be revised to explain how the GSAs will assess groundwater quality degradation in areas where further groundwater level decline, below historic lows, is allowed via the minimum thresholds. The GSAs should further describe how they will coordinate with the appropriate groundwater users, including drinking water, environmental, and irrigation users as identified in the GSP. The GSAs should also discuss efforts to coordinate with water quality regulatory agencies and programs in the Subbasin to understand and develop a process for determining if continued lowering of groundwater levels is resulting in degraded water quality in the Subbasin during GSP implementation.

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Potential Deficiency 2. The GSP does not provide enough information to support the use of the chronic lowering of groundwater level sustainable management criteria and representative monitoring network as a proxy for land subsidence.

Background
The GSP Regulations state that minimum thresholds for land subsidence should identify the rate and extent of subsidence that substantially interferes with surface land uses and may lead to undesirable results. These quantitative values should be supported by: 28 • The identification of land uses or property interests potentially affected by land subsidence;
• An explanation of how impacts to those land uses or property interests were considered when establishing minimum thresholds;
• Maps or graphs showing the rates and extents of land subsidence defined by the minimum thresholds.

The GSP Regulations allow the use of groundwater elevations as a proxy for land subsidence. However, GSAs must demonstrate a significant correlation between groundwater levels and land subsidence and must demonstrate that groundwater level minimum thresholds represent a reasonable proxy for avoiding land subsidence undesirable results. Additionally, the GSAs must demonstrate how the monitoring network is adequate to identify undesirable results for both metrics.

Potential Deficiency Details
Department staff find that the GSP does not adequately identify or define minimum thresholds and undesirable results for land subsidence. The GSP also does not provide adequate justification and explanation for using the groundwater level minimum thresholds and representative monitoring network as a proxy for land subsidence.

Generally, the GSP identifies that irrecoverable loss of groundwater storage and damage to infrastructure, including water conveyance facilities and flood control facilities, are potential impacts of land subsidence.
29 However, the GSP does not identify specific
infrastructure locations, particularly those associated with public safety, in the Subbasin and the rate and extent of subsidence that would substantially interfere with those land surface uses and may lead to undesirable results. Additionally, without identifying infrastructure considered at risk for interference from land subsidence, Department staff cannot evaluate whether the groundwater level representative monitoring network is adequate to detect potential subsidence-related impacts.

Department staff find the GSP does not provide adequate evidence to demonstrate a significant correlation between groundwater levels and land subsidence in the Subbasin. 28 23 CCR § 354.28(c)(5). 29 ESJ GSP, p. 269.

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Without explaining this correlation, the Department cannot evaluate whether the groundwater level minimum thresholds and associated conditions required for identifying an undesirable result would protect against significant and unreasonable impacts related to land subsidence. The GSP states a significant correlation exists between groundwater levels and land subsidence, with lowering groundwater levels driving further land subsidence.30 Department staff agree with this general statement. However, the GSP fails to provide adequate evidence to evaluate further this correlation, specifically concerning potential subsidence caused by groundwater levels falling below historic lows, as would be allowed by the groundwater level minimum thresholds set in the GSP.

The GSP's justification for using the proposed groundwater level minimum thresholds as a proxy for land subsidence appears to rely mainly on an incomplete analysis and a data set with significant data gaps. The GSP states there are no historical records of significant and unreasonable land subsidence in the Subbasin.
31 The GSP also states that there is
a lack of direct land subsidence monitoring in the Subbasin.32 The GSP uses this absence of historical records to assert that historically dewatered geologic units are not compressible and, therefore, not at risk for land subsidence. Although groundwater level minimum thresholds are below historic lows, the GSP states that the GSAs do not expect further declines in groundwater levels to dewater materials deeper than 205 feet below ground surface (the deepest groundwater level minimum threshold value in the Subbasin).
33 The GSP states that subsurface materials encountered up to this depth are the same [non-compressible] geologic units that have been historically dewatered.

Department staff find multiple aspects of this justification speculative and not supported by the best available science. First, the GSP presents no analysis of historic groundwater levels or historically dewatered subsurface materials to support the conclusion that the geologic units are not compressible. Second, the GSP does not provide an evaluation showing how additional declines in groundwater levels would only affect subsurface materials similar to those which have been historically dewatered. Third, the GSP is unclear on whether the conditions required to identify an undesirable result for chronic lowering of groundwater levels in the Subbasin are also required to identify an undesirable result for land subsidence. Management proposed in the GSP could allow groundwater level minimum thresholds to be exceeded in periods where two consecutive non-dry years do not occur, which does not support the claim that only materials up to the deepest groundwater level minimum threshold (205 feet below ground surface) will be dewatered.

Department staff note that the legislature intended that implementation of SGMA would avoid or minimize subsidence34 once GSAs achieve the sustainability goal for a basin.

Without analysis examining how allowable groundwater levels below those historically 30 ESJ GSP, p. 270. 31 ESJ GSP, p. 269. 32 ESJ GSP, p. 270. 33 ESJ GSP, p. 270. 34 Water Code § 10720.1(e).

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Sustainable Groundwater Management Office Page 10 of 10 experienced in the Subbasin may affect land subsidence, Department staff cannot determine if the GSP adequately avoids or minimizes land subsidence. While SGMA does not require prevention of all land subsidence, the GSP does not provide sufficient evidence to conclude that the proposed chronic lowering of groundwater level minimum thresholds are adequate to detect and avoid land subsidence undesirable results.

Potential Corrective Action 2
The GSAs must provide detailed information to demonstrate how the use of the chronic lowering of groundwater level minimum thresholds are sufficient as a proxy to detect and avoid significant and unreasonable land subsidence that substantially interferes with surface land uses. Alternatively, the GSAs could commit to utilizing direct monitoring for subsidence, e.g., with remotely sensed subsidence data provided by the Department. In that case, the GSAs should develop sustainable management criteria based on rates and extents of subsidence. Department staff suggest the GSAs consider and address the following issues:

1. The GSAs should revise the GSP to identify the total subsidence that critical infrastructure in the Subbasin can tolerate during GSP implementation. Support this identification with information on the effects of subsidence on land surface beneficial uses and users and the amount of subsidence that would substantially interfere with those uses and users.

2. The GSAs should revise the GSP to document a significant correlation between groundwater levels and specific amounts or rates of land subsidence. The analysis should account for potential subsidence related to groundwater level declines below historical lows and further declines that are allowed to exceed minimum thresholds (i.e., during non-consecutive non-dry years, if applicable based on the resolution to Potential Deficiency 1, above). This analysis should demonstrate that groundwater level declines allowed during GSP implementation are preventative of the rates and magnitudes of land subsidence considered significant and unreasonable based on the identified infrastructure of concern. If there is not sufficient data to establish a correlation, the GSAs should consider other options such as direct monitoring of land subsidence (e.g., remotely sensed data provided by the Department, extensometers, or GPS stations) until such time that the GSAs can establish a correlation.

3. The GSAs should explain how the groundwater level representative monitoring network is sufficient to detect significant and unreasonable subsidence that may substantially interfere with land uses, specifically any identified infrastructure of concern. If the groundwater level monitoring network alone is not adequate, based on specific infrastructure locations, Department staff suggest incorporating continued analysis of available InSAR data to cover areas with data gaps.

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ATTACHMENT 2
2024
Groundwater Sustainability Plan Amendment
Complete Appendices November 2024
APPENDIX 3-B.

DETERMINATION LETTER FROM DWR TO ESJ ENTITLED
“APPROVED DETERMINATION OF THE REVISED

GROUNDWATER SUSTAINABILITY PLAN SUBMITTED FOR
THE SAN JOAQUIN VALLEY – EASTERN SAN JOAQUIN
SUBBASIN” DATED JULY 6, 2023
ATTACHMENT 2

CALIFORNIA DEPARTMENT OF WATER RESOURCES

SUSTAINABLE GROUNDWATER

MANAGEMENT OFFICE
715 P Street, 8th Floor | Sacramento, CA 95814 | P.O. Box 942836 | Sacramento, CA 94236-0001 STATE OF CALIFORNIA | GAVIN NEWSOM, GOVERNOR | CALIFORNIA NATURAL RESOURCES AGENCY July 6, 2023
Fritz Buchman
San Joaquin County Public Works
P.O. Box 1810
Stockton, CA 95201
[email protected]
RE: Approved Determination of the Revised Groundwater Sustainability Plan Submitted for the San Joaquin Valley – Eastern San Joaquin Subbasin Dear Fritz Buchman,
The Department of Water Resources (Department) has evaluated the resubmitted groundwater sustainability plan (GSP) for the San Joaquin Valley – Eastern San Joaquin Subbasin in response to the Department’s incomplete determination on January 28, 2022 and has determined the GSP is approved. The approval is based on recommendations from the Staff Report, included as an exhibit to the attached Statement of Findings, which describes that the groundwater sustainability agencies (GSAs) have taken sufficient action to correct deficiencies identified by the Department and the Eastern San Joaquin GSP satisfies the objectives of the Sustainable Groundwater Management Act (SGMA) and substantially complies with the GSP Regulations. The Staff Report also proposes recommended corrective actions that the Department believes will enhance the GSP and facilitate future evaluation by the Department. The Department strongly encourages the recommended corrective actions be given due consideration and suggests incorporating all resulting changes to the GSP in the future.

Recognizing SGMA sets a long-term horizon for GSAs to achieve their basin sustainability goals, monitoring progress is fundamental for successful implementation.

GSAs are required to evaluate their GSPs at least every five years and whenever the Plan is amended, and to provide a written assessment to the Department. Accordingly, the Department will evaluate approved GSPs and issue an assessment at least every five years. The Department will initiate the first periodic review of the Eastern San Joaquin GSP no later than January 29, 2025.

Please contact Sustainable Groundwater Management staff by emailing [email protected] if you have any questions related to the Department’s assessment or implementation of your GSP.

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STATE OF CALIFORNIA | GAVIN NEWSOM, GOVERNOR | CALIFORNIA NATURAL RESOURCES AGENCY Thank You,
________________________________
Paul Gosselin
Deputy Director
Sustainable Groundwater Management
Attachment:

1. Statement of Findings Regarding the Approval of the San Joaquin Valley – Eastern San Joaquin Groundwater Sustainability Plan (July 6, 2023) DocuSign Envelope ID: C2F2E88C-EC6C-4ABA-A79D-E13FB7954BF1 ATTACHMENT 2

Page 1 of 8 ends

STATE OF CALIFORNIA

DEPARTMENT OF WATER RESOURCES

STATEMENT OF FINDINGS REGARDING THE

APPROVAL OF THE
SAN JOAQUIN VALLEY – EASTERN SAN JOAQUIN SUBBASIN

GROUNDWATER SUSTAINABILITY PLAN
The Department of Water Resources (Department) is required to evaluate whether a submitted groundwater sustainability plan (GSP or Plan) conforms to specific requirements of the Sustainable Groundwater Management Act (SGMA or Act), is likely to achieve the sustainability goal for the basin covered by the Plan, and whether the Plan adversely affects the ability of an adjacent basin to implement its GSP or impedes achievement of sustainability goals in an adjacent basin. (Water Code § 10733.) The Department is directed to issue an assessment of the Plan within two years of its submission. (Water Code § 10733.4.) If a Plan is determined to be Incomplete, the Department identifies deficiencies that preclude approval of the Plan and identifies corrective actions required to make the Plan compliant with SGMA and the GSP Regulations. The GSA has up to 180 days from the date the Department issues its assessment to make the necessary corrections and submit a revised Plan. (23 CCR § 355.2(e)(2)). This Statement of Findings explains the Department’s decision regarding the revised Plan submitted by the Central Delta Water Agency GSA, Central San Joaquin Water Conservation District GSA, City of Lodi GSA, City of Manteca GSA, City of Stockton GSA, County of San Joaquin GSA - Eastern San Joaquin 1, County of San Joaquin GSA - Eastern San Joaquin 2, Eastside San Joaquin GSA, Linden County Water District GSA, Lockeford Community Service District GSA, North San Joaquin Water Conservation District GSA, Oakdale Irrigation District GSA, South Delta Water Agency GSA, South San Joaquin GSA, Stockton East Water District GSA, and Woodbridge Irrigation District GSA (GSAs or Agencies) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) (Basin No. 5-022.01).

Department management has discussed the Plan with staff and has reviewed the Department Staff Report, entitled Sustainable Groundwater Management Program Groundwater Sustainability Plan Assessment Staff Report, attached as Exhibit A, recommending approval of the GSP. Department management is satisfied that staff have conducted a thorough evaluation and assessment of the Plan and concurs with staff’s recommendation and all the recommended corrective actions. The Department therefore APPROVES the Plan and makes the following findings:

A. The initial Plan for the basin submitted by the GSA for the Department’s evaluation satisfied the required conditions as outlined in § 355.4(a) of the GSP Regulations (23 CCR § 350 et seq.), and Department Staff therefore evaluated the initial Plan.

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B. On January 28, 2022, the Department issued a Staff Report and Statement of Findings determining the initial GSP submitted by the Agencies for the Subbasin to be incomplete, because the GSP did not satisfy the requirements of SGMA, nor did it substantially comply with the GSP Regulations. At that time, the Department provided corrective actions in the Staff Report that were intended to address the deficiencies that precluded approval. Consistent with the GSP Regulations, the Department provided the Agencies with up to 180 days to address the deficiencies detailed in the Staff Report. On July 27, 2022, within the 180 days provided to remedy the deficiencies identified in the Staff Report related to the Department’s initial incomplete determination, the Agencies resubmitted a revised 2022 GSP to the Department for evaluation. When evaluating a revised GSP that was initially determined to be incomplete, the Department reviews the materials (e.g., revised or amended GSP) that were submitted within the 180-day deadline and does not review or rely on materials that were submitted to the Department by the GSA after the resubmission deadline. Part of the Department’s review focuses on how the Agencies have addressed the previously identified deficiencies that precluded approval of the initially submitted Plan. The Department shall find a Plan previously determined to be incomplete to be inadequate if, after consultation with the State Water Resources Control Board, the Department determines that the Agencies have not taken sufficient actions to correct the deficiencies previously identified by the Department. (23 CCR § 355.2(e)(3)(C).) The Department shall approve a Plan previously found to be incomplete if the Department determines the Agencies have sufficiently addressed the deficiencies that precluded approval. The Department may evaluate other components of the Plan, particularly to assess whether revisions to address deficiencies may have affected other components of a Plan or its likelihood of achieving sustainable groundwater management and may offer recommended corrective actions to deal with any issues of concern.

C. The Department’s Staff Report, dated January 28, 2022, identified the deficiencies that precluded approval of the initially submitted Plan. After thorough evaluation of the revised Plan, the Department makes the following findings regarding the sufficiency of the actions taken by the Agencies to correct those deficiencies:

1. Deficiency 1: The corrective action advised the Agencies to address several aspects of the Plan’s discussion, analyses, and justification of groundwater level, subsidence, and interconnected surface waters sustainable management criteria and potential impacts to beneficial uses and users. The Department found that the initial GSP did not adequately justify why undesirable results would only occur during consecutive non-dry water years for the chronic lowering of groundwater levels, land subsidence, and depletion of interconnected DocuSign Envelope ID: B2FBE303-033B-42A4-8D20-E59EEE13B174 ATTACHMENT 2
Statement of Findings July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources Page 3 of 8
surface water sustainability indicators. The Department also found that the GSP lacked sufficient explanation for the established minimum thresholds and undesirable results for groundwater levels.

The 2023 Staff Report associated with the revised Plan indicates that the Agencies have taken sufficient actions to correct this deficiency such that, at this time, although the Staff Report includes recommended corrective actions to further align this aspect of the Plan with the GSP Regulations, the Department no longer finds the deficiency to preclude approval, and further finds that the Agencies have the ability to achieve the sustainability goal for the basin on SGMA timelines, and that the Department will be able to periodically monitor and evaluate the likelihood of Plan implementation to achieve sustainability.

2. Deficiency 2: The corrective action advised the Agencies to address the Plan’s discussion supporting the use of chronic lowering of groundwater levels sustainable management criteria and monitoring network as a proxy for land subsidence. The initial GSP did not provide enough information supporting the use of groundwater levels as a proxy for subsidence.

The 2023 Staff Report indicates that the Agencies have taken sufficient actions to correct this deficiency such that, at this time, although the Staff Report includes recommended corrective actions to further align this aspect of the Plan with the GSP Regulations, the Department finds Plan approval is not precluded, that the Agencies have the ability to achieve the sustainability goal for the basin on SGMA timelines, and that the Department will be able to periodically monitor and evaluate the likelihood of Plan implementation to achieve sustainability.

D. The Plan satisfies the required conditions as outlined in § 355.4(a) of the GSP Regulations (23 CCR § 350 et seq.):

1. The Plan was complete, meaning it generally appeared to include the information required by the Act and the GSP Regulations sufficient to warrant a thorough evaluation and issuance of an assessment by the Department. (23 CCR § 355.4(a)(2).)

2. The Plan, either on its own or in coordination with other Plans, appears to cover the entire Basin sufficient to warrant a thorough evaluation. (23 CCR § 355.4(a)(3).)
E. The general standards the Department applied in its evaluation and assessment of the Plan are: (1) “conformance” with the specified statutory requirements, (2) DocuSign Envelope ID: B2FBE303-033B-42A4-8D20-E59EEE13B174 ATTACHMENT 2
Statement of Findings July 6, 2023
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“substantial compliance” with the GSP Regulations, (3) whether the Plan is likely to achieve the sustainability goal for the Subbasin within 20 years of the implementation of the Plan, and (4) whether the Plan adversely affects the ability of an adjacent basin to implement its GSP or impedes achievement of sustainability goals in an adjacent basin. (Water Code § 10733.) Application of these standards requires exercise of the Department’s expertise, judgment, and discretion when making its determination of whether a Plan should be deemed “approved,” “incomplete,” or “inadequate.”
The statutes and GSP Regulations require Plans to include and address a multitude and wide range of informational and technical components. The Department has observed a diverse array of approaches to addressing these technical and informational components being used by GSAs in different basins throughout the state. The Department does not apply a set formula or criterion that would require a particular outcome based on how a Plan addresses any one of SGMA’s numerous informational and technical components. The Department finds that affording flexibility and discretion to local GSAs is consistent with the standards identified above; the state policy that sustainable groundwater management is best achieved locally through the development, implementation, and updating of local plans and programs (Water Code § 113); and the Legislature’s express intent under SGMA that groundwater basins be managed through the actions of local governmental agencies to the greatest extent feasible, while minimizing state intervention to only when necessary to ensure that local agencies manage groundwater in a sustainable manner. (Water Code § 10720.1(h)). The Department’s final determination of a Plan’s status is made based on the entirety of the Plan’s contents on a case-by-case basis, considering and weighing factors relevant to the particular Plan and Subbasin under review.

F. In making these findings and Plan determination, the Department also recognized that: (1) it maintains continuing oversight and jurisdiction to ensure the Plan is adequately implemented; (2) the Legislature intended SGMA to be implemented over many years; (3) SGMA provides Plans 20 years of implementation to achieve the sustainability goal in a Subbasin (with the possibility that the Department may grant GSAs an additional five years upon request if the GSA has made satisfactory progress toward sustainability); and, (4) local agencies acting as GSAs are authorized, but not required, to address undesirable results that occurred prior to enactment of SGMA. (Water Code §§ 10721(r); 10727.2(b); 10733(a); 10733.8.)
G. The Plan conforms with Water Code §§ 10727.2 and 10727.4, substantially complies with 23 CCR § 355.4, and appears likely to achieve the sustainability goal for the Subbasin.

1. The sustainable management criteria and the GSP’s goal to maintain an economically viable groundwater resource for the beneficial use of the people of the Subbasin by operating within its sustainable yield or by modifying existing management actions to address future conditions are sufficiently justified and explained. The Plan relies on credible information and science to quantify the groundwater conditions that the Plan seeks to avoid and provides an objective way to determine whether the Basin is being managed sustainably in accordance with SGMA. (23 CCR § 355.4(b)(1).)

2. The Plan demonstrates a thorough understanding of where data gaps exist (e.g., hydrogeological conceptual model, groundwater conditions, and water budgets) and demonstrates a commitment to eliminate those data gaps. The GSP intends to address these data gaps by incorporating new information into the numerical model and expanding the existing monitoring network. Filling these known data gaps, and others described in the Plan, should lead to the refinement of the GSAs’ monitoring networks, the Subbasin’s water model, and sustainable management criteria to better inform and guide future adaptive management strategies. (23 CCR § 355.4(b)(2).)

3. The sustainable management criteria and projects and management actions are commensurate with the level of understanding of the Subbasin setting. The projects and management actions described in the Plan provide a feasible approach to achieving the Subbasin’s sustainability goal and should provide the GSAs’ with greater versatility to adapt and respond to changing conditions and future challenges during GSP implementation. (23 CCR § 355.4(b)(3).)

4. The Plan provides a detailed explanation of how the various interests of groundwater uses and users in the Subbasin were considered in developing the sustainable management criteria and how those interests would be impacted by the established minimum thresholds. (23 CCR § 355.4(b)(4).)

5. The Plan’s proposed projects and management actions appear feasible at this time and, if implemented expeditiously, appear likely to prevent undesirable results and ensure that the Subbasin is operated within its sustainable yield on SGMA timelines. The Department will continue to monitor Plan implementation and reserves the right to change its determination if projects and management actions are not implemented or appear unlikely to prevent undesirable results or unlikely to achieve sustainability within SGMA timeframes. (23 CCR § 355.4(b)(5).) DocuSign Envelope ID: B2FBE303-033B-42A4-8D20-E59EEE13B174 ATTACHMENT 2
Statement of Findings July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources Page 6 of 8

6. The Plan includes a reasonable assessment of overdraft conditions and includes reasonable means to mitigate overdraft, if present. (23 CCR § 355.4(b)(6).)

7. At this time, it does not appear that the Plan will adversely affect the ability of an adjacent basin to implement its GSP or impede achievement of sustainability goals in an adjacent basin. While no discussion was included on the potential impacts to adjacent basins, the Plan’s water budget included subsurface outflows and inflows estimates between the adjacent subbasins. The Plan states that various inter-basin coordination meetings have taken place with the seven adjacent subbasins mainly discussing the elements of the critically over-drafted Subbasin and efforts to coordinate in the future. (23 CCR § 355.4(b)(7).)

8. If required, a satisfactory coordination agreement has been adopted by all relevant parties. (23 CCR § 355.4(b)(8).)

9. The GSAs’ member agencies are Central Delta Water Agency, Central San Joaquin Water Conservation District, City of Lodi, City of Manteca, City of Stockton, Calaveras County Water District, Stanislaus County, Rock Creek Water District, Linden County Water District, Lockeford Community Services District, North San Water Conservation District, Oakdale Irrigation District, San Joaquin County, North Delta Water Agency, San Joaquin County No. 2 (Cal Water), South Delta Water Agency, South San Joaquin Irrigation District, City of Ripon, City of Escalon, Stockton East Water District, and Woodbridge Irrigation District.

Given the legal authority and financial resources of the GSAs’ member agencies and the additional authorities granted the GSAs’ under SGMA, the Department concludes the GSAs’ likely have the legal authority and financial resources necessary to implement the Plan. (23 CCR § 355.4(b)(9).)

10. Through review of the Plan and consideration of public comments, the Department determines that the GSAs adequately responded to comments that raised credible technical or policy issues with the Plan, sufficient to warrant approval of the Plan at this time. The Department also notes that the recommended corrective actions included in the Staff Report are important to addressing certain technical or policy issues that were raised and, if not addressed before future, subsequent plan evaluations, may preclude approval of the Plan in those future evaluations. (23 CCR § 355.4(b)(10).)
H. In addition to the grounds listed above, DWR also finds that:

1. The Plan provides an assessment conducted by the GSA which evaluated potential impacts to beneficial uses and users based on the established sustainable management criteria. The assessment estimated impacts to domestic and municipal supply wells by evaluating the 10th percentile well depths and comparing those to the initial minimum thresholds values to establish the minimum thresholds at individual representative monitoring points which, if not exceeded, would be protective of approximately 90-percent of domestic or municipal wells in the Subbasin. The Department developed its GSP Regulations consistent with and intending to further the human right to water policy (Water Code § 106.3) through implementation of SGMA and the Regulations, primarily by achieving sustainable groundwater management in a basin. By ensuring substantial compliance with the GSP Regulations, the Department has considered the state policy regarding the human right to water in its evaluation of the Plan. (23 CCR § 350.4(g).)

2. The Plan acknowledges and identifies interconnected surface waters within the Subbasin. The GSAs propose to use chronic groundwater level sustainable management criteria as proxy for the depletions of interconnected surface water sustainability indicator, however, the Department recognizes that many data gaps related to
interconnected surface water exist within the Subbasin. The GSAs should fill data gaps, evaluate additional modeling data, and coordinate with agencies and interested parties to understand beneficial uses and users that may be impacted by depletions of interconnected surface water caused by groundwater pumping.

Future updates to the Plan should aim to improve the sustainable management criteria as more information and improved
methodologies become available.

3. The California Environmental Quality Act (Public Resources Code § 21000 et seq.) does not apply to the Department’s evaluation and assessment of the Plan.

Accordingly, the revised GSP submitted by the Agencies for the Eastern San Joaquin Subbasin is hereby APPROVED. The recommended corrective actions identified in the Staff Report will assist the Department’s future review of the Plan’s implementation for consistency with SGMA and the Department therefore recommends the Agencies address them by the time of the Department’s periodic review, which is set to begin on January 29, 2025, as required by Water Code § 10733.8. Failure to address the Department’s Recommended Corrective Actions before future, subsequent plan evaluations, may lead to a Plan being determined incomplete or inadequate.

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Statement of Findings July 6, 2023
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Signed:
_________________________________
Karla Nemeth, Director
Date: July 6, 2023
Exhibit A: Groundwater Sustainability Plan Assessment Staff Report – San Joaquin Valley – Eastern San Joaquin Subbasin (July 6, 2023)
DocuSign Envelope ID: B2FBE303-033B-42A4-8D20-E59EEE13B174 ATTACHMENT 2
California Department of Water Resources
Sustainable Groundwater Management Program Page 1 of 53 State of California
Department of Water Resources
Sustainable Groundwater Management Program
Groundwater Sustainability Plan Assessment
Staff Report
Groundwater Basin Name: San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01)
Submitting Agencies: Central Delta Water Agency GSA; Central San Joaquin Water Conservation District GSA; City of Lodi GSA; City of Manteca GSA; City of Stockton GSA; County of San
Joaquin GSA - Eastern San Joaquin 1; County of San
Joaquin GSA - Eastern San Joaquin 2; Eastside San
Joaquin GSA; Linden County Water District GSA;
Lockeford Community Service District GSA; North San
Joaquin Water Conservation District GSA; Oakdale
Irrigation District GSA; South Delta Water Agency GSA;
South San Joaquin GSA; Stockton East Water District
GSA; Woodbridge Irrigation District GSA
Submittal Type: Revised Plan in Response to Incomplete Determination of the 2020 Groundwater Sustainability Plan
Submittal Date: July 27, 2022
Recommendation: Approve
Date: July 6, 2023
On July 27, 2022, the Central Delta Water Agency GSA, Central San Joaquin Water Conservation District GSA, City of Lodi GSA, City of Manteca GSA, City of Stockton GSA, County of San Joaquin GSA - Eastern San Joaquin 1, County of San Joaquin GSA - Eastern San Joaquin 2, Eastside San Joaquin GSA, Linden County Water District GSA, Lockeford Community Service District GSA, North San Joaquin Water Conservation District GSA, Oakdale Irrigation District GSA, South Delta Water Agency GSA, South San Joaquin GSA, Stockton East Water District GSA, and Woodbridge Irrigation District GSA (collectively, the GSAs or Agencies) submitted the Eastern San Joaquin Groundwater Subbasin Revised June 2022 Groundwater Sustainability Plan (GSP or Plan) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) to the Department of Water Resources (Department) in response to the Department’s incomplete determination on ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 2 of 53 January 28, 2022, 1 for evaluation and assessment as required by the Sustainable Groundwater Management Act (SGMA)2 and GSP Regulations.3 After evaluation and assessment, Department staff conclude the GSAs have taken sufficient actions to correct deficiencies identified by the Department and recommend approval of the 2022 Plan. Department staff have identified recommended corrective actions for the GSA to address by the Plan’s first periodic evaluation.

Overall, Department staff believe the Plan contains the required components of a GSP; demonstrates a thorough understanding of the Subbasin based on what appears to be the best available science and information; sets reasonable and supported sustainable management criteria to prevent undesirable results as defined in the Plan; has a reasonable monitoring network; and proposes a set of projects and management actions that, if successfully implemented, are likely to achieve the sustainability goal defined for the Subbasin.4 Department staff will continue to monitor and evaluate the Subbasin’s progress toward achieving the sustainability goal through annual reporting, periodic evaluations of the GSP, and GSP implementation.

This assessment includes six sections:
• Section 1 – Summary: Provides an overview of the Department’s assessment and recommendations.
• Section 2 – Evaluation Criteria: Describes the legislative requirements and the Department’s evaluation criteria.
• Section 3 – Required Conditions: Describes the submission requirements of a response to an incomplete determination to be evaluated by the Department. • Section 4 – Deficiency Evaluation: Provides an assessment of whether and how the contents included in the GSP resubmittal addressed the deficiencies identified by the Department in the initial incomplete determination. • Section 5 – Plan Evaluation: Provides a detailed assessment of the contents included in the GSP organized by each Subarticle outlined in the GSP Regulations. • Section 6 – Staff Recommendation: Includes the staff recommendation for the Plan and any recommended corrective actions.
1 Water Code § 10733.4(b); 23 CCR § 355.4(a)(4).
https://sgma.water.ca.gov/portal/service/gspdocument/download/7777. 2 Water Code § 10720 et seq. 3 23 CCR § 350 et seq. 4 23 CCR § 354.24.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 3 of 53 1 SUMMARY
Department staff conclude that the GSAs took sufficient action to correct the deficiencies previously identified. Accordingly, Department staff recommend approval of the Groundwater Sustainability Plan for the Eastern San Joaquin Groundwater Subbasin, along with implementation of corrective actions described in this Staff Report, which should be addressed by the next periodic Plan evaluation to further improve Plan implementation and achievement of basin sustainability in accordance with SGMA timelines.

The GSAs have identified areas for improvement of their Plan (e.g., addressing data gaps related to the hydrogeologic conceptual model and monitoring networks, including the refinement of aquifer characteristics, depth-discrete groundwater level and groundwater quality data, shallow groundwater levels near surface waters and natural communities commonly associated with groundwater (NCCAGs), and groundwater level data in the east and northwest areas of the Subbasin). Department staff concur that those items are important and recommend that the GSAs address them as soon as possible. Department staff have also identified additional recommended corrective actions designed to address shortcomings of the Plan, as described in this Staff Report, that the GSAs should consider for the first periodic evaluation of the Plan (see Section 6). The recommended corrective actions generally focus on the following:
1) groundwater level sustainable management criteria and the evaluation of impacts to beneficial uses and users,
2) land subsidence sustainable management criteria and monitoring network, 3) clarification of water budget and sustainable yield estimates, 4) clarification of sustainable management criteria related to the reduction of groundwater in storage,
5) additional explanation of seawater intrusion sustainable management criteria and the effects on beneficial uses and users, and clarification related to development the seawater intrusion isocontour line,
6) additional explanation of potential impacts related to depletions of interconnected surface waters, and additional details regard the existing and proposed monitoring network for depletions of interconnected surface water, 7) recommendations related to the seawater intrusion and groundwater quality monitoring networks.

Addressing the recommended corrective actions identified in Section 6 of this Staff Report will be important to demonstrate, on an ongoing basis, that implementation of the Plan is likely to achieve the sustainability goal.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 4 of 53 2 EVALUATION CRITERIA
The Department evaluates whether a Plan conforms to the statutory requirements of SGMA5 and is likely to achieve the basin’s sustainability goal,6 whether evaluating a basin’s first Plan,7 a Plan previously determined incomplete,8 an amended Plan,9 or a GSA’s periodic evaluation to an approved Plan.10 To achieve the sustainability goal, each version of the Plan must demonstrate that implementation will lead to sustainable groundwater management, which means the management and use of groundwater in a manner that can be maintained during the planning and implementation horizon without causing undesirable results. 11 The Department is also required to evaluate, on an ongoing basis, whether the Plan will adversely affect the ability of an adjacent basin to implement its groundwater sustainability program or achieve its sustainability goal.12 The Plan evaluated in this Staff Report is a revision of the 2020 Plan, which was evaluated by the Department and found to be incomplete. An incomplete Plan is one which Department staff identified one or more deficiencies that preclude its initial approval.

Deficiencies may include a lack of supporting information that is sufficiently detailed or analyses that are sufficiently thorough and reasonable, or where Department staff determine it is unlikely the GSA(s) in the basin/subbasin could achieve the sustainability goal under the proposed Plan. After GSAs have been afforded up to 180 days to address the deficiencies and based on the GSAs’ efforts, the Department can either approve13 the Plan or determine the Plan inadequate.
14 The Department’s evaluation and assessment of a revised or amended Plan, subsequent to the initial Plan being found to be incomplete, as presented in this Staff Report, continues to follow Article 6 of the GSP Regulations15 to determine whether the Plan, with revisions or additions prepared by the GSA, complies with SGMA and substantially complies with the GSP Regulations.16 As stated in the GSP Regulations, “substantial compliance means that the supporting information is sufficiently detailed and the analyses sufficiently thorough and reasonable, in the judgment of the Department, to evaluate the Plan, and the Department determines that any discrepancy would not materially affect the 5 Water Code §§ 10727.2, 10727.4, 10727.6.
6 Water Code § 10733; 23 CCR § 354.24. 7 Water Code § 10720.7. 8 23 CCR § 355.2(e)(2).
9 23 CCR § 355.10.
10 23 CCR § 355.6.
11 Water Code § 10721(v).
12 Water Code § 10733(c).
13 23 CCR §§ 355.2(e)(1).
14 23 CCR §§ 355.2(e)(3).
15 23 CCR § 355 et seq. 16 23 CCR § 350 et seq.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 5 of 53 ability of the Agency to achieve the sustainability goal for the basin, or the ability of the Department to evaluate the likelihood of the Plan to attain that goal.”17 When reviewing a revised or amended Plan that had previously been determined to be incomplete, Department staff primarily assess whether the GSA(s) have taken sufficient actions to correct any deficiencies identified by the Department.18 A Plan approval does not signify that Department staff, were they to exercise the professional judgment required to develop a Plan for the basin, would make the same assumptions and interpretations as those contained in the revised Plan, but simply that Department staff have determined that the modified assumptions and interpretations relied upon by the submitting GSA(s) are supported by adequate, credible evidence, and are scientifically reasonable.

Assessment of a revised or amended Plan previously determined to be incomplete may involve the review of new information presented by the GSA(s), including models and assumptions, and a reevaluation of that information based on scientific reasonableness.

In conducting its assessment, Department staff does not recalculate or reevaluate technical information or perform its own geologic or engineering analysis of that information.

The recommendation to approve a Plan previously determined to be incomplete is based on a determination that the GSA(s) have taken sufficient actions (e.g., amended or revised the Plan) to correct the deficiencies previously identified by the Department that precluded earlier approval.
3 REQUIRED CONDITIONS
For a Plan that the Department determines to be incomplete, the Department identifies corrective actions to address those deficiencies that preclude approval of the Plan as initially submitted. The GSAs in a basin, whether developing a single GSP covering the basin or multiple GSPs, must attempt to sufficiently address those corrective actions within the time provided, not to exceed 180 days, for the Plan to be evaluated by the Department.

3.1 INCOMPLETE RESUBMITTAL
The GSP Regulations specify that the Department shall evaluate a revised GSP if the GSA has taken corrective actions to address deficiencies within 180 days from the date the Department issued an incomplete determination.
19 The Department issued the incomplete determination on January 28, 2022. The GSAs submitted a revised GSP to the Department on July 27, 2022, within the 180-day deadline. 17 23 CCR § 355.4(b).
18 23 CCR §§ 355.2(e)(3)(C).
19 23 CCR § 355.4(a)(4).

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 6 of 53 4 DEFICIENCY EVALUATION
As stated in Section 355.4 of the GSP Regulations, a basin “shall be sustainably managed within 20 years of the applicable statutory deadline consistent with the objectives of the Act.” The Department’s assessment is based on a number of related factors including whether the elements of a GSP were developed in the manner required by the GSP Regulations, whether the GSP was developed using appropriate data and methodologies and whether its conclusions are scientifically reasonable, and whether the GSP, through the implementation of clearly defined and technically feasible projects and management actions, is likely to achieve a tenable sustainability goal for the basin.

In its initial incomplete determination, the Department identified deficiencies in the 2020 Plan which precluded that Plan’s approval.
20 In January 2022 the GSAs were given 180
days to take corrective actions to remedy the identified deficiencies. Consistent with the GSP Regulations, Department staff have evaluated the revised 2022 Plan to determine if the GSAs have taken sufficient actions to correct the deficiencies.

4.1 DEFICIENCY 1. THE GSP LACKS SUFFICIENT JUSTIFICATION FOR

DETERMINING THAT UNDESIRABLE RESULTS FOR CHRONIC LOWERING OF

GROUNDWATER LEVELS, SUBSIDENCE, AND DEPLETION OF INTERCONNECTED

SURFACE WATERS CAN ONLY OCCUR IN CONSECUTIVE NON-DRY WATER YEAR TYPES. THE GSP ALSO LACKS SUFFICIENT EXPLANATION FOR ITS MINIMUM

THRESHOLDS AND UNDESIRABLE RESULTS FOR CHRONIC LOWERING OF GROUNDWATER LEVELS.

4.1.1 Corrective Action
The corrective actions issued by the Department in its January 28, 2022, assessment related to this deficiency are as follows:

The GSAs must provide more detailed explanation and justification regarding the selection of the sustainable management criteria for groundwater levels, particularly the undesirable results and minimum thresholds, and the effects of those criteria on the interests of beneficial uses and users of groundwater. Department staff recommended the GSAs consider and address the following:
1a.Department staff believe the management approach described in the GSP, which couples minimum thresholds and measurable objectives that account for operational flexibility during dry periods with a definition of undesirable results that disregards minimum threshold exceedances in all years except consecutive below normal, above normal, or wet years, to be inconsistent with sustainable 20 https://sgma.water.ca.gov/portal/service/gspdocument/download/7777.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 7 of 53 groundwater management under SGMA. Therefore, the GSAs should remove the water-year type requirement from the GSP’s undesirable result definition. 1b.The GSP should be revised to include specific projects and management actions the GSAs would implement to offset drought-year groundwater level declines. 1c. The GSAs should thoroughly explain how their management approach and minimum thresholds avoid undesirable results for subsidence and depletion of interconnected surface waters, in light of the fact that SGMA does not include an allowance or exemption for conditions that occur during periods of drought for those sustainability indicators.
1d.Removing the water-year type requirement from the definition of an undesirable result (item a, above) would result in a GSP with groundwater level minimum thresholds designed to be generally protective of 90 percent of domestic wells regardless of regional hydrologic conditions. In that scenario, the GSAs should explain the rationale for determining that groundwater levels can exceed those thresholds at 25 percent of monitoring sites for two consecutive years before the effects would be considered significant and unreasonable. The GSAs should also explain how other factors they identified as "potential undesirable results" (e.g., adverse impacts to environmental uses and users) were considered when developing and selecting minimum thresholds and describe anticipated effects of the thresholds on beneficial uses and users of groundwater. Furthermore, the GSAs should explain whether other drinking water users that may rely on shallow wells, such as public water systems and state small water systems, were considered in the GSAs’ site-specific thresholds. If not, the GSAs should conduct outreach with those users and incorporate their shallow wells, as applicable, into the consideration of site-specific minimum thresholds and measurable objectives. 1e.The GSAs should revise the GSP to describe how they would address drinking water impacts caused by continued overdraft during the period between the start of GSP implementation and achieving the sustainability goal. If the GSP does not include projects or management actions to address those impacts, the GSP should contain a thorough discussion, with supporting facts and rationale, explaining how and why the GSAs determined not to include specific actions to address drinking water impacts from continued groundwater lowering below pre-SGMA levels. 1f. The GSP should be revised to explain how the GSAs will assess groundwater quality degradation in areas where further groundwater level decline, below historic lows, is allowed via the minimum thresholds. The GSAs should further describe how they will coordinate with the appropriate groundwater users, including drinking water, environmental, and irrigation users as identified in the GSP. The GSAs should also discuss efforts to coordinate with water quality regulatory agencies and programs in the Subbasin to understand and develop a process for determining if continued lowering of groundwater levels is resulting in degraded water quality ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 8 of 53 (e.g., increased concentrations of constituents of concern) in the Subbasin during GSP implementation.

4.1.2 Evaluation
In response to the multi-component corrective action provided for Deficiency 1, the Agencies submitted a revised GSP, including three new technical memoranda (Appendix 2-B, Appendix 3-D, and Appendix 3-E) address the deficiencies.

Deficiency 1a – relating to the exclusion of dry water year types in the identification of undesirable results for the chronic lowering of groundwater levels – was addressed in Appendix 2-B and Section 3.3.1.1.2 of the GSP.21 To address Deficiency 1a, the revised GSP changes the definition of an undesirable result for the chronic lowering of groundwater levels to remove the non-dry water year type requirement. This change results in an undesirable result for the chronic lowering of groundwater levels to be defined as “when at least 25 percent of representative monitoring wells used to monitor groundwater levels (5 of 20 wells in the Subbasin) fall below their minimum level thresholds for two consecutive years.”22 Department staff conclude this change to be sufficient to address Deficiency 1a.

Deficiency 1b – relating to the identification of projects and management actions that will offset drought-related groundwater level declines – was addressed in Appendix 2-B.

Deficiency 1b was initially recommended by Department staff as an alternative pathway to address the exclusion of dry and critical water year types in the identification of undesirable results for the chronic lowering of groundwater levels. With the removal of the water year type requirement, addressed in Deficiency 1a, Department staff believe that Deficiency 1b has already been addressed sufficiently; however, the GSP does provide an updated project list that includes potential surface water supplementation and in-lieu recharge estimates for different water year types and an updated modeling analysis of how projects will affect the groundwater budget and overdraft conditions in the Subbasin. The modeling results presented in the GSP indicate that even with the implementation of Category A Projects – defined as projects that are likely to advance in the next five years and have existing water rights or agreements – the Subbasin is projected to experience overdraft of 15,700 acre-feet per year when considering climate change.
23 The modeling results indicate that if Category A Projects are implemented as described, the Subbasin should not experience any undesirable results related to chronic lowering of groundwater levels (based on the updated definition), even under the climate change scenario; however, undesirable results may still occur (under the climate change scenario) if Category A Projects are not implemented as anticipated.24 Based on these results, the GSP acknowledges that additional projects and management actions may be needed to address projected overdraft under climate change, and potential undesirable 21 Eastern San Joaquin 2022 GSP, Appendix 2-B, pp. 1392-1393 and Section 3.3.1.1.2, p. 290. 22 Eastern San Joaquin 2022 GSP, Section 3.3.1.1.2, p. 290. 23 Eastern San Joaquin 2022 GSP, Appendix 2-B, p. 1402. 24 Eastern San Joaquin 2022 GSP, Appendix 2-B, p. 1408.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 9 of 53 results due to unforeseen changes in Category A Project implementation. The GSP indicates that an adaptive management approach will be utilized to address these concerns, and potential management actions and additional (Category B) projects were identified. 25 In general, Department staff conclude that the projects, potential management strategies and updated modeling results presented in the GSP provide a sufficient understanding of how the Agencies plan to manage the Subbasin under differing hydrologic conditions, even though the GSP acknowledges that additional, yet-to-be determined projects or management actions may be necessary to achieve sustainability.

Deficiency 1c, which requested additional justification to show how undesirable results for land subsidence and depletions of interconnected surface waters would not occur during dry water years where minimum thresholds are allowed to be exceeded (based on the previous definition of undesirable results and the use of groundwater levels as a proxy), was addressed sufficiently by the GSAs’ response to Deficiency 1a. With the removal of the water-year type requirement from the identification of undesirable results for the chronic lowering of groundwater levels, Deficiency 1c is also addressed.

Deficiency 1d was addressed in Appendix 3-D. In explaining the rationale for how undesirable results related to the chronic lowering of groundwater levels would only occur when at least 25 percent of representative monitoring wells exceed their minimum thresholds for two consecutive years, the GSP describes that the 25-percent threshold (of representative monitoring well exceedances) was considered to be sufficient to identify subbasin-wide undesirable results, whereas less than 25 percent would be considered more localized events. Additionally, the GSP explains that two consecutive years of exceedances were selected to identify an undesirable result because two years would establish a pattern rather than an isolated event, but three years of exceedances was felt to be too extreme. 26 While the rationale presented in the GSP is understandable, Department staff cannot determine whether it is reasonable as the GSP provides no additional analysis of these thresholds that would describe the potential allowable impacts. For example, while the GSP indicates that minimum thresholds are generally protective of 90 percent of domestic (or municipal) wells in the Subbasin, if groundwater levels in up to four of 20 representative monitoring wells are allowed to exceed minimum thresholds (without triggering undesirable results), then 90 percent of domestic (or municipal) wells are not truly protected. Updated modeling scenarios included in the GSP indicate that minimum threshold exceedances will still occur in some areas of the Subbasin.27 While Department staff do not believe this precludes approval at this time, they do believe that these modeling scenarios could be used to estimate potential impacts, particularly related to wells going dry, to support the notion that the proposed groundwater management approach will avoid significant and unreasonable undesirable results and recommend that minimum thresholds be evaluated in relation to the well depths of public water systems and state small water systems reliant on groundwater. 25 Eastern San Joaquin 2022 GSP, Appendix 2-B, pp. 1410-1412. 26 Eastern San Joaquin 2022 GSP, Appendix 3-D, p. 1595. 27 Eastern San Joaquin 2022 GSP, Appendix 2-B, pp. 1402-1409.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 10 of 53 While it may be reasonable to assume that wells in these systems are generally deeper than domestic wells, which were part of the minimum threshold analysis, Department staff recommend that an evaluation of these systems be disclosed by the GSP and an explanation for the selection of 25 percent exceedance for two years considered to be an undesirable result (see Recommended Corrective Action 1a).

Deficiency 1d also requested additional explanation for how other potential impacts, such as adverse impacts to environmental uses and users, were considered in the selection of minimum thresholds and the identification of undesirable results. In responding to this request, the Technical Memorandum included in Appendix 3-D essentially reiterated what was already presented in the original GSP. The revised GSP states that “[f]or the majority of the Subbasin, GSA representatives identified no undesirable results, even if groundwater were to reach historical low groundwater levels.”28 Additionally, while the explanation is somewhat unclear, the GSP implies that individual GSAs each “confirmed” that no undesirable results would occur if minimum thresholds were set deeper than historic lows (based on the established minimum thresholds). 29 The GSP does not disclose the potential impacts to environmental uses and users of groundwater related to the groundwater level minimum thresholds. Based on what is presented in the revised GSP, it is difficult for Department staff to evaluate the minimum thresholds and identification of undesirable results related to the chronic lowering of groundwater levels because no additional explanation or analysis was presented to describe how environmental uses and users would avoid experiencing significant and unreasonable impacts, particularly considering that groundwater level minimum thresholds are set below historic lows.

While it is understandable that the effects of changing groundwater levels on environmental uses and users may be difficult to observe and quantify than impacts that potentially affect groundwater wells or considered a data gap, the GSP does not present any analysis evaluating minimum thresholds in areas with identified GDEs. The GSP generally describes how the identification of GDEs will be further refined, and how new shallow monitoring wells will be constructed to collect additional data; however, there is no description for how this new data will be evaluated in conjunction with the minimum thresholds to evaluate impacts to environmental uses and users. While this does not preclude approval at this time, Department staff recommend the GSP include a more thorough evaluation of the impacts to environmental uses and users related to the groundwater level minimum thresholds, or, at minimum, provide a plan to evaluate impacts to environmental uses and users as additional data become available during GSP implementation (see Recommended Corrective Action 1b).

Additionally, Deficiency 1d requested explanation of how other groundwater users, such as public water systems and state small water systems, were considered in the development of minimum thresholds. In response to this request, the Technical 28 Eastern San Joaquin 2022 GSP, Appendix 3-D, p. 1598. 29 Eastern San Joaquin 2022 GSP, Appendix 3-D, p. 1598.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 11 of 53 Memorandum included in Appendix 3-D reiterated the domestic and municipal well analysis presented in the original GSP. 30 The GSP states that domestic wells are generally shallower than agricultural and municipal wells, which is why their analysis focuses on domestic wells. This analysis determined the 10th percentile of domestic well depth for all domestic wells (with data available in the Department’s Online System of Well Completion Reports [OSWCR] database) within a three-mile radius of each representative monitoring well (or two-mile radius for representative monitoring well 03N07E21L003 due to site-specific hydrogeologic conditions), and used this value as the minimum threshold (unless the historic low groundwater level plus buffer was shallower).

For areas served by municipal wells, a similar analysis was done based on nearby municipals wells. Department staff do not believe this analysis to be unreasonable; however, the deficiency specifically requested an explanation for how public water systems and small state water systems were considered.

Department staff suggest that a more detailed analysis of these smaller water systems be included in future GSP updates. The analysis should identify locations for public water systems and state small water systems in the Subbasin that rely on groundwater and evaluate whether minimum thresholds for nearby representative monitoring wells are sufficient to prevent significant and unreasonable impacts to these wells. While it may be assumed by GSAs that these small water systems are deeper than the 10th percentile domestic well depth and, thus, protected by the current minimum thresholds, Department staff would like evidence of this assumption disclosed in the Plan (see Recommended Corrective Action 1c).

Deficiency 1e identified the need for a description of drinking water impacts caused by continued overdraft during Plan implementation. This deficiency generally related to the continued overdraft and lowering of groundwater levels that would be allowed by the GSP in dry water years where minimum thresholds could be exceeded without triggering an undesirable result. The 2022 Plan addresses Deficiency 1e in Appendix 3-D. The information presented in Appendix 3-D indicates that the GSP plans to address long-term overdraft through the implementation of projects, but the GSP does not include any projects or management actions related to short-term impacts associated with drought.

The GSP indicates that existing water suppliers and the County Office of Emergency Services have programs or plans in place to address short-term drought-related emergency water supply issues, and that SGMA legislation does not require GSPs to include water supply contingency or dry well mitigation plans.31 The GSP also states that impacts to drinking water users were considered during the development of minimum thresholds, and with the removal of the water year type requirement, the established minimum thresholds will prevent a continued lowering of groundwater levels which should be sufficiently protective of most shallow domestic well users. The GSP indicates that an adaptive management approach will be utilized, and if impacts to drinking water users are 30 Eastern San Joaquin 2022 GSP, Appendix 3-D, pp. 1599-1600. 31 Eastern San Joaquin 2022 GSP, Appendix 3-D, pp. 1601-1603.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 12 of 53 identified during GSP implementation, minimum thresholds could be revised, or additional projects or management actions could be implemented.32 Department staff note that while the removal of the water year type requirement in the identification of undesirable results should lessen the chance for potential impacts to drinking water users, the minimum thresholds still allow for the lowering of groundwater levels below historic lows (ranging from 7.3 to 54.4 feet below historic low, depending on representative monitoring well site). Additionally, up to four of 20 representative monitoring wells are allowed to exceed these minimum thresholds without being considered an undesirable result, potentially resulting in undisclosed impacts to drinking water users across 20 percent of the Subbasin. Due to these factors, and as recommended previously under Recommended Corrective Action 1a, Department staff suggest that impacts to drinking water users (i.e., shallow domestic wells and small water systems) be evaluated using the updated modeling scenarios so that projected impacts under these scenarios can be used to guide future projects or management actions, if warranted.

Deficiency 1f requests that the GSP explain how groundwater quality degradation related to continued lowering of groundwater levels will be assessed. This deficiency was addressed in Technical Memorandum No. 3, included in Appendix 3-E. While the removal of the water year type requirement from the identification of undesirable results lessens the potential for continued lowering of groundwater levels Subbasin-wide, minimum thresholds still allow for groundwater levels to drop below historic lows. The GSP states that the only known correlation between groundwater quality and declining groundwater levels is related to the potential for saline water from the Delta to migrate inland when groundwater levels decline. The GSP states that “[t]hese sustainable management criteria were set specifically to help prevent the further migration of saline water.” 33 Department staff cannot identify where the GSP describes how the migration of saline water was evaluated in relation to the groundwater level minimum thresholds, as minimum thresholds were only described as being defined as the shallower of either the 10th percentile of domestic well depth, or the historic low groundwater level minus a buffer that represented the range of historic groundwater level fluctuations, as discussed above.

The GSP also states that “[aside from potential saline water migration] there is no evidence or historical data to indicate there is a relationship between lowering of groundwater levels and groundwater quality degradation.”34 While there may currently be no known correlation between groundwater levels and groundwater quality in the Subbasin, the GSP describes that groundwater quality results collected through GSP implementation, and also data from other water quality programs, will be evaluated in areas where groundwater level minimum thresholds are exceeded – and if groundwater quality secondary maximum contaminant levels (SMCLs) or minimum thresholds are also 32 Eastern San Joaquin 2022 GSP, Appendix 3-D, pp. 1602-1603. 33 Eastern San Joaquin 2022 GSP, Appendix 3-E, p. 1621. 34 Eastern San Joaquin 2022 GSP, Appendix 3-E, p. 1621.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 13 of 53 exceeded, the Agencies will convene a working group to assess whether groundwater management activities resulted in the groundwater quality exceedances.35 Department staff are encouraged by the commitment to evaluate groundwater quality data in areas where groundwater levels exceed minimum thresholds; however, the GSP presents little details on what the evaluation would entail. The GSP describes that groundwater quality degradation related to groundwater level declines will be evaluated in areas where groundwater levels fall below minimum thresholds. Considering that none of the representative monitoring wells in the groundwater level network are also sampled for groundwater quality (as part of the described GSP monitoring efforts), it is unclear how groundwater level declines observed in these wells will be correlated with changing groundwater quality conditions, particularly if no evaluation will be conducted until minimum thresholds are exceeded. In order to evaluate the changes in groundwater quality, sufficient groundwater quality data in the vicinity of the representative monitoring wells must be collected prior to the groundwater level declines occurring. Department staff recommend that as GSP implementation continues, the Agencies develop a more detailed plan describing how this assessment will be conducted, including identifying specific analyses, well locations (either wells already monitored as part of GSP implementation or wells monitored by other programs), sampling frequency, and data gaps (see Recommended Corrective Action 1d).

Deficiency 1f also requests additional information for how the Agencies plan to coordinate with groundwater users regarding groundwater quality degradation, and for how the Agencies plan to coordinate with other regulatory agencies or programs to develop a process to evaluate the effect of declining groundwater levels on groundwater quality in the Subbasin. The GSP provides a summary of how groundwater users will generally be involved or communicated with, including through stakeholder outreach and engagement efforts, a website, a future database management system, and the annual reporting.36 Regarding coordination with other groundwater quality programs, the revised GSP provides additional management actions to enhance the coordination and evaluation of groundwater quality results among the different programs in the Subbasin. 37 These management actions include establishing a process for regular coordination by having an annual meeting or workshop with other water quality programs and inviting Water Board staff to participate in regular Technical Advisory Committee meetings; developing monitoring data sharing agreements; including water quality data from external programs in the Subbasin’s data management system and evaluating these data with groundwater levels to identify whether a correlation exists; and including water quality data from other programs in the annual reporting. Department staff believe these coordination efforts described by the GSP to be sufficient.
35 Eastern San Joaquin 2022 GSP, Appendix 3-E, p. 1623. 36 Eastern San Joaquin 2022 GSP, Appendix 3-E, pp. 1623-1624. 37 Eastern San Joaquin 2022 GSP, Appendix 3-E, pp. 1625-1626.

4.1.3 Conclusion
Overall, Department staff believe the GSAs have taken sufficient action to correct Deficiency 1 by removing the water year type requirement from the definition of undesirable results for the chronic lowering of groundwater levels, further describing the undesirable results, providing updated modeling analyses, and describing new management actions, as described above and in the revised GSP. However, Department staff have identified four recommended corrective actions related to Deficiency 1 that do not preclude approval at this time but would further improve the GSP. GSAs should consider addressing Recommended Corrective Actions 1a through 1d, described below, by the next periodic evaluation.

4.2 DEFICIENCY 2. THE GSP DOES NOT PROVIDE ENOUGH INFORMATION TO

SUPPORT THE USE OF THE CHRONIC LOWERING OF GROUNDWATER LEVEL

SUSTAINABLE MANAGEMENT CRITERIA AND REPRESENTATIVE MONITORING NETWORK AS A PROXY FOR LAND SUBSIDENCE.

4.2.1 Corrective Action
The corrective actions issued by the Department in its January 28, 2022, assessment related to this deficiency are as follows:

The GSAs must provide detailed information to demonstrate how the use of the chronic lowering of groundwater level minimum thresholds are sufficient as a proxy to detect and avoid significant and unreasonable land subsidence that substantially interferes with surface land uses. Alternatively, the GSAs could commit to utilizing direct monitoring for subsidence, e.g., with remotely sensed subsidence data provided by the Department. In that case, the GSAs should develop sustainable management criteria based on rates and extents of subsidence. Department staff suggest the GSAs consider and address the following issues:
2a.The GSAs should revise the GSP to identify the total extent and rates of subsidence that critical infrastructure in the Subbasin can tolerate during GSP implementation. Support this identification with information on the effects of subsidence on land surface beneficial uses and users and the amount of subsidence that would substantially interfere with those uses and users. 2b.The GSAs should revise the GSP to document a significant correlation between groundwater levels and specific amounts or rates of land subsidence. The analysis should account for potential subsidence related to groundwater level declines below historical lows and further declines that would exceed minimum threshold levels (i.e., during non-consecutive non-dry years, if applicable based on the resolution to Deficiency 1, above). This analysis should demonstrate that groundwater level declines allowed during GSP implementation are preventative of the rates and extent of land subsidence considered significant and unreasonable based on the identified infrastructure of concern. If there is not sufficient data to ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 15 of 53 establish a correlation, the GSAs should consider other options such as direct monitoring of land subsidence (e.g., remotely sensed data provided by the Department, extensometers, GPS stations, etc.) until such time that the GSAs can establish a correlation.
2c. The GSAs should explain how the groundwater level representative monitoring network is sufficient to detect significant and unreasonable rates or extents of subsidence that may substantially interfere with land uses, specifically any identified infrastructure of concern. If the groundwater level monitoring network alone is not adequate, based on specific infrastructure locations, Department staff suggest incorporating continued analysis of available InSAR [Interferometric Synthetic Aperture Radar] data to cover areas with data gaps.

4.2.2 Evaluation
Deficiency 2 was addressed in Technical Memorandum No. 4, included in the GSP as Appendix 3-F.38 The Technical Memorandum provides additional information related to land subsidence in the Subbasin, including expanded discussions of critical infrastructure that would at risk due to land subsidence and the correlation between groundwater levels and land subsidence. Additionally, the Technical Memorandum proposes new management actions related to the monitoring of land subsidence in the Subbasin.

Deficiency 2a requests that the GSP describe the rate and extent of subsidence that would be considered significant and unreasonable, with respect to infrastructure of concern identified in the Subbasin. The revised GSP provides a general discussion of critical infrastructure types but does not identify specific infrastructure, stating “due to the sensitive nature of the critical infrastructure, specific infrastructure are not named.”39 The GSP does not define specific rates or extents of subsidence that would potentially impact this infrastructure or be considered significant and unreasonable. Regarding the evaluation of land subsidence in relation to critical infrastructure, the GSP only states that “[t]hrough input from OES, the critical infrastructure in the Subbasin can generally tolerate a significant amount of uniform settlement due to subsidence across the Subbasin, though the total amount of settlement that can be tolerated is dependent on the design of the specific infrastructure. Differential settlement across facilities in a locale, on the other hand, will result in more damage.”40 While this does not preclude approval at this time, based on the information provided, Department Staff believe additional information is needed to address Deficiency 2a, as the GSP does not provide a numerical rate and extent of land subsidence that would be associated with significant and unreasonable impacts Subbasin-wide. Department staff have provided an explanation in the conclusion (see Conclusion and Recommended Corrective Action 2).
38 Eastern San Joaquin 2022 GSP, Appendix 3-F, pp. 1629-1656. 39 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1631. 40 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1632.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 16 of 53 Deficiency 2b requests that the GSP be revised to describe the correlation between groundwater levels and land subsidence, to show that the use of groundwater level minimum thresholds as a proxy for land subsidence are protective of the rates and extents of land subsidence considered significant and unreasonable. The GSP reiterates what was presented in the original GSP, stating that “there are no historical records of impacts from land subsidence in the Eastern San Joaquin Subbasin.” Additionally, the GSP implies that minimum thresholds for groundwater levels will only allow for the dewatering of geologic units similar to those dewatered historically, which have shown no signs of subsidence historically.41 Finally, the GSP describes that compressible clays that are prone to subsidence are “not known to be common” in the Subbasin, with the exception of the Corcoran Clay being present in a small are in the southwest corner of the Subbasin.42 In this area of the Subbasin the top of the Corcoran Clay unit is located at an elevation of approximately -176 feet mean sea level (ft msl). The GSP states that the minimum threshold for representative monitoring well 02S07E31N001M in this area is set well above Corcoran Clay depth, at 1.5 ft msl; however, the GSP has also established a separate groundwater level trigger in this area of -150 ft msl, which is intended to alert the Agencies when the potential for subsidence would become a concern, prior to dewatering the Corcoran Clay.43
The GSP indicates that groundwater level minimum thresholds will still be used as a proxy for land subsidence; however, the GSP does not clarify what constitutes an undesirable result for land subsidence. Assuming an undesirable result for land subsidence is defined similarly to that for the chronic lowering of groundwater levels, Department staff recognize that with the removal of the water year type exclusion, the potential for continued Subbasin-wide groundwater level declines below the established minimum thresholds is lessened. However, because groundwater level minimum thresholds can be exceeded in up to four of 20 representative monitoring wells without being considered an indicator of potential undesirable results in the basin, there is the potential to dewater deep geologic units below minimum thresholds which were not evaluated in the GSP with regard to land subsidence. The GSP indicates that the correlation between groundwater levels and land subsidence will be further evaluated during GSP implementation by incorporating data such as continuous global positioning system (CGPS) data, and InSAR data, airborne electromagnetic data, as available, and that the representative monitoring well network or subsidence monitoring methods will be updated as needed.44 While not precluding approval at this time, Department staff believe that the GSP does not provide sufficient evidence to support the use of groundwater levels as a proxy for land subsidence and have provided an explanation and recommended corrective action in the conclusion (see Conclusion and Recommended Corrective Action 2).
41 Eastern San Joaquin 2022 GSP, Section 3.3.5.2, p. 313. 42 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1633. 43 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1633. 44 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1634.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 17 of 53 Deficiency 2c asks that the GSP describe how the existing groundwater monitoring network is sufficient to detect significant and unreasonable land subsidence in relation to the identified infrastructure of concern. The revised GSP does not attempt to describe how the existing groundwater monitoring network is sufficient; rather, the GSP commits to evaluating other forms of land subsidence monitoring data, such as CGPS and InSAR data. The revised GSP also establishes a trigger value of 0.25 feet of annual land subsidence (based on available InSAR or CGPS data) which will initiate further evaluation to determine whether the subsidence is the result of groundwater management activities.

Department staff note that the evaluation process related to determining the effect of groundwater management on subsidence is not described, though the GSP states that the results of the evaluation could potentially lead to additional projects or management actions.45 Department staff believe that the GSP’s incorporation of InSAR data to monitor for land subsidence is a step in the right direction but has provided a recommended corrective action in the conclusion (see Conclusion and Recommended Corrective Action 2).

4.2.3 Conclusion
Due to the lack of historical land subsidence in the Subbasin, and the likely minimal risk for land subsidence in the near-term, Department staff conclude that by adding the evaluation of direct subsidence monitoring data and annual trigger value of 0.25 feet, the Agencies’ response to Deficiency 2 is sufficient at this time and does not preclude approval. However, Department staff also believe that the use of groundwater levels as a proxy for land subsidence sustainable management criteria and the use of the representative groundwater level monitoring network to identify undesirable results related to land subsidence to be poorly supported based on the information presented in the GSP. Department staff recommend the use of InSAR data for the land subsidence monitoring network, with supplemental groundwater level data being utilized to evaluate whether detected land subsidence is the result of declining groundwater levels and believe this should be addressed by the first periodic evaluation. 45 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1642.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 18 of 53 5 PLAN EVALUATION
As stated in Section 355.4 of the GSP Regulations, a basin “shall be sustainably managed within 20 years of the applicable statutory deadline consistent with the objectives of the Act.” The Department’s assessment is based on a number of related factors including whether the elements of a GSP were developed in the manner required by the GSP Regulations, whether the GSP was developed using appropriate data and methodologies and whether its conclusions are scientifically reasonable, and whether the GSP, through the implementation of clearly defined and technically feasible projects and management actions, is likely to achieve a tenable sustainability goal for the basin.

The Department staff’s evaluation of the likelihood of the Plan to attain the sustainability goal for the Basin is provided below. Department staff consider the information presented in the Plan to satisfy the general requirements of the GSP Regulations.

5.1 ADMINISTRATIVE INFORMATION
The GSP Regulations require each Plan to include administrative information identifying the submitting Agency, describing the plan area, and demonstrating the legal authority and ability of the submitting Agency to develop and implement a Plan for that area.46 The GSP was developed by the Eastern San Joaquin Groundwater Authority (ESJGWA), a joint powers authority comprised of 16 individual GSAs in the Subbasin. Each GSA has two appointed representatives on the ESJGWA Board of Directors (Board) - one Board member and one alternate member. The GSP describes that GSP implementation will be conducted though the ESJGWA as the coordinating agency, and that the GSP covers the entire geographic extent of the Subbasin. Decisions regarding Subbasin-wide GSP implementation are generally approved by a majority vote of the 16 Board members; however, a two-thirds supermajority is needed for certain items such as approval of the annual budget, levying of taxes or fees, decisions on curtailment of pumping, and adoption of new rules that govern the ESJGWA.47 The GSP provides a brief description of each GSA, and also describes the legal authorities of the GSAs and the ESJGWA.48 In addition to the ESJGWA Board, the GSP describes that an Advisory Committee, made up of one member from each GSA, provides guidance to the Board regarding development of the GSP including groundwater conditions, sustainable management criteria, and projects and management actions.49 The Subbasin also has a Groundwater Sustainability Workgroup (Workgroup) which also provides input to the Board. The 46 23 CCR § 354.2 et seq. 47 Eastern San Joaquin 2022 GSP, Section 1.1.4.2, pp. 43-44. 48 Eastern San Joaquin 2022 GSP, Section 1.1.4.3, pp. 44-48 and Section 1.1.4.4, p. 48. 49 Eastern San Joaquin 2022 GSP, Section 1.1.4.2, p. 43.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 19 of 53 Workgroup is described by the GSP as being comprised of 23 community members that represent a diverse range of stakeholders in the community.50 The GSP describes that the Subbasin encompasses approximately 1,195 square miles and is part of the larger San Joaquin Valley Groundwater Basin. The GSP states that the Plan Area covers the entire Subbasin. The Subbasin is generally bound by Dry Creek on the north, the San Joaquin River on the west, the crystalline bedrock of the Sierra Nevada foothills on the east, and either the San Joaquin County line or the Stanislaus River on the south.51 Adjacent subbasins include the Consumnes, Solano, and South American to the north, East Contra Costa and Tracy to the west, and the Delta Mendota and Modesto to the south. A map showing the Subbasin and adjacent subbasins is shown in Figure 1 below.

Figure 1. Eastern San Joaquin Subbasin Location Map
The GSP provides various figures displaying jurisdictional boundaries in the Subbasin, including GSAs, Cities, Counties, Federal and State lands, and disadvantaged communities (DACs). The GSP also includes maps and descriptions of land use characteristics including general land use types, crop types, and well density maps for 50 Eastern San Joaquin 2022 GSP, Section 1.1.4.2, pp. 43-44. 51 Eastern San Joaquin 2022 GSP, Section 1.2.1.1, pp. 49-53.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 20 of 53 domestic, agricultural, and public wells.
52 The GSP describes that the majority of land use
in the Subbasin is for agriculture, with the dominant crop types being fruit and nut trees and vine crops.53
The GSP lists the general categories of the beneficial uses and users of groundwater in the Subbasin as being consistent with those identified in Water Code §10723.2. Of these general categories, the GSP identifies specific local agencies, DACs, and community water systems that are considered beneficial users in the Subbasin.54 Environmental users, such as groundwater dependent ecosystems (GDEs) and freshwater species reliant on instream flows are also identified (where data was available). 55 The GSP provides a list of public meetings held during GSP development to obtain input from stakeholders and the community, and also describes additional outreach efforts, such as a website, a stakeholder database, a situation assessment conducted through the Department Facilitation Support Services, and a Stakeholder Outreach and Engagement Plan.56 Additionally, the GSP describes that the draft GSP was available for a 45-day public comment period (prior to submission to the Department). Public comments received for the GSP and responses to those comments are included as appendices. 57 The GSP’s discussion and presentation of administrative information covers the specific items listed in the GSP Regulations in an understandable format using appropriate data.

Staff are aware of no significant inconsistencies or contrary information to that presented in the GSP and therefore have no significant concerns regarding the quality, data, and discussion of this subject in the GSP. The administrative information included in the Plan substantially complies with the requirements outlined in the GSP Regulations.

5.2 BASIN SETTING
GSP Regulations require information about the physical setting and characteristics of the basin and current conditions of the basin, including a hydrogeologic conceptual model; a description of historical and current groundwater conditions; and a water budget accounting for total annual volume of groundwater and surface water entering and leaving the basin, including historical, current, and projected water budget conditions.58

5.2.1 Hydrogeologic Conceptual Model
The GSP Regulations require a descriptive hydrogeologic conceptual model of the basin that includes a written description supported by cross sections and maps. 59 The hydrogeologic conceptual model is a non-numerical model of the physical setting, 52 Eastern San Joaquin 2022 GSP, Section 1.2.1.1, pp. 52-61. 53 Eastern San Joaquin 2022 GSP, Section 1.2.1.1, p. 55. 54 Eastern San Joaquin 2022 GSP, Section 1.3.1, pp. 80-81 and Appendix 1-F, pp. 534-548. 55 Eastern San Joaquin 2022 GSP, Section 1.3.1, pp. 80, Figure 2-73, p. 209, Appendix 1-G, pp. 550-569. 56 Eastern San Joaquin 2022 GSP, Section 1.3, pp. 81-92. 57 Eastern San Joaquin 2022 GSP, Appendix 1-I, pp. 588-944 and Appendix 1-J, pp. 946-992. 58 23 CCR § 354.12 et seq. 59 23 CCR § 354.12 et seq.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 21 of 53 characteristics, and processes that govern groundwater occurrence within a basin, and represents a GSA’s understanding of the geology and hydrology of the basin that support the geologic assumptions used in developing mathematical models, such as those that allow for quantification of the water budget.60
The hydrogeologic conceptual model presented in the GSP describes the physical components of the Subbasin and provides a general understanding for how the components relate to the groundwater system and the interaction between surface water and groundwater. The GSP provides maps and descriptions of surficial features including topography, major surface water features, watersheds, soil types, depositional environments, and recharge and discharge areas.61 The GSP indicates that the Subbasin does not rely on imported surface water and that water for the Subbasin is supplied by either groundwater or local surface water.
62 The GSP describes the regional and local
geologic setting, with supporting figures such as a block diagram, geologic map, and five geologic cross-sections. Geologic formations underlying the Subbasin are also identified and described.63
The GSP describes that the Subbasin is part of the larger San Joaquin Valley groundwater basin and the lateral boundaries of the Subbasin generally consist of the crystalline bedrock of the Sierra Nevada foothills to the east, Dry Creek to the north, the Mokelumne River to the northwest, the San Joaquin River to the west, and the Stanislaus River to the south.64 The bottom of the Subbasin is defined as the base of freshwater, which represents the approximate maximum extent of non-saline freshwater beneath the Subbasin. The base of freshwater in the Subbasin varies from approximately 650 to 2,000 feet below ground surface.65 The GSP identifies three major structural features in the Subbasin: the Stockton Fault, the Vernalis Fault, and the Stockton Arch. The GSP does not indicate whether these structures have any effect on the flow of groundwater; however, based on when they are estimated to have occurred, it appears that the freshwater bearing units were generally deposited during later time periods. 66 The GSP identifies one principal aquifer that provides groundwater for domestic, agricultural, and municipal supply. 67 The GSP indicates that there are no regionally extensive aquitards in the Subbasin, except for a small area in the southwest portion of 60 Department of Water Resources Best Management Practices for the Sustainable Management of Groundwater: Hydrogeologic Conceptual Model, December 2016: https://water.ca.gov/-/media/DWRWebsite/Web-Pages/Programs/Groundwater-Management/Sustainable-Groundwater-Management/BestManagement-Practices-and-Guidance-Documents/Files/BMP-3-Hydrogeologic-ConceptualModel_ay_19.pdf. 61 Eastern San Joaquin 2022 GSP, Section 2.1.4, pp. 109-123. 62 Eastern San Joaquin 2022 GSP, Section 2.1.4.4, p. 119. 63 Eastern San Joaquin 2022 GSP, Section 2.1.2, p. 108, Section 2.1.3, p. 109, Section 2.1.5, pp. 123-130, Section 2.1.7, pp. 134-139. 64 Eastern San Joaquin 2022 GSP, Section 2.1.8, pp. 141-142. 65 Eastern San Joaquin 2022 GSP, Section 2.1.8.2, p. 142. 66 Eastern San Joaquin 2022 GSP, Section 2.1.6, p. 131. 67 Eastern San Joaquin 2022 GSP, Section 2.1.9, p. 142.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 22 of 53 the Subbasin that contains the Corcoran Clay. The GSP describes that, in general, the principal aquifer is comprised of laterally extensive and interbedded layers of high and low permeability deposits, and there is evidence to support a hydraulic connection for the entire vertical extent of the aquifer.68 While only one principal aquifer was defined, the GSP differentiates between shallow, intermediate, and deep water-bearing zones. The shallow zone is comprised of recent alluvium, the Modesto formation, the Riverbank formation, and the upper unit of the Turlock Lake formation. The intermediate zone is comprised of the lower unit of the Turlock Lake formation and the Laguna formation. The deep zone consists of the Mehrten formation. Depths and thicknesses of the geologic formations (and associated aquifer zones) can be visualized on the provided cross sections. The GSP presents estimates of transmissivity, specific yield or storage coefficient, and vertical permeability for each water-bearing zone.69 Regarding data gaps and uncertainties associated with the hydrogeological conceptual model, the GSP identified the following: aquifer characteristics (such as hydraulic conductivity, transmissivity, and storage parameters); depth-specific groundwater level data; shallow groundwater level data near surface waters and NCCAGs; groundwater level data in the east and northwest areas of the Subbasin; groundwater level data near major creeks, rivers, and subbasin boundaries to evaluate subsurface flow and groundwater-surface water interaction; depth-specific groundwater quality data, the effect of the Stockton Fault on base of freshwater; and characterization of soil conditions related to recharge.
70 While these data gaps related to the hydrogeologic conceptual model are identified, the GSP provides little details on addressing some of the identified data gaps.

The proposed plans to fill data gaps mainly focus on collecting additional groundwater level and groundwater quality data from existing or newly constructed wells during the implementation period and updating or refining the numerical model; 71 however, the GSP
does not describe plans for addressing data gaps related to aquifer parameters, soil recharge areas, or the effects of the Stockton Fault on groundwater conditions.

While the GSP does not provide plans to address every data gap identified, overall, the information provided in the GSP that comprises the hydrogeologic conceptual model substantially complies with the requirements outlined in the GSP Regulations. In general, the Plan’s descriptions of the regional geologic setting, the Subbasin’s physical characteristics, the principal aquifer, and hydrogeologic conceptual model appear to utilize the best available science. Department staff are aware of no significant inconsistencies or contrary technical information to that presented in the Plan. 68 Eastern San Joaquin 2022 GSP, Section 2.1.9.1.4, p. 146. 69 Eastern San Joaquin 2022 GSP, Section 2.1.9.1, pp. 142-145. 70 Eastern San Joaquin 2022 GSP, Section 2.1.10, pp. 159-160. 71 Eastern San Joaquin 2022 GSP, Section 4.7.5, pp. 330-332.

5.2.2 Groundwater Conditions
The GSP Regulations require a written description of historical and current groundwater conditions for each of the six sustainability indicators and GDEs. 72 The GSP provides a description of current and historical groundwater level conditions in the Subbasin, and presents supporting documentation in the form of hydrographs, contour maps, and references to historical reports. The GSP describes that, in general, groundwater levels in the Subbasin have shown declining trends throughout much of their period of record. The GSP presents a figure that displays ten hydrographs with at least 40 years of historical data located throughout the Subbasin. 73 Based on the figure, groundwater levels across the Subbasin have generally displayed steady groundwater level declines, with major fluctuations (increases and decreases) generally corresponding to prolonged or extreme wet or dry periods, such as the 1982 to 1984 wet and above normal water years or early 1990s drought period. The GSP describes that, based on information from historical reports, the Subbasin historically had a westerly groundwater flow direction that parallels topography; however, groundwater elevation maps from the 1950s and 1960s displayed a groundwater depression near the City of Stockton that resulted in groundwater flowing east toward the City of Stockton from the Delta.74 The GSP presents groundwater elevation contour maps based on first quarter 2017 and fourth quarter 2017 data to display current groundwater conditions.75 Based on these figures, there is currently a large groundwater depression in the middle of the Subbasin, east of the City of Stockton. The GSP notes that this depression is “most significant to achieving sustainability in the Subbasin” (as compared to the groundwater depression in the north originating in the adjacent Consumnes Subbasin). Due to this central groundwater depression, current groundwater flow conditions are generally from the outer edges of the Subbasin towards the center.76
Groundwater storage conditions in the Subbasin were estimated using the Eastern San Joaquin Water Resources Model (ESJWRM), which is a numerical model for the Eastern San Joaquin Subbasin based on the Department’s Integrated Water Flow Model (IWFM). 77 The GSP describes that historical changes in groundwater storage were estimated from 1996 to 2015, with a total cumulative change in storage of -0.91 million acre-feet (MAF) during that time period, and an average annual change in storage of -

0.05 MAF. Current (2015) fresh (non-saline) groundwater in storage for the Subbasin is estimated to be 53.0 MAF.78
72 23 CCR § 354.16 (a-f). 73 Eastern San Joaquin 2022 GSP, Figure 2-34, p. 163. 74 Eastern San Joaquin 2022 GSP, Section 2.2.1.1, pp. 166-167. 75 Eastern San Joaquin 2022 GSP, Figure 2-37, p. 168 and Figure 2-38, p. 169. 76 Eastern San Joaquin 2022 GSP, Section 2.2.1.2, p. 167. 77 Eastern San Joaquin 2022 GSP, Section 2.2.2, p. 180 and Section 2.3.1, p. 215. 78 Eastern San Joaquin 2022 GSP, Section 2.2.2, p. 180.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 24 of 53 Regarding seawater intrusion, the GSP states that “the Eastern San Joaquin Subbasin is not in a coastal area and seawater intrusion is not present.”79 The GSP acknowledges that under natural conditions brackish tidal water from San Francisco Bay could be brought into the Delta; however, the GSP describes that man-made infrastructure, including the construction of levees and the development of the State Water Project and Central Valley Project, has altered the inward movement of seawater and current management practices aim to maintain freshwater flows in the Delta. While the GSP does not consider seawater intrusion a current concern, salinity is identified as a potential groundwater quality issue and is discussed in the GSP’s description of groundwater quality conditions.80
The GSP describes that groundwater quality in the Subbasin is generally sufficient for beneficial uses. The GSP identifies salinity, nitrate, arsenic, and point-source pollutants as the main constituents of concern in the Subbasin.81 Current and historical groundwater quality conditions are evaluated using data from the Groundwater Ambient Monitoring and Assessment (GAMA) Program. Data from the GAMA Program was used to create maps displaying maximum contaminant level (MCL) and SMCL exceedances for salinity, nitrate, and arsenic, grouped by decade. GAMA data was also summarized into tables for each constituent. The GSP uses chloride and total dissolved solids (TDS) data to evaluate salinity in the Subbasin. In general, chloride and TDS exceedances, above their 250 milligram per liter (mg/L) and 500 mg/L SMCLs, respectively, have occurred mainly along the western margin of the Subbasin both historically and in more recent times. 82 Based on data presented in the GSP, the percentage of nitrate and arsenic concentrations detected above their 10 mg/L and 10 microgram per liter MCLs, respectively, has generally increased over time. 83 The GSP does not present any intra-well time series data, so it is unclear whether the changes in the percentage of MCL or SMCL exceedances for salinity, nitrate, or arsenic indicate notable changes in groundwater quality, or whether increased sampling frequency and sampling locations are only identifying areas where groundwater quality exceedances have already been occurring. The GSP describes the presence of various point source pollutants and contaminant plumes in the Subbasin. The GSP notes that these constituents and active sites are generally regulated by the Central Valley Regional Water Quality Control Board (RWQCB), the Department of Toxic Substances Control (DTSC), and the United States Environmental Protection Agency (USEPA). 84 While historical GAMA data for groundwater quality is available and utilized by the GSP, much of the available data lacks well construction information and the GSP identifies depth-discrete groundwater quality data as a data gap.
79 Eastern San Joaquin 2022 GSP, Section 2.2.3, p. 182. 80 Eastern San Joaquin 2022 GSP, Section 2.2.3, p. 182. 81 Eastern San Joaquin 2022 GSP, Section 2.2.4, p. 182. 82 Eastern San Joaquin 2022 GSP, Section 2.2.4.1, pp. 182-192. 83 Eastern San Joaquin 2022 GSP, Section 2.2.4.2, pp. 193-195 and Section 2.2.4.3, pp. 196-198. 84 Eastern San Joaquin 2022 GSP, Section 2.2.4.4, pp. 199-203.

ATTACHMENT 2
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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 25 of 53 The GSP presents a minimal discussion on historical and current land subsidence, stating that “there are no historical records of significant and unreasonable impacts from land subsidence in the Eastern San Joaquin Subbasin.” 85 In the evaluation of current subsidence, the GSP presents a figure displaying the subsidence data from the Department’s InSAR dataset, which displays no areas of land subsidence in the Subbasin between spring 2015 and summer 2017.86
The GSP identifies depletions of interconnected surface water in the Subbasin as a data gap. Due to the lack of available data, historical and current depletions of interconnected surface water were evaluated using the historical calibration scenario of the ESJWRM.

The GSP describes that the ESJWRM was used to compare monthly groundwater levels to streambed elevations to determine where streams are interconnected.87 The GSP presents two figures summarizing the model result. Figure 2-71 displays where streams are estimated to be interconnected at least 75 percent of the time or interconnected less than 25 percent of the time. 88 Figure 2-72 displays where streams were generally considered to be gaining (groundwater discharging to stream greater than 75 percent of the time), losing (surface water seeping into groundwater system more than 75 percent of the time), or mixed (gaining or losing less than 75 percent of the time).89 The GSP does not describe the historical or current volume, rate, or timing of depletions; however, the historical, current, and projected water budgets presented in the GSP provide estimated average annual volumes of depletions (stream seepage) for the major rivers and streams in the Subbasin.90
The GSP describes the process used to identify GDEs in the Subbasin and provides multiple figures displaying the locations of GDEs or potential GDEs. The GSP describes that the NCCAG dataset was used as the starting point to identify GDEs. This dataset was then filtered based on groundwater levels and proximity to surface waters. NCCAGs in areas with groundwater levels greater than 30 feet below ground surface were not considered GDEs, as groundwater levels of that depth are considered too deep to be accessed by the vegetation. NCCAGs in close proximity to alternate water sources (including managed wetlands, irrigated agriculture, and perennial surface water bodies) were not considered GDEs, as these communities potentially rely on the alternate water sources rather than groundwater. The GSP notes that, while these NCCAG areas are not considered GDEs initially, additional investigation and ground-truthing of these areas is needed, thus, they have been classified as areas “data gap areas needing future refinement” and could potentially be included as GDEs in the future. 91 Figure 2-74 85 Eastern San Joaquin 2022 GSP, Section 2.2.5, p. 203. 86 Eastern San Joaquin 2022 GSP, Figure 2-70, p. 204.
87 Eastern San Joaquin 2022 GSP, Section 2.2.6, p. 204. 88 Eastern San Joaquin 2022 GSP, Figure 2-71, p. 206.
89 Eastern San Joaquin 2022 GSP, Figure 2-72, p. 207.
90 Eastern San Joaquin 2022 GSP, Table 2-13, p. 226.
91 Eastern San Joaquin 2022 GSP, Section 2.2.7, pp. 208-211.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 26 of 53 displays these GDE data gap areas, and Figure 2-75 displays areas presently considered to be GDEs.92
Overall, the Plan sufficiently describes the historical and current groundwater conditions throughout the Subbasin, and the information included in the Plan substantially complies with the requirements outlined in the GSP Regulations.

5.2.3 Water Budget
GSP Regulations require a water budget for the basin that provides an accounting and assessment of the total annual volume of groundwater and surface water entering and leaving the basin, including historical, current, and projected water budget conditions, and the change in the volume of water stored, as applicable.93 The water budgets and sustainable yield estimate presented in the GSP were developed using the ESJWRM, a numerical surface water-groundwater model based on the Department’s IWFM framework.94 The GSP presents historical, current, and projected water budgets, and also a water budget for projected conditions under climate change.

The historical water budget represents a 20-year period from 1996 to 2015 based on the best available historical data. The current water budget represents the current level of development (based on 2015 urban development footprint), agricultural water demand (based on 2014 cropping patterns), urban water demand (based on 2015 population), and water supply sources (based on average water supply sources from 2012 to 2015) over a 50-year hydrologic period (based on data from 1969 to 2018). The projected water budget is based on the projected changes in population, land use, and water use (not considering projects proposed by the GSP) over a 50-year hydrologic period.95 The GSP describes the assumptions used for these water budgets and presents the water budget estimates in various tables and charts.96
In response to the incomplete determination,
97 the revised GSP provided updated water
budget estimates (based on the revised ESJWRM Version 2.0 update) that extended the historical calibration scenario to 25 years, representing the time period from 1996 to 2020, and the projected conditions scenarios to 52 years. 98 Additionally, the revised GSP included an analysis on the effects of implementing 11 “Category A” projects, with and without climate change, on groundwater conditions in the Subbasin and included updated water budget estimates. 99 Based on the water budgets presented in the GSP, the Subbasin is projected to use less groundwater compared to the current groundwater demand, mainly due to the projected expansion of urban land development reducing the 92 Eastern San Joaquin 2022 GSP, Figure 2-74, p. 212 and Figure 2-75, p. 214. 93 23 CCR § 354.18 et seq. 94 Eastern San Joaquin 2022 GSP, Section 2.3.1, p. 215. 95 Eastern San Joaquin 2022 GSP, Table 2-12, p. 218. 96 Eastern San Joaquin 2022 GSP, Section 2.3.4, pp. 218-223, Section 2.3.5, pp. 223-248. 97 https://sgma.water.ca.gov/portal/service/gspdocument/download/7777. 98 Eastern San Joaquin 2022 GSP, Table 2-16, p. 232, Table 2-17, p. 234, Table 2-18, p. 236. 99 Eastern San Joaquin 2022 GSP, Appendix 2-B, pp. 1390-1562.

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Sustainable Groundwater Management Program Page 27 of 53 amount of irrigated agriculture.100 Additionally, the implementation of Category A projects is projected to result in an average annual surplus of groundwater in storage when climate change is not considered; however, with climate change considered an overdraft of 15,700 acre-feet per year is still expected even with the implementation of Category A projects.101 Selected water budget components are summarized in Table 1 below.

Table 1. Selected Water Budget Estimates102
The sustainable yield for the Subbasin was estimated using the ESJWRM under conditions describes as the “Sustainable Conditions Scenario.” This modeling scenario was based on the projected conditions scenario and was developed by adjusting (reducing) groundwater pumping across the model domain until the 50-year annual average change in groundwater storage was close to or equal to zero.103 Based on this modeling scenario, the sustainable yield for the Subbasin was estimated to be 715,000 ± 10 percent. The GSP indicates that climate change was not considered in the sustainable yield estimate. Additionally, the GSP notes that while the projected conditions scenario indicates an overdraft of only 34,000 acre-feet per year (based on the ESJWRM Version

1.0), to reach the sustainable yield approximately 78,000 acre-feet per year of additional recharge or reduced groundwater pumping would be needed.104 Based on the information presented in the GSP, it is unclear if the sustainable yield and the estimated 78,000 acrefeet per year offset are based on the updated modeling from the ESJWRM Version 1.0 or the updated ESJWRM Version 2.0.

The GSP presents various modeling results to estimate the water budgets and sustainable yield for the Subbasin (multiple scenarios from both ESJWRM Version 1.0 and ESJWRM Version 2.0). Department staff recommend that in the first periodic evaluation of the GSP, only water budgets developed from the most recent or best available data be included. As currently presented, it is unclear whether the sustainable yield estimate and estimated groundwater offset required to achieve sustainability are based on the updated modeling results (based on ESJWRM Version 2.0) or are from the 100 Eastern San Joaquin 2022 GSP, Section 2.3.5.3, p. 245. 101 Eastern San Joaquin 2022 GSP, Section 2.3.7.6.2, p. 276, Section 2.3.7.7.2, pp. 280-281. 102 Eastern San Joaquin 2022 GSP, Section 2.3.5, pp. 223-237, Section 2.3.7.6.2, p. 276, Section 2.3.7.7.2, pp. 280-281.
103 Eastern San Joaquin 2022 GSP, Section 2.3.6, pp. 248-249. 104 Eastern San Joaquin 2022 GSP, Section 2.3.6, p. 249.

Modeling Scenario Historical Current Projected Projected with Climate Change
Projected with
Category A
Projects
Projected with
Category A
Projects and
Climate Change
Model Version ESJWRM V2 ESJWRM V1 ESJWRM V2 ESJWRM V2 ESJWRM V2 ESJWRM V2 Hydrologic Period 1996-2020 1969-2018 1969-2020 1969-2020 1969-2020 1969-2020 Groundwater Pumping,
AFY 709,000 851,000 751,000 833,000 712,900 794,100
Change in GW
Storage, AFY -37,000 -48,000 -16,000 -38,000 5,300 -15,700 ATTACHMENT 2
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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 28 of 53 modeling scenarios presented in the original GSP submitted in 2020 (based on ESJWRM Version 1.0) (see Recommended Corrective Action 3).

Aside from the additional clarification requested in Recommended Corrective Action 3, Department staff conclude the historical, current, and projected water budgets included in the Plan substantially comply with the requirements outlined in the GSP Regulations.

The GSP provides the required historical, current, and future accounting and assessment of the total annual volume of groundwater and surface water entering and leaving the Subbasin including an estimate of the sustainable yield of the Subbasin and projected future water demands.

5.2.4 Management Areas
The GSP Regulations provide the option for one or more management areas to be defined within a basin if the GSA has determined that the creation of the management areas will facilitate implementation of the Plan. Management areas may define different minimum thresholds and be operated to different measurable objectives, provided that undesirable results are defined consistently throughout the basin.
105
The GSP does not designate any management areas in the Subbasin.

5.3 SUSTAINABLE MANAGEMENT CRITERIA
The GSP Regulations require each Plan to include a sustainability goal for the basin and to characterize and establish undesirable results, minimum thresholds, and measurable objectives for each applicable sustainability indicator, as appropriate. The GSP Regulations require each Plan to define conditions that constitute sustainable groundwater management for the basin including the process by which the GSA characterizes undesirable results and establishes minimum thresholds and measurable objectives for each applicable sustainability indicator.106

5.3.1 Sustainability Goal
The GSP describes that the sustainability goal for the Subbasin is “to maintain an economically-viable groundwater resource for the beneficial use of the people of the Eastern San Joaquin Subbasin by operating the Subbasin within its sustainable yield or by modification of existing management to address future conditions.”107 The GSP states that sustainability will be achieved through the implementation of both supply and demand type projects. While the GSP acknowledges that groundwater levels may continue to decline throughout GSP implementation, the GSP also states that the Subbasin will be managed to avoid undesirable results during the implementation period.108 105 23 CCR § 354.20.
106 23 CCR § 354.22 et seq. 107 Eastern San Joaquin 2022 GSP, Section 3.1, p. 287. 108 Eastern San Joaquin 2022 GSP, Section 3.1, p. 287.

5.3.2 Sustainability Indicators
Sustainability indicators are defined as any of the effects caused by groundwater conditions occurring throughout the basin that, when significant and unreasonable, cause undesirable results.109 Sustainability indicators thus correspond with the six undesirable results – chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon, significant and unreasonable reduction of groundwater storage, significant and unreasonable seawater intrusion, significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies, land subsidence that substantially interferes with surface land uses, and depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water110 – but refer to groundwater conditions that are not, in and of themselves, significant and unreasonable. Rather, sustainability indicators refer to the effects caused by changing groundwater conditions that are monitored, and for which criteria in the form of minimum thresholds are established by the agency to define when the effect becomes significant and unreasonable, producing an undesirable result.

The following subsections include details about three facets of sustainable management criteria: undesirable results, minimum thresholds, and measurable objectives for each sustainability indicator. GSAs are not required to establish criteria for undesirable results that the agency can demonstrate are not present and are not likely to occur in a basin. 111

5.3.2.1 Chronic Lowering of Groundwater Levels
The GSP Regulations require the minimum threshold for chronic lowering of groundwater levels to be the groundwater elevation indicating a depletion of supply at a given location that may lead to undesirable results.
112
The GSP describes that an undesirable result for the chronic lowering of groundwater levels in the Eastern San Joaquin Subbasin is experienced “if sustained groundwater levels are too low to satisfy beneficial uses within the Subbasin over the planning and implementation horizon of this GSP.” The GSP also lists potential undesirable results identified by stakeholders as significant and unreasonable:
• Number of wells going dry
• Reduction in the pumping capacity of existing wells
• Increase in pumping costs due to greater lift
• Need for deeper well installations or lowering of pumps 109 23 CCR § 351(ah).
110 Water Code § 10721(x).
111 23 CCR § 354.26(d).
112 23 CCR § 354.28(c)(1).

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Sustainable Groundwater Management Program Page 30 of 53 • Adverse impacts to environmental uses and users, including interconnected surface waters and GDEs113
The GSP describes a quantitative identification of undesirable results for the chronic lowering of groundwater levels as occurring when “at least 25 percent of representative monitoring wells used to monitor groundwater levels (5 of 20 wells in the Subbasin) fall below their minimum level thresholds for two consecutive years.”114 These conditions were described by the GSP as being sufficient to identify a Subbasin-wide pattern of undesirable results, rather than either geographically-localized conditions or temporally isolated events.115
Minimum thresholds for the chronic lowering of groundwater levels were established for 20 representative monitoring wells.116 The GSP describes the process for developing minimum thresholds, which included reviewing historic groundwater levels and existing groundwater-related planning documents, an analysis of nearby domestic or municipal supply well depths, and obtaining input from GSAs, the ESJGWA Advisory Committee, the ESJGWA Workgroup, and other stakeholders. To develop the minimum thresholds, the fall 1992 groundwater levels were first selected, as this period was identified in existing planning documents as a time of historic lows. The fall 1992 groundwater levels were then compared to both fall 2015 and fall 2016 groundwater levels to see whether groundwater levels declined even further during more recent drought periods. The GSAs then confirmed, either anecdotally or through an evaluation of available data, that no undesirable results occurred when groundwater levels were at their historic low values (whichever was deeper of the fall 1992 or fall 2015-2016 periods). Using these historic low groundwater levels as a starting point, a buffer was then added which would allow the groundwater levels to drop below historic low values while allowing operational flexibility.

The buffer was developed by calculating the historic range of groundwater level fluctuations for each representative well (the historic high minus the historic low) and subtracting this value from the historic low. These calculated values (the historic low minus the buffer) were presented as the initial minimum threshold values.117 The GSP describes that the protection of existing water supply wells was considered a priority when developing the minimum thresholds, so the initial minimum threshold values were then compared to the 10th percentile of domestic well depth for domestic wells (with well construction information in the OSWCR database) within a 3-mile radius of each representative monitoring well.118 For areas reliant on municipal supply wells, the 10th percentile of municipal supply well depth was used for the analysis. For each representative monitoring well, if the initial minimum threshold value (historic low minus buffer) was shallower than the 10th percentile well depth value, it was considered 113 Eastern San Joaquin 2022 GSP, Section 3.3.1.1.1, pp. 289-290. 114 Eastern San Joaquin 2022 GSP, Section 3.3.1.1.2, p. 290. 115 Eastern San Joaquin 2022 GSP, Section 3.3.1.1.2, p. 290. 116 Eastern San Joaquin 2022 GSP, Table 3-1, p. 296.
117 Eastern San Joaquin 2022 GSP, Section 3.3.1.2, pp. 291-293. 118 Eastern San Joaquin 2022 GSP, Section 3.3.1.2, p. 292.

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Sustainable Groundwater Management Program Page 31 of 53 sufficiently protective of nearby supply wells (domestic or municipal). If the initial minimum threshold value was deeper than the 10th percentile well depth value, then the 10th percentile well depth value was used for the minimum threshold. Overall, the GSP estimates that this analysis should be protective of approximately 90 percent of domestic or municipal wells in the Subbasin.119 The GSP presents a summary table of the data used for the minimum threshold analysis, which indicates that the final minimum thresholds selected for the 20 representative monitoring wells range from 22.5 to 242.7 feet below ground surface, and the potential groundwater level declines below historic lows range from 7.3 to 54.4 feet.120 The GSP describes that the final minimum threshold values, even though they allow for groundwater levels declines below historic lows, were considered to be sufficiently protective of undesirable results by the individual GSAs; however, the GSP notes that undesirable results related to GDEs is considered a data gap.121 Additionally, the GSP describes that an adaptive management approach will be utilized, and if the established minimum thresholds result in impacts to groundwater users during implementation, minimum threshold may be revised, or additional projects or management actions may be implemented.122
The GSP defines the measurable objectives for the Subbasin as the deeper value of the fall 1992, fall 2015, or fall 2016 groundwater levels for each representative monitoring well. The GSP describes that these values were selected to allow for operational flexibility and active management of the Subbasin during dry periods without reaching minimum threshold values.123 The GSP indicates that GSAs identified no undesirable results when historic groundwater levels were at these measurable objective values. 124 Interim milestones presented in the GSP represent stepwise trends from the current conditions (defined as fall 2015 groundwater levels) to the measurable objective, designated in fiveyear intervals from 2030 to 2040. The GSP indicates that the interim milestones remain the same as current conditions for the first 10 years of GSP implementation. In general, measurable objectives allow for declining groundwater levels compared to current conditions; however, because the current conditions are represented by fall 2015 data and some measurable objectives are also based on fall 2015 data, some representative monitoring wells are already at their measurable objective and, thus, have a goal of keeping groundwater levels at those locations stable through the implementation period.

The GSP presents a summary table with current conditions, measurable objectives, and interim milestones for each representative monitoring well.125 Department staff conclude that the sustainable management criteria for the chronic lowering of groundwater levels are commensurate with the understanding of current conditions and reasonably protective of the groundwater uses and users in the Subbasin. 119 Eastern San Joaquin 2022 GSP, Section 3.3.1.2, p. 293. 120 Eastern San Joaquin 2022 GSP, Appendix 3-A, p. 1564. 121 Eastern San Joaquin 2022 GSP, Section 3.3.1.1.4, p. 291 and Section 3.3.1.2, p. 292. 122 Eastern San Joaquin 2022 GSP, Section 3.3.1.2, pp. 293-294. 123 Eastern San Joaquin 2022 GSP, Section 3.3.1.3, p. 297. 124 Eastern San Joaquin 2022 GSP, Section 3.3.1.2, p. 292. 125 Eastern San Joaquin 2022 GSP, Table 3-3, p. 298.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 32 of 53 While groundwater levels may continue to decline during implementation, the Plan provides a credible and sufficient assessment of the impacts the minimum thresholds would have on domestic and municipal supply wells by evaluating the 10th percentile well depths and comparing that to the initial minimum threshold values (based on the historic lows with a buffer) to establish the minimum thresholds at individual representative monitoring points which, if not exceeded, are protective of approximately 90-percent of domestic or municipal wells in the Subbasin. However, as highlighted in the recommended corrective actions described in the review of Deficiency 1, the GSP should include some additional supporting technical details that provide further description potential impacts related to the defined minimum thresholds.

5.3.2.2 Reduction of Groundwater Storage
The GSP Regulations require the minimum threshold for the reduction of groundwater storage to be a total volume of groundwater that can be withdrawn from the basin without causing conditions that may lead to undesirable results. Minimum thresholds for reduction of groundwater storage shall be supported by the sustainable yield of the basin, calculated based on historical trends, water year type, and projected water use in the basin.
126
The GSP describes that an undesirable result for the reduction of groundwater storage occurs when “sustained groundwater storage volumes are insufficient to satisfy beneficial uses within the Subbasin over the planning and implementation horizon of this GSP.”127 The GSP describes how the Subbasin contains approximately 53 MAF of fresh groundwater in the aquifer, and historically there have been no undesirable results related to the reduction of groundwater storage. The GSP estimates a total volume of 23 MAF which, if depleted, would result in undesirable results for the Subbasin. This volume was estimated based on the depths of existing well infrastructure and potential future depths to which pumping would reasonably occur.128 The GSP indicates that a reduction of groundwater in storage of this magnitude is highly unlikely during the implementation period, as modeling results only estimate a -0.91 MAF cumulative change in storage from 1996 to 2015.129 While it may be unlikely to reduce groundwater in storage by 23 MAF before projects are implemented and sustainability is achieved, Department staff believe this estimate to be misleading, as there would likely be significant and unreasonable impacts prior to reaching a depletion of 23 MAF. For example, the GSP appears to be implying that a reduction of less than 23 MAF (e.g., 22 MAF) would not result in significant and unreasonable impacts to shallow groundwater users. While it is understandable that groundwater level sustainable management criteria will likely prevent reductions of groundwater in storage of this magnitude, Department staff feel that the estimate provided by the GSP is unreasonable and misleading regarding impacts to beneficial uses and users and should be revised. Department staff recommend the GSP provide a revised 126 23 CCR § 354.28(c)(2).
127 Eastern San Joaquin 2022 GSP, Section 3.3.2.1.1, p. 299. 128 Eastern San Joaquin 2022 GSP, Section 3.3.2.1.2, p. 299. 129 Eastern San Joaquin 2022 GSP, Section 2.2.2, p. 180.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 33 of 53 estimate for the reduction of groundwater storage volume that is considered an undesirable result. Alternatively, the GSP could highlight how the maximum reduction of groundwater storage related to the chronic lowering of groundwater level minimum thresholds would not result in significant and unreasonable impacts related to groundwater storage and omit the 23 MAF estimate (see Recommended Corrective Action 4).

The GSP proposes to use sustainable management criteria developed for the chronic lowering of groundwater levels as a proxy for reductions of groundwater storage. These criteria include the same minimum thresholds, measurable objectives, interim milestones, and representative monitoring network as described above for groundwater levels. The GSP indicates that if groundwater levels are maintained at the minimum threshold values across the Subbasin, the resulting reduction of groundwater in storage is estimated to be

1.2 MAF, which would not be considered an undesirable result.130 Overall, Department staff conclude that the use of groundwater levels as a proxy for the reduction of groundwater storage to be appropriate, as the potential impacts related to reductions of groundwater storage are similar to those described for the chronic lowering of groundwater levels. Additionally, the GSP indicated that no undesirable results related to the reduction of groundwater in storage have occurred historically, thus, once sustainability is achieved and groundwater levels are maintained near measurable objective levels (which are generally based on historic lows), there should be no associated undesirable results.

5.3.2.3 Seawater Intrusion
The GSP Regulations require the minimum threshold for seawater intrusion to be defined by a chloride concentration isocontour for each principal aquifer where seawater intrusion may lead to undesirable results.
131
The GSP describes that an undesirable result related to seawater intrusion is experienced “if sustained groundwater salinity levels caused by seawater intrusion and due to groundwater management practices are too high to satisfy beneficial uses within the basin over the planning and implementation horizon of this GSP.”132 The GSP describes that the Subbasin is not in a coastal area and seawater intrusion is not currently present because Delta management practices have limited the inward movement of seawater to maintain freshwater flows in the Delta.133 The GSP states that undesirable results related to seawater intrusion are not expected to occur in the future; however, the GSP acknowledges that because the Subbasin is adjacent to the Delta, changes in Delta management practices or sea level rise due to climate change could potentially result in seawater intrusion in the future.
130 Eastern San Joaquin 2022 GSP, Section 3.3.2.2, pp. 299-300. 131 23 CCR § 354.28(c)(3).
132 Eastern San Joaquin 2022 GSP, Section 3.3.4.1.1, p. 306. 133 Eastern San Joaquin 2022 GSP, Section 2.2.3, p. 182.

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Sustainable Groundwater Management Program Page 34 of 53 The GSP defines sustainable management criteria for seawater intrusion with the use of a pre-defined chloride isocontour line.134 This line is described as “a demarcation of where the ESJGWA would consider seawater intrusion an undesirable result.”135 The minimum threshold for seawater intrusion is defined as this isocontour line at a chloride concentration value of 2,000 mg/L. The GSP identifies an undesirable result related to seawater intrusion as occurring when a 2,000 mg/L chloride isocontour line created using current data from the groundwater quality monitoring network crosses this pre-defined isocontour line. The measurable objective for seawater intrusion is defined using a 500 mg/L isocontour line demarked using the same isocontour line as the minimum threshold.

The GSP indicates that interim milestones will follow a linear trend in five-year increments between the current conditions and the measurable objectives; however, the Plan provides no estimates of current conditions, so it is unclear whether measurable objectives proposed to allow for further degradation of groundwater quality or propose to improve groundwater quality over the implementation period.

Based on the figure, the pre-defined isocontour line is located in the western portion of the Subbasin and bisects the cities of Stockton and Manteca. The Plan does not provide a description for how the 2,000 mg/L threshold value would prevent significant and unreasonable impacts to groundwater users. Considering that the “recommended” SMCL for chloride is 250 mg/L and the SMCL “upper limit” is 500 mg/L, a chloride concentration of almost 2,000 mg/L (yet staying below the minimum threshold) would appear to be a significant degradation of groundwater quality that is not discussed by the Plan, particularly because the western portion of the Subbasin where seawater intrusion could potentially occur contains the Subbasin’s larger cities where a larger portion of population may depend on groundwater for potable uses.

While Department staff believe the methodology and use of a chloride isocontour line to define sustainable management criteria to be reasonable and agree that seawater intrusion into the Subbasin may be unlikely in the near term, the Plan does not provide sufficient explanation describing how impacts to beneficial uses and users were considered when selecting the 2,000 mg/L minimum threshold. Department staff recommend the GSP provide additional explanation for how the 2,000 mg/L chloride isocontour line will prevent significant and unreasonable impacts to beneficial uses and users of groundwater. Even though seawater intrusion may be unlikely in the Subbasin, the currently defined minimum thresholds could allow for groundwater beneath the cities of Stockton and Manteca to approach chloride concentrations of almost 2,000 mg/L. If the GSAs consider this to be insignificant, considering the upper limit SMCL for chloride is 1,000 mg/L, the justification should be described and disclosed in the Plan. Additionally, the Plan should provide the current chloride conditions and interim milestones for seawater intrusion. As currently presented, the Plan does not describe these values and Department staff cannot determine whether the proposed measurable objective based on 134 Eastern San Joaquin 2022 GSP, Figure 3-4, p. 307.
135 Eastern San Joaquin 2022 GSP, Section 3.3.4.2, p. 307.

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Sustainable Groundwater Management Program Page 35 of 53 the 500 mg/L chloride isocontour line result in groundwater quality degradation or improvement over the implementation period (see Recommended Corrective Action 5).

5.3.2.4 Degraded Water Quality
The GSP Regulations require the minimum threshold for degraded water quality to be the degradation of water quality, including the migration of contaminant plumes that impair water supplies or other indicator of water quality as determined by the Agency that may lead to undesirable results. The minimum threshold shall be based on the number of supply wells, a volume of water, or a location of an isocontour that exceeds concentrations of constituents determined by the Agency to be of concern for the basin. In setting minimum thresholds for degraded water quality, the Agency shall consider local, state, and federal water quality standards applicable to the basin. 136
The GSP describes that an undesirable result for degraded groundwater quality “is experienced if SGMA-related groundwater management activities cause significant and unreasonable impacts to the long-term viability of domestic, agricultural, municipal, environmental, or other beneficial uses over the planning and implementation horizon of this GSP.” 137 The GSP identifies salinity, arsenic, nitrate, and various point source contaminants as the main constituents of concern in the Subbasin; however, sustainable management criteria are only defined for salinity (through the measurement of total dissolved solids concentrations).138 The GSP describes that nitrate, arsenic, and point source contaminants are generally regulated through other programs and agencies, such as the Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) and the Irrigated Lands Regulatory Program (ILRP), and other programs through the RWQCB, DTSC, and USEPA.139 Additionally, the GSP describes how currently there is no known causal nexus between nitrate or arsenic and groundwater management activities.140 Even though no sustainable management criteria were established for some constituents of concern, the GSP describes that data from other programs will be evaluated in conjunction with groundwater level data to determine whether groundwater management activities or SGMA-related projects result in impacts relating to these constituents.141 The GSP also commits to collecting arsenic and nitrate data from the Subbasin’s groundwater quality network to evaluate trends and potentially establish sustainable management criteria for these constituents in the future, if warranted.142 The GSP defines sustainable management criteria for degraded water quality using TDS as an indicator of salinity. An undesirable result is defined as when more than 25 percent of representative groundwater quality monitoring wells (at least 3 of 10) exceed the minimum threshold for two consecutive years and where these concentrations are the 136 23 CCR § 354.28(c)(4).
137 Eastern San Joaquin 2022 GSP, Section 3.3.3.1.1, p. 300. 138 Eastern San Joaquin 2022 GSP, Section 2.2.4, p. 182. 139 Eastern San Joaquin 2022 GSP, Section 3.3.3.1.1, p. 301. 140 Eastern San Joaquin 2022 GSP, Section 2.2.4.2, p. 193 and Section 2.2.4.3, p. 196. 141 Eastern San Joaquin 2022 GSP, Appendix 3-E, p. 1623. 142 Eastern San Joaquin 2022 GSP, Section 3.3.3.4, p. 305.

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Sustainable Groundwater Management Program Page 36 of 53 result of groundwater management activities. The GSP indicates that changes to groundwater quality will be evaluated on an annual basis to determine whether groundwater management has contributed to groundwater quality degradation.143 The GSP describes the potential causes of undesirable results and the possible effects on beneficial users and land use if undesirable results were to occur. 144
The GSP defines the minimum threshold for TDS as a concentration of 1,000 mg/L for all groundwater quality representative monitoring wells. The GSP describes that the minimum threshold was developed with stakeholder input and based on concerns for both drinking water and agricultural users. The GSP states that the minimum threshold is equal to the State Water Resources Control Board Division of Drinking Water’s (DDW) SMCL “upper limit” for TDS, which is a value defined for aesthetic reasons, rather than public health concerns. Additionally, the Plan describes that the major crops grown in the Subbasin can generally tolerate TDS ranges from 900 mg/L to 4,000 mg/L, thus, the 1,000 mg/L minimum threshold values is considered protective of the majority of Subbasin crops.145
Measurable objectives for degraded groundwater quality are defined as 600 mg/L TDS concentrations for all groundwater quality representative monitoring wells. The GSP describes that, while the DDW’s SMCL “recommended limit” is defined as 500 mg/L, this value is based on aesthetic concerns and 600 mg/L is generally considered adequate for both drinking water and agricultural purposes. The Plan provides a table displaying current conditions for the representative monitoring wells (based on the average TDS concentrations for data available in recent years) compared to measurable objectives and interim milestones. The current conditions range from 280 mg/L to 510 mg/L TDS, indicating that the measurable objective allows for declining groundwater quality throughout the implementation period. The Interim milestones are defined based on a linear trend from the current conditions to the measurable objectives.

Department staff conclude that the proposed sustainable management criteria appear reasonable, even though the measurable objectives generally allow for a decline in groundwater quality compared to current conditions. While the GSP only sets sustainable management criteria for TDS, the commitment to monitoring for arsenic and nitrate and the proposed groundwater quality evaluation, coordination, data management, and reporting processes outlined by the Plan146 and discussed previously in the review of Deficiency 1 appear to be sufficient to identify groundwater quality degradation that may occur in the future and can be adaptively managed by the GSAs.

5.3.2.5 Land Subsidence
SGMA defines the undesirable result for subsidence to be significant and unreasonable land subsidence that substantially interferes with surface land uses, caused by 143 Eastern San Joaquin 2022 GSP, Section 3.3.3.1.2, p. 301. 144 Eastern San Joaquin 2022 GSP, Section 3.3.3.1.3, p. 301 and Section 3.3.3.1.4, p. 302. 145 Eastern San Joaquin 2022 GSP, Section 3.3.3.2, p. 302. 146 Eastern San Joaquin 2022 GSP, Section 3.3.3.2, p. 304.

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San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 37 of 53 groundwater conditions occurring throughout the basin.147 The GSP Regulations require the minimum threshold for land subsidence to be the rate and extent of subsidence that substantially interferes with surface land uses and may lead to undesirable results.148 Minimum thresholds for subsidence shall be supported by the identification of land uses and property interests that have been affected or are likely to be affected by land subsidence in the basin, including an explanation of how the Agency has determined and considered those uses and interests, and the Agency’s rationale for establishing minimum thresholds in light of those effects and maps and graphs showing the extent and rate of land subsidence in the basin that defines the minimum threshold and measurable objectives.149
The GSP states that an undesirable result for land subsidence “is experienced if the occurrence of land subsidence substantially interferes with beneficial uses of groundwater and infrastructure within the Subbasin over the planning and implementation horizon of this GSP.”150 The GSP identifies general types of critical infrastructure in the Subbasin as:
• Major highways, roadways, and bridges
• Canals, pipelines, and levees
• Electrical transmission lines
• Schools
• Fire stations
• Hospitals and other medical facilities
• Law enforcement facilities (police stations, jails, correctional facilities) • Water and wastewater treatment, distribution, and storage facilities • Communication facilities151
While general infrastructure types are identified by the Plan, specific locations of infrastructure and the rate and extent of subsidence that would potentially cause impacts to the different infrastructure types was not described. The GSP indicates that specific infrastructure was not identified due to “the sensitive nature of the critical infrastructure.”152 The GSP indicates that the San Joaquin County Office of Emergency Services was consulted to determine the total subsidence the critical infrastructure can tolerate. From these discussions, the GSP only describes that the critical infrastructure can tolerate “a significant amount of uniform settlement due to subsidence across the Subbasin, though the total amount of settlement that can be tolerated is dependent on the design of the specific infrastructure.”153
147 Water Code § 10721(x)(5). 148 23 CCR § 354.28(c)(5). 149 23 CCR §§ 354.28(c)(5)(A-B).
150 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.1, p. 308. 151 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.1, p. 308. 152 Eastern San Joaquin 2022 GSP, Appendix 3-F, p. 1631. 153 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.1, p. 309.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 38 of 53 The GSP does not provide a quantifiable metric that would identify undesirable results related to land subsidence. The GSP only states that “[a]n undesirable result occurs when subsidence substantially interferes with beneficial uses of groundwater and surface land uses.” Additionally, the GSP states that undesirable results related to land subsidence will be identified using data collected from the (groundwater level) representative monitoring network, data collected by individual GSAs, and additional available data such as continuous GPS, InSAR, and data from UNAVCO’s Plate Boundary Observatory Program.154 While the potential for land subsidence in the Subbasin may be low based on the absence of historical land subsidence, GSP Regulations require that undesirable results be defined using a quantitative combination minimum threshold exceedances (see Recommended Corrective Action 2).

The representative groundwater level monitoring network and associated minimum thresholds are used as a proxy to define minimum thresholds for land subsidence. These minimum thresholds, based on the historic low water levels plus a buffer or the 10th percentile domestic/municipal well depth, allow for groundwater levels to drop below historic lows by approximately 7 to 54 feet, depending on well location. The GSP describes that these groundwater levels are considered protective of impacts caused by land subsidence because if the minimum thresholds are not exceeded, the additional declines in groundwater levels below historic lows are limited to geologic units that have historically not been prone to subsidence. 155 While Department staff believe this argument understandable, the GSP does not provide an analysis that takes into consideration potential minimum threshold exceedances, which could be allowed in the representative monitoring wells based on the proposed metrics used to identify an undesirable result for the chronic lowering of groundwater levels (i.e., an undesirable result is defined as minimum threshold exceedances in 5 of 20 monitoring wells for two consecutive years).

In addition to the use of groundwater levels as a proxy for land subsidence minimum thresholds, measurable objectives and interim milestones for groundwater levels are used as a proxy to define those same metrics for land subsidence.156 Measurable objectives are based on the historic low groundwater levels and interim milestones are defined as a linear trend from the current conditions to the measurable objectives. Based on these values, if groundwater levels were maintained at the measurable objectives (i.e., historic lows), the potential for land subsidence would, in theory, be minimal.

The GSP states that the use of groundwater levels as a proxy is necessary “given the relative lack of direct monitoring for land subsidence in the Subbasin.” The GSP also describes how additional land subsidence monitoring data (such as CGPS and InSAR data) will be evaluated in conjunction with groundwater levels to further evaluate the 154 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.2, p. 309. 155 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.2, p. 310. 156 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.2, p. 310.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 39 of 53 correlation.
157 In general, Department staff conclude these statements are contradictory, and it is unclear as to why the GSP does not establish sustainable management criteria for land subsidence using the available InSAR dataset that provides direct monitoring for land subsidence Subbasin-wide (see Recommended Corrective Action 2).

Even though the GSP proposes to use groundwater levels as a proxy for land subsidence minimum thresholds, the Plan also defines a “trigger value” of 0.25 feet of annual subsidence (from direct land subsidence monitoring data sources) that will initiate an analysis to determine whether subsidence is related to groundwater management activities. Based on results of this analysis, additional projects or management actions could be implemented.158 Department staff conclude the commitment to evaluating direct subsidence monitoring data to be a step in the right direction; however, the GSP provides no details on the proposed “analysis” that will be conducted.

Based on the information presented in the GSP, Department staff agree that the potential for land subsidence in the Subbasin is generally lower than neighboring Subbasins that contain regionally extensive thick units of compressible clays, such as the Corcoran Clay.

However, GSP Regulations require that minimum thresholds be defined by a rate and extent of land subsidence that could substantially interfere with land uses and may lead to undesirable results. While GSP Regulations allow for groundwater levels to be used as a proxy for other sustainability indicators, the GSP fails to provide the necessary supporting evidence sufficient to show how the established minimum thresholds and, particularly, the identification of undesirable results which allow minimum thresholds to be exceeded, will prevent significant and unreasonable impacts caused by land subsidence.

5.3.2.6 Depletions of Interconnected Surface Water
SGMA defines undesirable results for the depletion of interconnected surface water as those that have significant and unreasonable adverse impacts on beneficial uses of surface water and are caused by groundwater conditions occurring throughout the basin.159 The GSP Regulations require that a Plan identify the presence of interconnected surface water systems in the basin and estimate the quantity and timing of depletions of those systems.160 The GSP Regulations further require that minimum thresholds be set based on the rate or volume of surface water depletions caused by groundwater use, supported by information including the location, quantity, and timing of depletions, that adversely impact beneficial uses of the surface water and may lead to undesirable results.161
The GSP defines an undesirable result related to depletions of interconnected surface water as “depletions that result in flow or levels of major rivers and streams that are 157 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.2, p. 310. 158 Eastern San Joaquin 2022 GSP, Section 3.3.5.1.2, p. 310. 159 Water Code § 10721(x)(6).
160 23 CCR § 354.16(f).
161 23 CCR § 354.28(c)(6).

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 40 of 53 hydrologically connected to the basin such that the reduced surface water flow or levels have a significant and unreasonable adverse impact on beneficial uses and users of the surface water within the Subbasin over the planning and implementation horizon of this GSP.”162 The GSP indicates that depletions leading to undesirable results could result in a reduction in the flows in major rivers and streams such that there is insufficient surface water available to support diversions or to meet regulatory environmental flow requirements. The GSP identifies the Calaveras River, Dry Creek, the Mokelumne River, the San Joaquin River, and the Stanislaus River as the major rivers and streams that are potentially interconnected to the groundwater system in the Subbasin. Of these, the GSP indicates that the Mokelumne, Stanislaus, and San Joaquin rivers have defined regulatory flow requirements that are managed through various upstream reservoirs. The GSP notes that smaller creeks and streams in the Subbasin were not considered in the evaluation of depletions of interconnected surface water, as they are “substantially used for the conveyance of irrigation water.”163
The GSP does not estimate the quantity, location, or timing of depletions that would result in significant and unreasonable impacts to surface water diverters or environmental users.

Additionally, the GSP does not quantify what would be considered an undesirable result in terms of depletion. Instead, the GSP proposes to use the already defined groundwater level sustainable management criteria as a proxy for depletions of interconnected surface water (including minimum thresholds, measurable objectives, and interim milestones).

Rather than defining groundwater level thresholds that are a proxy for the specific quantity of depletion that could cause undesirable results, the GSP argues that the minimum thresholds developed for chronic lowering of groundwater levels (which were informed by factors including domestic well depths), would protect against stream depletion undesirable results. In other words, the GSP implies that undesirable quantities of stream depletion, whatever that would be, would not occur unless groundwater levels fell below the chronic lowering of groundwater level minimum thresholds and, because that scenario would trigger an undesirable result related to the chronic lowering of groundwater levels, an undesirable result for depletions of interconnected surface water would be preemptively avoided.

In supporting the argument that groundwater level minimum thresholds would prevent undesirable results related to depletions of interconnected surface water, the GSP attempts to quantify the additional depletions that would be associated with groundwater level undesirable results. The GSP appears to quantify these additional depletions solely by comparing depletions estimated in the projected conditions modeling scenario to depletions estimated in the historical conditions modeling scenario (rather than by estimating depletions specifically associated with groundwater levels at minimum threshold values). As described previously, the historical conditions scenario represents the historical water budget and hydrologic conditions for a 20-year period from 1996 to 162 Eastern San Joaquin 2022 GSP, Section 3.3.6.1.2, p. 311. 163 Eastern San Joaquin 2022 GSP, Section 3.3.6.1, p. 311.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 41 of 53 2015. The projected conditions scenario represents a 50-year period with the projected groundwater and surface water demand based on projected future changes in land use, population, and water supplies. While not many details are presented, the GSP states that the additional depletions occurring in the projected conditions scenario average 50,000 acre-feet per year compared to the historical conditions scenario.164 The GSP indicates that these additional depletions are approximately one percent of total annual stream outflows and, thus, argues that depletions of this magnitude are not likely to cause impacts. Department staff conclude, generally, that arguments stating a particular effect is small relative to a large annual amount are not compelling. Comparing depletion quantity due to groundwater use in any Subbasin to the total annual surface water outflow from a large watershed will, in most, if not all, cases, show that the depletion quantity is small relative to the total annual outflow. Comparing to the total annual outflow is not, as a long-term solution to groundwater management, the only relevant metric. It ignores potential temporal or seasonal effects, where flows during certain (e.g., drier) times of the year may have a higher potential to be unreasonably or significantly affected by depletions that may appear small at other times or in the aggregate.

While Department staff generally conclude the GSP’s discussion of stream depletion sustainable management criteria to be lacking sufficient detail, Department staff at this time do not believe that this issue substantially affects the immediate and near-term implementation of the GSP’s management regime or the likelihood of the Subbasin to achieve its sustainability goals within 20 years. Based on the water budgets presented in the GSP and the additional modeling results which estimate the effects of implementing Category A projects (described in Section 5.5 below), the Subbasin’s management strategy should result in reduced groundwater use over the GSP implementation period as compared to the current or baseline groundwater demand. Department staff recognize that, in general, when there is an interconnection between the surface water and groundwater systems, a reduction in groundwater use will generally have an associated reduction of streamflow depletions over the long term. Department staff also recognize that depletions of interconnected surface water has been identified as a data gap area by the GSP.

Due to these factors, Department staff do not consider the shortcoming of the current plan to preclude approval. Department staff understand that quantifying depletions of interconnected surface water from groundwater extractions is a complex task that likely requires developing new, specialized tools, models, and methods to understand local hydrogeologic conditions, interactions, and responses. During the initial review of GSPs, Department staff have observed that most GSAs have struggled with this requirement of SGMA. However, staff believe that most GSAs will more fully comply with regulatory requirements after several years of Plan implementation that includes projects and management actions to address the data gaps and other issues necessary to understand, quantify, and manage depletions of interconnected surface waters. Department staff 164 Eastern San Joaquin 2022 GSP, Section 3.3.6.2, p. 312.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 42 of 53 further advise that at this stage in SGMA implementation GSAs address deficiencies related to interconnected surface water depletion where GSAs are still working to fill data gaps related to interconnected surface water and where these data will be used to inform and establish sustainable management criteria based on timing, volume, and depletion as required by the GSP Regulations (see Recommended Corrective Action 6a).

The Department will continue to support GSAs in this regard by providing, as appropriate, financial and technical assistance to GSAs, including the development of guidance describing appropriate methods and approaches to evaluate the rate, timing, and volume of depletions of interconnected surface water caused by groundwater extractions. Once the Department’s guidance related to depletions of interconnected surface water is publicly available, GSAs, where applicable, should consider incorporating appropriate guidance approaches into their future periodic evaluations to the GSP (see Recommended Corrective Action 6a). GSAs should consider availing themselves of the Department’s financial or technical assistance, but in any event must continue to fill data gaps, collect additional monitoring data, and implement strategies to better understand and manage depletions of interconnected surface water caused by groundwater extractions and define segments of interconnectivity and timing within their jurisdictional area (see Recommended Corrective Action 6b). Furthermore, GSAs should coordinate with local, state, and federal resources agencies as well as interested parties to better understand the full suite of beneficial uses and users that may be impacted by pumping induced surface water depletion (see Recommended Corrective Action 6c).

5.4 MONITORING NETWORK
The GSP Regulations describe the monitoring network that must be developed for each basin including monitoring objectives, monitoring protocols, and data reporting requirements. Collecting monitoring data of a sufficient quality and quantity is necessary for the successful implementation of a groundwater sustainability plan. The GSP Regulations require a monitoring network of sufficient quality, frequency, and distribution to characterize groundwater and related surface water conditions in the basin and evaluate changing conditions that occur through implementation of the Plan. 165 Specifically, a monitoring network must be able to monitor impacts to beneficial uses and users,
166 monitor changes in groundwater conditions relative to measurable objectives and minimum thresholds, 167 capture seasonal low and high conditions, 168 include required information such as location and well construction, and include maps and tables clearly showing the monitoring site type, location and frequency.169 Department staff encourage GSAs to collect monitoring data as specified in the GSP, fill data gaps 165 23 CCR § 354.32.
166 23 CCR § 354.34(b)(2).
167 23 CCR § 354.34(b)(3).
168 23 CCR § 354.34(c)(1)(B).
169 23 CCR §§ 354.34(g-h).

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 43 of 53 identified in the GSP prior to the first periodic evaluation, 170 update monitoring network
information as needed, follow monitoring best management practices, 171 and submit all
monitoring data to the Department’s Monitoring Network Module immediately after collection including any additional groundwater monitoring data that is collected within the Plan area that is used for groundwater management decisions. Staff note that if GSAs do not fill their identified data gaps, the GSA’s basin understanding may not represent the best available science for use to monitor basin conditions.

The monitoring network for the chronic lowering of groundwater levels includes 127 existing wells that will be measured semi-annually in March and October. The 127 wells are categorized into either the representative monitoring well network with 20 wells that will be used to evaluate compliance with sustainable management criteria, or the broad monitoring network with 107 wells that will be used to collect supplemental data throughout the Subbasin. The GSP includes figures that show the well locations and also tables that summarize well details such as well names, well construction information (if available), and monitoring agencies.172 The GSP estimates that the spatial density of the combined groundwater level network is 10.6 wells per 100 square miles, and the representative monitoring well network is 1.7 wells per 100 square miles.173 The GSP identifies data gaps for the groundwater level monitoring network as areas near streams and Subbasin boundaries, near the groundwater depression in the central portion of the Subbasin, and depth-discrete groundwater level data (i.e., a lack of multi-completion monitoring wells).174 Additionally, data gaps identified for the hydrogeologic conceptual model indicated that there are groundwater level data gaps in the east and northwest portions of the Subbasin, and also for shallow groundwater levels near NCCAGs.175 The GSP indicates that the plan to address these data gaps includes the construction of 12 new monitoring wells. Two of the new wells will be multi-completion monitoring wells, with one located along the northern boundary near Dry Creek, and the other located in the central portion of the Subbasin. The remaining 10 new wells will be shallow wells near streams, Subbasin boundaries, and the central groundwater depression.176 Proposed well locations are displayed on a map with the existing monitoring network well locations.177
Groundwater storage will be monitored using the groundwater level monitoring network.178 Because groundwater levels are used as a proxy for groundwater storage sustainable management criteria, Department staff believe that the use of the 170 23 CCR § 354.38(d).
171 Department of Water Resources, 2016, Best Management Practices and Guidance Documents. 172 Eastern San Joaquin 2022 GSP, Figure 3-2, p. 295, Figure 4-1, p. 319, Table 4-1, p. 316, Appendix 4- A, pp. 1657-1661.
173 Eastern San Joaquin 2022 GSP, Table 4-3, p. 322.
174 Eastern San Joaquin 2022 GSP, Section 4.7.1, p. 329. 175 Eastern San Joaquin 2022 GSP, Section 2.1.10, p. 160. 176 Eastern San Joaquin 2022 GSP, Section 4.7.5, p. 330. 177 Eastern San Joaquin 2022 GSP, Figure 4-3, p. 331.
178 Eastern San Joaquin 2022 GSP, Section 4.2, p. 322.

The degraded groundwater quality network consists of 31 wells, all of which are also included as part of the broad groundwater level monitoring network. Wells in the groundwater quality network are divided into a representative monitoring well groundwater quality network with 10 wells and a broad groundwater quality network with the remaining 21 wells. The GSP provides maps showing the locations of wells in the representative monitoring well and broad monitoring networks and summarizes well names and construction information in tables.179 The GSP states that the density of the combined groundwater quality network is 2.6 wells per 100 square miles and the representative monitoring well network is 0.8 wells per 100 square miles.180 The GSP describes that the wells in the representative monitoring well and broad networks will be sampled semi-annually for TDS, cations and anions (including nitrate and chloride), arsenic, and various field parameters. 181 Based on the maps, all wells in the representative monitoring well network are located in the western portion of the Subbasin, and the majority of the broad network wells are also located in the western portion of the Subbasin with the exception of two wells located in the northeast. The GSP describes that the representative monitoring well locations were purposefully limited to these western areas where TDS concentrations in groundwater were historically high, or adjacent to these areas to observe potential movement of high TDS groundwater.182 The GSP identifies data gaps in the groundwater quality network including the spatial distribution of wells, well construction data to evaluate depth-discrete groundwater quality, the different monitoring frequencies between different agencies or programs, and the monitoring of additional constituents outside of salinity. 183 In general, some of the proposed monitoring efforts already address some of these data gaps, such as the semiannual monitoring frequency and the monitoring for constituents other than TDS. The GSP also plans to add the 12 new monitoring wells, discussed previously for the groundwater level monitoring network, to the groundwater quality network. Based on the locations of proposed groundwater quality monitoring wells, the spatial distribution of the network should be improved compared to the existing network, but a large groundwater quality monitoring data gap in the central portion of the Subbasin appears to still exist even after the incorporation of the proposed new wells. Department staff believe the proposed groundwater quality network to be insufficient to identify baseline conditions across the Subbasin. Proposed new monitoring wells will fill some of the data gaps in the eastern portion of the Subbasin; however, based on their locations shown on Figure 4-3, there will still be a large groundwater quality data gap in the central portion of the 179 Eastern San Joaquin 2022 GSP, Figure 3-3, p. 303, Figure 4-1, p. 325, Table 4-5, p. 323, Table 4-6, p. 326. 180 Eastern San Joaquin 2022 GSP, Table 4-8, p. 328. 181 Eastern San Joaquin 2022 GSP, Section 4.3, p. 322. 182 Eastern San Joaquin 2022 GSP, Section 4.3.1, p. 323. 183 Eastern San Joaquin 2022 GSP, Section 4.7.2, p. 329.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 45 of 53 Subbasin where the GSP has identified a large groundwater depression. Additionally, it is unclear why the GSP is relying on the construction of new wells to monitor groundwater quality in the eastern portion of the Subbasin, considering existing groundwater level wells have been identified in these areas, and there is likely many other options to monitor groundwater quality from existing agricultural or domestic wells. Department staff recommend that existing wells be evaluated to be included as part of the groundwater quality monitoring network to fill data gaps in the eastern portion of the Subbasin, until newly proposed monitoring wells are constructed. Additionally, Department staff recommend the final groundwater quality network identify a monitoring location in the central portion of the Subbasin where the existing groundwater depression was identified (see Recommended Corrective Action 7).184
The GSP states that the groundwater quality network will be used to evaluate seawater intrusion in the Subbasin through the measurement of chloride concentrations. Seawater intrusion sustainable management criteria is based on a chloride isocontour line that will be developed using data from the groundwater quality network. The GSP is unclear on whether chloride concentrations from both the representative monitoring well and broad groundwater quality networks, or only the representative monitoring well groundwater quality network will be used to develop the isocontour line. Figure 3-4, which displays the chloride isocontour line displays all groundwater quality monitoring wells;185 however, the GSP states “[t]he seawater intrusion monitoring network uses the same monitoring wells and monitoring strategies as the groundwater quality representative monitoring network.

Chloride concentrations will be monitored at the degraded water quality representative monitoring networks wells to develop a chloride isocontour line.”186 Department staff believe that the sole use of the representative monitoring well groundwater quality network (10 wells) is likely insufficient to interpolate the isocontour line as shown, as there do not appear to be enough representative monitoring wells on the western side of the isocontour (see Recommended Corrective Action 8).

As described in the evaluation of Deficiency 2, the GSP proposes to use the representative groundwater level monitoring network as a proxy for land subsidence. The GSP proposes to evaluate other forms of direct land subsidence monitoring data, such as InSAR and CGPS, as available, to identify areas where land subsidence may be occurring and to further evaluate the correlation between land subsidence and groundwater levels. As described in the evaluation of Deficiency 2 and in Recommended Corrective Action 2, Department staff believe that the representative groundwater level monitoring network is insufficient to identify undesirable results from land subsidence, particularly because minimum threshold exceedances are allowed to occur in up to four of 20 representative monitoring wells without being considered an undesirable result. 184 Eastern San Joaquin 2022 GSP, Figure 4-3, p. 331.
185 Eastern San Joaquin 2022 GSP, Figure 3-4, p. 307.
186 Eastern San Joaquin 2022 GSP, Section 4.4, p. 328.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 46 of 53 The GSP proposes to use the representative groundwater level monitoring network to monitor for depletions of interconnected surface water. The GSP also indicates that available stream gauge data will be evaluated to identify potential impacts to beneficial uses and users of surface water; however, the GSP does not identify stream gauge locations. The GSP identifies depletions of interconnected surface water as a data gap and acknowledges that there is a lack of shallow groundwater monitoring wells near the Subbasin’s major rivers and streams. The GSP indicates that new shallow groundwater monitoring wells near streams will be constructed to fill data gaps.187 Department staff believe that as the Agencies address Recommended Corrective Action 6, the monitoring network will also be updated as a result of identifying location, quantity, and timing of stream depletion due to ongoing.

While Department staff have some recommended corrective actions regarding the monitoring networks for seawater intrusion, land subsidence, and depletions of interconnected surface water, in general, the description of the monitoring network included in the Plan substantially complies with the requirements outlined in the GSP Regulations. Overall, the Plan describes in sufficient detail a monitoring network that promotes the collection of data of sufficient quality, frequency, and distribution to characterize groundwater and related surface water conditions in the Subbasin and evaluate changing conditions that occur through Plan implementation. The GSP provides a good explanation for the conclusion that the monitoring network is supported by the best available information and data and is designed to ensure adequate coverage of sustainability indicators. The Plan also describes existing data gaps and the steps that will be taken to fill data gaps and improve the monitoring network. Department staff consider the information presented in the Plan to satisfy the general requirements of the GSP Regulations regarding monitoring network.

5.5 PROJECTS AND MANAGEMENT ACTIONS
The GSP Regulations require a description of the projects and management actions the submitting agency has determined will achieve the sustainability goal for the basin, including projects and management actions to respond to changing conditions in the basin.
188
To achieve the sustainability goal and avoid undesirable results, the GSP proposes projects and management actions in a manner that is consistent and substantially complies with the GSP Regulations.
189
In general, the GSP describes that the management strategy of the Subbasin is to achieve sustainability through the implementation of projects that either offset groundwater use by supplementing with additional surface water supplies or provide additional recharge to the groundwater basin. The GSP identifies some demand conservation projects; 187 Eastern San Joaquin 2022 GSP, Section 4.7.3, p. 329. 188 23 CCR § 354.44 et seq. 189 23 CCR § 354.44 et seq.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 47 of 53 however, they are relatively small in terms of total groundwater offset. The ultimate goal of the projects is to offset the estimated 78,000 acre-feet per year of groundwater recharge or reduced pumping demand needed to reach the sustainable yield estimate.

The GSP presents numerous projects that could be implemented for the Subbasin to reach its sustainable yield estimate. Initially, the GSP presented a list, maps, and descriptions of 23 projects categorized as “Planned”, “Potential”, and “Longer Term or Conceptual”.190 In response to the incomplete determination, the GSAs presented an updated project list that grouped projects into Category A or Category B projects. The updated list presented 26 total projects with 11 Category A projects – considered to be projects that are likely to be implemented within the next five years and have existing water rights, and 15 Category B projects – considered to be projects that will not be implemented in the next five years, but could be pursued if additional groundwater offset is needed to reach sustainability and the projects appear feasible after additional planning and studies are conducted.191 In addition to the updated project list, the GSP included updated modeling scenarios that estimate the effects of Category A projects on the projected future water budget. Based on the modeling results, implementing all Category A projects will result in an average annual groundwater storage surplus for the Subbasin of 5,300 acre-feet per year in the projected groundwater budget without climate change. 192 However, with climate change considered, modeling results indicate an average annual groundwater storage deficit of 15,700 acre-feet per year, even with the implementation of all Category A projects. 193 Based on these results, the GSP acknowledges that additional projects of management actions may be needed to reach the sustainable yield estimate.

The GSP indicates that there are currently no plans for groundwater demand management actions; however, the GSP states that GSAs may implement management actions in the future should conditions warrant. 194 The GSP describes existing conservation or demand management actions that have been in place prior to GSP development through various Urban Water Management Plans and Agricultural Water Management Plans in the Subbasin.195 Additionally, the GSP describes various adaptive management strategies that may be considered if it appears that Subbasin’s proposed projects are not enough on their own for the Subbasin to reach sustainability. These potential adaptive management strategies include groundwater extraction fees, rotational or permanent fallowing of crop lands, conservation programming for demand reduction, and mandatory demand reduction.196
190 Eastern San Joaquin 2022 GSP, Section 6.1, pp. 341-376. 191 Eastern San Joaquin 2022 GSP, Section 6.5, pp. 380-385. 192 Eastern San Joaquin 2022 GSP, Section 2.3.7.6.2, p. 276. 193 Eastern San Joaquin 2022 GSP, Section 2.3.7.7.2, p. 281. 194 Eastern San Joaquin 2022 GSP, Section 6.3, p. 376.
195 Eastern San Joaquin 2022 GSP, Section 6.3, pp. 377-378. 196 Eastern San Joaquin 2022 GSP, Section 6.4, pp. 378-379.

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GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 48 of 53 The Plan adequately describes proposed projects and management actions in a manner that is generally consistent and substantially complies with the GSP Regulations.197 The projects and management actions, which focus largely on projects that offset groundwater use with additional surface water supplies or projects that increase groundwater recharge, are directly related to the sustainable management criteria and present a generally feasible approach to achieving the sustainability goal of the Subbasin.

As projects and management actions are implemented, the Department expects that progress be included in annual reports and any addition or removal of project and management actions be documented in future periodic evaluations.

5.6 CONSIDERATION OF ADJACENT BASINS/SUBBASINS
SGMA requires the Department to “…evaluate whether a groundwater sustainability plan adversely affects the ability of an adjacent basin to implement their groundwater sustainability plan or impedes achievement of sustainability goals in an adjacent basin.”198 Furthermore, the GSP Regulations state that minimum thresholds defined in each GSP be designed to avoid causing undesirable results in adjacent basins or affecting the ability of adjacent basins to achieve sustainability goals.199
The Eastern San Joaquin Subbasin has seven adjacent subbasins, the Delta Mendota, Consumnes, East Contra Costa, Modesto, Solano, South American, and Tracy subbasins. All adjacent Subbasins are high and medium priority subbasins, which are currently required to be managed under a GSP.

The Plan does not include a discussion of its potential impacts to the adjacent subbasins; however, the GSP does indicate that various inter-basin coordination meetings have taken place with the Consumnes, Tracy, Modesto, South American, Solano, and East Contra Costa subbasins. Of these subbasins, Eastern San Joaquin is the only critically overdrafted basin, thus, at the time of GSP development, these meetings mainly discussed elements of the Eastern San Joaquin GSP, and efforts to coordinate in the future.200 While potential impacts to adjacent subbasins are not discussed, the GSP’s water budget estimates include subsurface outflows and inflows between adjacent basins. 201 A public comment from the Sacramento County GSA, on behalf of the Consumnes Subbasin, encourages increased coordination for future subsurface flow estimates related to the water budgets, addressing data gaps related to surface water / groundwater interaction along Dry Creek, and potentially re-evaluating the minimum threshold for representative monitoring well 04N07E20H003 to reduce the potential for subsurface flow from the Consumnes to the Eastern San Joaquin Subbasin. No additional comments relating to impacts to adjacent basins were received by the Department. 197 23 CCR §§ 354.44 et seq. 198 Water Code § 10733(c). 199 23 CCR § 354.28(b)(3).
200 Eastern San Joaquin 2022 GSP, Section 1.3.5, p. 94. 201 Eastern San Joaquin 2022 GSP, Section 2.3.5, p. 230.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 49 of 53 Based on information available at this time, Department staff have no reason to believe that groundwater management in the Eastern San Joaquin Subbasin will adversely affect groundwater conditions in the adjacent subbasins at this time. Department staff will continue to review periodic evaluations to the Plan to assess whether implementation of the Eastern San Joaquin Subbasin Groundwater Sustainability Plan is potentially impacting adjacent basins.

5.7 CONSIDERATION OF CLIMATE CHANGE AND FUTURE CONDITIONS The GSP Regulations require a GSA to consider future conditions and project how future water use may change due to multiple factors including climate change.202 Since the original GSP was adopted and submitted in 2020, climate change conditions have advanced faster and more dramatically. It is anticipated that the hotter, dryer conditions will result in a loss of 10 percent of California’s water supply. As California adapts to a hotter, drier climate, GSAs should be preparing for these changing conditions as they work to sustainably manage groundwater within their jurisdictional areas.

Specifically, the Department encourages GSAs to explore how the proposed groundwater level thresholds have been established in consideration of groundwater level conditions in the basin based on current and future drought conditions. The Department encourages GSAs to also explore how groundwater level data from the existing monitoring network will be used to make progress towards sustainable management of the basin given increasing aridification and effects of climate change, such as prolonged drought. Lastly, the Department encourages GSAs to continually coordinate with the appropriate groundwater users, including but not limited to domestic well owners and state small water systems, and the appropriate overlying county jurisdictions developing drought plans and establishing local drought task forces 203 to evaluate how the Agency’s groundwater management strategy aligns with drought planning, response, and mitigation efforts within the basin.
202 23 CCR § 354.18.
203 Water Code § 10609.50.

ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 50 of 53 6 STAFF RECOMMENDATION
Department staff believe sufficient action has been taken by the GSAs to the deficiencies identified. Department staff recommend APPROVAL of the 2022 Plan with the recommended corrective actions listed below. The Plan conforms with Water Code Sections 10727.2 and 10727.4 of SGMA and substantially complies with the GSP Regulations. Implementation of the Plan will likely achieve the sustainability goal for the Eastern San Joaquin Subbasin. The GSAs have identified several areas for improvement of its Plan and Department staff concur that those items are important and should be addressed as soon as possible. Department staff have identified recommended corrective actions that should be considered by the GSAs for the first periodic evaluation of its GSP.

Addressing these recommended corrective actions will be important to demonstrate that implementation of the Plan is likely to achieve the sustainability goal. The recommended corrective actions include:

RECOMMENDED CORRECTIVE ACTION 1
The GSP does not provide a sufficient evaluation of the potential impacts to various beneficial uses and users of groundwater related to the chronic lowering of groundwater level minimum thresholds and criteria used to identify undesirable results. The following items should be addressed:
1a.Department staff recommend the Agencies explain the selection of 25 percent of exceedances as considered undesirable, including details describing the groundwater conditions and how those conditions constitute a significant and unreasonable effect of beneficial uses and users.

Department staff also recommend that the updated modeling results be used to quantify and disclose the potential impacts to groundwater well users during projected conditions where minimum thresholds are exceeded but undesirable results do not occur. In addition to impacts to domestic and municipal wells, this evaluation should include impacts to smaller water systems reliant on groundwater wells. Department staff also recommend that the GSAs review the Department’s April 2023 guidance document titled Considerations for Identifying and Addressing Drinking Water Well Impacts guidance to assist its adaptive management efforts. 1b. Department staff recommend the GSP include a more thorough evaluation of the impacts to environmental uses and users related to the groundwater level minimum thresholds, or, at minimum, describe a plan to perform this evaluation in the future when additional data become available.
1c. The GSP should evaluate the minimum thresholds in relation to the depths of nearby public water systems and state small water systems reliant on groundwater wells. While it may be reasonable to assume that wells in these systems are generally deeper than domestic wells, which were part of the minimum threshold ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 51 of 53 analysis, Department staff recommend that an evaluation of these smaller water systems be disclosed by the GSP.
1d.Department staff recommend the Agencies develop a more detailed plan describing how the assessment of groundwater quality in relation to declining groundwater levels will be conducted, including identifying specific analyses, well locations (either wells already monitored as part of GSP implementation or wells monitored by other programs), sampling frequency, and data gaps.

RECOMMENDED CORRECTIVE ACTION 2
Until a correlation between groundwater levels and land subsidence is established, the GSP should use direct subsidence monitoring data, such as InSAR or CGPS, to define sustainable management criteria (minimum thresholds and undesirable results). In general, the Agencies describe that land subsidence has never been a problem in the Subbasin and imply that land subsidence should not be a problem in the future. If this is accurate, setting land subsidence minimum thresholds using direct monitoring data should not trigger undesirable results and would also be the easiest pathway to developing sustainable management criteria for land subsidence, since a correlation between groundwater levels and land subsidence would no longer need to be established.

Department staff recommend Agencies clearly describe how potential subsidence associated with groundwater level declines below minimum thresholds would not have the potential to cause significant and unreasonable impacts and undesirable results to related to subsidence and the use of InSAR data for the land subsidence monitoring network, with supplemental groundwater level data being utilized to evaluate whether detected land subsidence is the result of declining groundwater levels. The use of InSAR data is also recommended for use in establishing a rate and extent in defining significant and unreasonable impacts considered not to cause undesirable results to the Subbasin.

RECOMMENDED CORRECTIVE ACTION 3
Department staff recommend that in the first periodic evaluation of the GSP, only water budgets developed from the most recent or best available data be included. As currently presented, it is unclear whether the sustainable yield estimate and estimated groundwater offset required to achieve sustainability are based on the updated modeling results (based on ESJWRM Version 2.0) or are from the modeling scenarios presented in the original GSP submitted in 2020 (based on ESJWRM Version 1.0).

RECOMMENDED CORRECTIVE ACTION 4
Department staff recommend the GSP provide a revised estimate for the reduction of groundwater storage volume that is considered an undesirable result. Alternatively, the GSP could highlight how the maximum reduction of groundwater storage related to the ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 52 of 53 chronic lowering of groundwater level minimum thresholds would not result in significant and unreasonable impacts related to groundwater storage and omit the 23 MAF estimate.

RECOMMENDED CORRECTIVE ACTION 5
Department staff recommend the GSP provide additional explanation for how the 2,000 mg/L chloride isocontour line will prevent significant and unreasonable impacts to beneficial uses and users of groundwater. Additionally, the Plan should provide the current chloride conditions and interim milestones for seawater intrusion.

RECOMMENDED CORRECTIVE ACTION 6
Department staff understand that estimating the location, quantity, and timing of stream depletion due to ongoing, Subbasin-wide pumping is a complex task and that developing suitable tools may take additional time; however, it is critical for the Department’s ongoing and future evaluations of whether GSP implementation is on track to achieve sustainable groundwater management. The Department plans to provide guidance on methods and approaches to evaluate the rate, timing, and volume of depletions of interconnected surface water and support for establishing specific sustainable management criteria in the near future. This guidance is intended to assist GSAs to sustainably manage depletions of interconnected surface water.

In addition, the GSA should work to address the following items by the first periodic evaluation:
a. Work to establish undesirable results, minimum thresholds, and measurable objectives consistent with the GSP Regulations. Measurable objectives are to use the same metric used for minimum thresholds, including quantifying the location, quantity, and timing of depletions of interconnected surface water due to groundwater extraction. Consider utilizing the interconnected surface water guidance, as appropriate, when issued by the Department. b. Continue to fill data gaps, collect additional monitoring data, and implement the current strategy to manage depletions of interconnected surface water and define segments of interconnectivity and timing. The monitoring network should be updated to reflect any corresponding changes and approaches. c. Prioritize collaborating and coordinating with local, state, and federal regulatory agencies as well as interested parties to better understand the full suite of beneficial uses and users that may be impacted by pumping induced surface water depletion within the GSA’s jurisdictional area.

RECOMMENDED CORRECTIVE ACTION 7
Department staff recommend that existing wells be evaluated to be included as part of the groundwater quality monitoring network to fill data gaps in the eastern portion of the ATTACHMENT 2
GSP Assessment Staff Report July 6, 2023
San Joaquin Valley – Eastern San Joaquin Subbasin (No. 5-022.01) California Department of Water Resources
Sustainable Groundwater Management Program Page 53 of 53 Subbasin, until newly proposed monitoring wells are constructed. Additionally, Department staff recommend the final groundwater quality network identify a monitoring location in the central portion of the Subbasin where the existing groundwater depression was identified.

RECOMMENDED CORRECTIVE ACTION 8
The GSP currently states that only groundwater quality wells from the representative monitoring network will be utilized to create the chloride isocontour line that will be used to evaluate seawater intrusion sustainable management criteria. As currently depicted, very few representative monitoring wells are on the western side of the isocontour line.

Department staff recommend that development of the chloride isocontour line utilize all groundwater quality wells in the western portion of the Subbasin, as appropriate considering well construction information.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 1 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 TECHNICAL MEMORANDUM NO. 1 – Groundwater Levels
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Ashley Couch, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Emily Honn and Nicole Koerth, Woodard & Curran DATE: November 2024
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s July 6, 2023 Approved Determination Letter for the 2022 Revised GSP - Technical Memorandum No. 1, Response to DWR Recommended Corrective Action No. 1
On July 27, 2022, the Groundwater Sustainability Agencies (GSAs) submitted the Eastern San Joaquin Groundwater Subbasin Revised 2022 Groundwater Sustainability Plan (GSP or Plan) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) to the California Department of Water Resources (DWR) in response to DWR’s incomplete determination letter dated January 28, 2022. In a July 6, 2023 letter, DWR staff concluded that the GSAs had taken sufficient actions to correct deficiencies identified by DWR and approved the 2022 Revised Plan (see Appendix 3-B of the GSP). In Section 6 of the letter, DWR staff also identified recommended corrective actions (RCAs) for the GSAs to address by the Plan’s first periodic evaluation.

This technical memorandum (TM) is in response to RCA #1 related to groundwater levels. This TM is organized into the following sections:
1) Overview of Recommended Corrective Action #1
2) Approach to Recommended Corrective Action #1
3) Update to Groundwater Level Minimum Thresholds
4) Impacts Analysis
5) Plan for Future Assessment of Degraded Groundwater Quality related to Groundwater Levels 6) Conclusions
7) References
ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 2 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024

1. OVERVIEW OF RECOMMENDED CORRECTIVE ACTION #1
The following was the text included in Section 6 of DWR’s July 2023 Determination Letter:

The GSP does not provide a sufficient evaluation of the potential impacts to various beneficial uses and users of groundwater related to the chronic lowering of groundwater level minimum thresholds and criteria used to identify undesirable results. The following items should be addressed:
• 1a. Department staff recommend the Agencies explain the selection of 25 percent of exceedances as considered undesirable, including details describing the groundwater conditions and how those conditions constitute a significant and unreasonable effect of beneficial uses and users.

Department staff also recommend that the updated modeling results be used to quantify and disclose the potential impacts to groundwater well users during projected conditions where minimum thresholds are exceeded but undesirable results do not occur. In addition to impacts to domestic and municipal wells, this evaluation should include impacts to smaller water systems reliant on groundwater wells. Department staff also recommend that the GSAs review the Department’s April 2023 guidance document titled Considerations for Identifying and Addressing Drinking Water Well Impacts guidance to assist its adaptive management efforts. • 1b. Department staff recommend the GSP include a more thorough evaluation of the impacts to environmental uses and users related to the groundwater level minimum thresholds, or, at minimum, describe a plan to perform this evaluation in the future when additional data become available. • 1c. The GSP should evaluate the minimum thresholds in relation to the depths of nearby public water systems and state small water systems reliant on groundwater wells. While it may be reasonable to assume that wells in these systems are generally deeper than domestic wells, which were part of the minimum threshold analysis, Department staff recommend that an evaluation of these smaller water systems be disclosed by the GSP.
• 1d. Department staff recommend the Agencies develop a more detailed plan describing how the assessment of groundwater quality in relation to declining groundwater levels will be conducted, including identifying specific analyses, well locations (either wells already monitored as part of GSP implementation or wells monitored by other programs), sampling frequency, and data gaps.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 3 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024

2. APPROACH TO RECOMMENDED CORRECTIVE ACTION #1
In response to RCA #1, a comprehensive evaluation of impacts to the beneficial users of groundwater in the Eastern San Joaquin Subbasin (Subbasin) as a result of the established groundwater level sustainable management criteria (SMC) was completed for the 2025 Periodic Evaluation of the Subbasin’s GSP and for inclusion in a GSP amendment (2024 Amended GSP). Impacts on the following beneficial users were incorporated into the revised analyses to address RCA #1a-c:
• Domestic Wells (included in the original (2020) GSP, and amended (2024) GSP) • Groundwater Dependent Ecosystems (GDEs)
• Public Water Systems and Community Water Systems
Impacts to wells that public water systems, and specifically small community water systems, rely on were assessed in a manner similar to that used for domestic wells in the 2020 GSP (RMC #1c, Section 4.1). Impacts to potential GDEs were preliminarily evaluated in a manner similar to that used for public water systems and domestic wells (RCA #1b, Section Error! Reference source not found.). These updated well and potential GDE impacts analyses were then evaluated across a range of undesirable result definitions in order to provide more context and support for why the threshold in the 2020 GSP is considered reasonable (RCA #1a, Section 4.2).

Lastly, a plan was developed to evaluate the relationship between declining groundwater levels and degrading water quality, long-term (RCA #1d, Section 5). Analysis of water quality data in the Subbasin is included in more detail in the Groundwater Quality TM (TM No. 3), but the portion relevant to addressing RCA #1d is included in Section 0 of this TM.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 4 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024

3. UPDATE TO GROUNDWATER LEVEL MINIMUM THRESHOLDS
The groundwater level minimum thresholds (MTs) in the 2020 GSP were calculated as the shallower of the following:
• 1992, 2015, or 2016 groundwater level low + buffer equal to 100% of historical range • 10th percentile of domestic well depths within a 3-mile radius1 To be more consistent with the requirements and expectations expressed by DWR, the new groundwater level minimum thresholds were adjusted during the Periodic Evaluation and subsequent GSP Amendment to be calculated as the shallower of the following:
• 2015 groundwater level low + buffer equal to 100% of historical range • 10th percentile of domestic well depths within a 3-mile radius2 Table 1 shows the current wells that make up the representative monitoring network (RMN) for groundwater levels with the minimum thresholds established in the 2020 GSP, how they were initially calculated, the revised minimum thresholds, and how they were calculated in the 2024 Amended GSP.

Figure 1 shows where these wells are located within the Subbasin.

With this change, the minimum threshold was increased (raised) at six wells, resulting in a more protective minimum threshold than was established in the 2020 GSP for the same wells. These six wells averaged a

7.6-foot increase in their minimum threshold values. This change also resulted in a lower minimum threshold at three wells, by an average of approximately 1.7 feet. Overall, the new minimum thresholds are more protective of beneficial uses within the Subbasin.

Additionally, two new multi-completion wells have been added to the RMN for groundwater levels: SEWD01 and NSJWCD-01. These wells were recently constructed under DWR’s Technical Support Services (TSS) program. Table 2 summarizes the construction information for the new monitoring wells. These wells will be monitored starting in WY 2025. SEWD-01 contains two boreholes: the deeper one has two completions and the shallower one has three. NSJWCD-01 also contains two boreholes: the shallower one has four completions and the deeper one has two.

These new wells fill a data gap; however, there are insufficient groundwater level observations to establish sustainable management criteria (SMCs) for these new wells. Bi-annual collection of groundwater levels at these sites will continue to fill the data gap. SMCs will be established at these representative monitoring sites after at least four years of data have been collected, including data for at least one wet year and one dry or critical year during that time period. If wet and dry/critical years do not occur during this initial period, then additional years of data collection may be required before establishing SMCs. 1 One well is analyzed using a 2-mile radius
2 One well is still analyzed using a 2-mile radius
ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 5 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Minimum thresholds for these and other new wells that may be constructed in the future will be established based on adjusted recent groundwater levels from a dry/critical year. The adjustment of groundwater levels is the difference in simulated groundwater levels in ESJWRM between Water Year 2015 (a dry year) and the recent dry/critical year when groundwater level observations are measured. The calculation for the minimum threshold is:

𝑀𝑖𝑛𝑖𝑚𝑢𝑚 𝑇ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑
= 𝑂𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑅𝑒𝑐𝑒𝑛𝑡 𝐷𝑟𝑦/𝐶𝑟𝑖𝑡𝑖𝑐𝑎𝑙 𝐺𝑊𝐿 − (𝑆𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 𝑅𝑒𝑐𝑒𝑛𝑡 𝐷𝑟𝑦 𝑌𝑒𝑎𝑟 𝐺𝑊𝐿𝑠 − 𝑆𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 2015 𝐺𝑊𝐿𝑠)
As a hypothetical example, suppose Water Year 2027 is a critical year and the observed groundwater elevation for Well A is 75 feet mean sea level (msl) in 2027. Assuming that the simulated groundwater elevations in ESJWRM at Well A increase by 8 feet between 2015 and 2027. The minimum threshold would be 75 feet minus 8 feet, or 67 feet msl.

Conversely, measurable objectives will be established from an adjustment in groundwater levels from a wet year. The adjustment will add the difference in simulated groundwater levels from ESJWRM between Water Year 2011 (a wet year) and a recent wet year when groundwater level observations are collected. The calculation for measurable objectives is:

𝑀𝑒𝑎𝑠𝑢𝑟𝑎𝑏𝑙𝑒 𝑂𝑏𝑗𝑒𝑐𝑡𝑖𝑣𝑒𝑠
= 𝑂𝑏𝑠𝑒𝑟𝑣𝑒𝑑 𝑅𝑒𝑐𝑒𝑛𝑡 𝑊𝑒𝑡 𝐺𝑊𝐿 + (𝑆𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 𝑅𝑒𝑐𝑒𝑛𝑡 𝑊𝑒𝑡 𝑌𝑒𝑎𝑟 𝐺𝑊𝐿 − 𝑆𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 2011 𝐺𝑊𝐿𝑠)
As a hypothetical example, suppose Water Year 2026 is a wet year, and the observed groundwater elevation for Well A is 82 feet msl that year. Suppose that the simulated groundwater elevations in ESJWRM at Well A decrease by 15 feet between Water Year 2011 and 2026. The measurable objective would be 82 feet minus negative 15 feet, equaling 97 feet msl.

In the absence of historical data, this methodology is meant to estimate historical conditions as closely as possible.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 6 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Table 1: Updated Minimum Thresholds for Groundwater Levels CASGEM Well ID Local Well ID Original
GSP
Minimum
Threshold
(ft MSL)
Original
GSP
Minimum
Threshold
Source
2025 GSP
Minimum
Threshold
(ft MSL)
2025 GSP
Minimum
Threshold
Source
378824N1210000W001 01S09E05H002 -49.8 Dom well
depth
-49.8 Dom well
depth
379316N1211665W001 01N07E14J002 -114.4 GWL -93.9 GWL
380067N1213458W003 Swenson-3 -26.6 GWL -26.6 GWL
380206N1210943W001 02N08E15M002 -124.1 Dom well
depth
-124.1 Dom well
depth
Not in CASGEM #3 Bear Creek -72.3 GWL -73.8 GWL
Not in CASGEM Lodi City Well #2 -38.5 GWL -34.4 GWL
Not in CASGEM Manteca 18 -16.0 GWL -19.0 GWL
381843N1212261W001 04N07E20H003M -81.7 GWL -80.5 GWL
380909N1212153W001 03N07E21L003 -100.0 GWL -94.0 GWL
Not in CASGEM Hirschfeld (OID-8) 8.0 GWL 7.9 GWL
377909N1208675W001 Burnett (OID-4) 60.7 GWL 60.8 GWL
377136N1212508W001 02S07E31N001 1.5 GWL 0.8 GWL
377810N1211142W001 02S08E08A001 0.6 GWL 0.6 GWL
380578N1212017W001 02N07E03D001 -122.8 Dom well
depth
-113.7 GWL
379661N1210011W001 01N09E05J001 -86.8 Dom well
depth
-86.8 Dom well
depth
379976N1212308W001 02N07E29B001 -130.1 Dom well
depth
-130.1 Dom well
depth
381559N1213727W001 04N05E36H003 -31.1 GWL -31.1 GWL
381317N1213524W001 03N06E05N003 -35.1 GWL -35.1 GWL
381816N1213723W001 04N05E24J004 -31.2 GWL -31.2 GWL
378163N1208321W001 01S10E26J001M 43.7 GWL 43.7 GWL
378846N1208816W001 01S10E04C001M 50.0 GWL 54.7 GWL
382345N1212261W001 -
06 NSJWCD-01
- -

NA NA TBD TBD
379794N1211083W001 -
05 SEWD-01 NA NA TBD TBD
ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 7 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Table 2: New Wells to be Added to the GWL Representative Monitoring Network Well Name Well Depth/Planned Well
Depth (ft below ground
surface)
Description
SEWD-01 SEWD-01-A (North): 165
SEWD-01-B (North): 405
SEWD-01-C (South): 580
SEWD-01-D (South): 900
SEWD-01-E (South): 1,200
• TSS Well within Stockton
East Water District GSA
• Drilled and developed in
2021
NSJWCD-01 NSJWCD-01-A (Shallow): 190
NSJWCD-01-B (Shallow): 360
NSJWCD-01-C (Shallow): 590
NSJWCD-01-D (Shallow): 780
NSJWCD-01-E (Deep): 1,250
NSJWCD-01-F (Deep): 1,635
• TSS Well within North San
Joaquin Water Conservation
District
• Drilled in 2020, developed in
2021
ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 8 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 1: Representative Monitoring Network for Groundwater Levels ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 9 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024

4. IMPACTS ANALYSIS

4.1 Well Impacts Analysis Methods
An inventory of all wells within the Eastern San Joaquin Subbasin was compiled by their use, type, and depth. This list was then filtered by the following attributes:
• Only active wells.
• Well depths are known.
• Only wells drilled after 1974 (in order to only consider wells that are within their usable lifespan, assumed to be approximately 50 years)
The remaining wells were then sorted into each of the following type categories:
• Domestic wells
• Public Supply Wells
• Public Supply Wells that are within a Community Water System (CWS) State small water systems are defined as systems that serve 5 to 14 service connections and do not regularly serve drinking water to more than an average of 25 individuals daily for more than 60 days out of the year (California State Water Resources Control Board, 2021). State small water systems have fewer connections and serve fewer permanent residents than community water systems (CWS). However, since the location and depth of wells that state small water systems rely on is not readily available, this analysis conservatively looks more broadly at what wells are within CWS service areas within the Subbasin. It is assumed that if there are impacts to CWS, then there likely will be impacts to state small water systems.

A 3-mile radius around each monitoring location was delineated to represent an “Impact Zone” of that representative monitoring well (RMW). For simplicity and to be most conservative, it was assumed that groundwater levels, and therefore their impact, are uniform within the Impact Zone. For example, in this analysis, a domestic well that is 2 miles away from the RMW location is assumed to be impacted to the same degree as a well that is 0.5 miles away. Table 3 shows the total number of wells, by type, within each RMW’s Impact Zone. The range in well depths, as well as the average well depth, are also shown by type.

Figure 2 and Figure 3 show the impact zones for each RMW for domestic wells and public supply wells, respectively. These impact zones are shown overlying the inventory of wells that meet the above criteria for each well group. Figure 4 shows the same, but with public supply wells that are within a CWS.

The depth of the 10th percentile well depth was determined for all wells within the Impact Zone for each well type. This threshold represents the depth at which 90% of the wells would be deeper within each Impact Zone. This is consistent with how the domestic well impacts component of the minimum threshold calculation was completed in the 2020 GSP, but is now applied to domestic wells, public supply wells, and public supply wells that fall within a CWS. The 10th percentile depth for each well type was then compared to the lowest groundwater level observed in 2015 plus a buffer of 100% of the historical range, or the minimum threshold at wells ”assumed” to drop to their minimum threshold. The 2015 low groundwater elevation is considered to be the worst-case scenario in this analysis and therefore the results represent the most conservative assumptions.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 10 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Table 3: Well Detail for Impacts Analysis, by Type
Well Type Total Number
within 3-mile
Radius Impact
Zone of RMWs
Well Depth
Range
within 3-mile
Radius Impact
Zone of
RMWs
(ft bgs)
Well Depth
Average
within 3-mile
Radius Impact
Zone of
RMWs
(ft bgs)
Domestic Wells 4,855 5 to 1300 248
Public Supply Wells 165 72 to 856 357
Public Supply Wells –
Community Water System
58 72 to 720 382
ft bgs = feet below the ground surface
ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 11 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 2: Inventory of Domestic Wells with Identified Impact Zones around each RMW ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 12 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 3: Inventory of Public Supply Wells with Identified Impact Zones around each RMW ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 13 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 4: Inventory of Public Supply within a Community Water System (CWS) with Identified Impact Zones around each RMW

4.2 Well Impacts Analysis Results
The impacts analysis completed for domestic wells, public supply wells, and groundwater dependent ecosystems was evaluated across a range of different definitions of undesirable results. The GSP defined the undesirable result for groundwater levels to be:

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 14 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Undesirable Result = 25% of the 20 Representative Monitoring Network Wells drop to their minimum threshold for 2 consecutive years1
A series of scenarios were assessed based on different definitions of what the undesirable result represents.

Specifically, the different undesirable result scenarios that were evaluated assumed, of the 21 RMWs for groundwater levels from the 2022 GSP:
• 10 wells drop to their minimum threshold, representing 48% of the RMWs. • 8 wells drop to their minimum threshold, representing 38% of the RMWs. • 5 wells drop to their minimum threshold, representing 24% of the RMWs2. • 3 wells drop to their minimum threshold, representing 14% of the RMWs.

This analysis conservatively only considered the impacts from a single year of undesirable results, rather than two consecutive years.

Table 4 through Error! Reference source not found. show the results of the impacts analysis described in the previous sections, reported by representative monitoring network well. Table 4 through Table 6 presents the results of the well impacts analysis; Table 4 for domestic wells, Table 5 for public supply wells, and Table 6 for public supply wells in community water systems. The number of wells of each type that may go dry is shown for each scenario. A well within each Impact Zone is considered to go dry if the groundwater level at the representative monitoring network well drops below the total completion depth of the well.

In each scenario, the wells that have groundwater levels drop to their minimum threshold were selected based on how close their 2015 low groundwater level was to the minimum threshold. For example, a representative network well with a groundwater level 1 ft away from the minimum threshold would be selected over a well that has groundwater levels 10 ft over its minimum threshold. In each scenario, the number of wells with groundwater levels that are assumed to drop to their minimum threshold represent the 10 closest wells to their minimum threshold.

The total number of wells shown in the second column indicates the number of wells within each representative network well radius that is of that particular well type. Columns 3 through 6 represent the number of those wells that are shallower than the groundwater level or the minimum threshold, if that is a well that was selected for use in the simulation.
1 There was an additional well added to the RMN for groundwater levels in 2021. Two more wells are being added in the 2024 GSP, as described in Section 3 of this document. The minimum thresholds for these wells will be established in a future GSP.
2 Note: The 2020 GSP had 20 RMWs, and therefore five wells resulted in an undesirable result definition of 25%. For the purposes of comparison, the same five wells are used, but the percentage is reported as 5/21 = approximately 24% in this study.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 15 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Two additional evaluation radii or rings were added to the analysis to ensure that impacts in sensitive areas are being incorporated beyond the RMWs: Along the San Joaquin River and in the Bay Delta area. The centroid of these additional radii is not an actual well location and serves for a hypothetical comparison to understand what the impacts in those areas may be using the same approach. The groundwater level used at these additional rings is the lowest simulated by ESJWRM in 2015. Since the rings are not centered around an actual well, there are no observed groundwater levels at these two locations.

Table 4 through Table 6 indicate that in all undesirable result scenarios, less than 2% of wells of each type may go dry. An undesirable result where groundwater levels in 48% of RMWs reach their MTs represents the largest impact to both domestic wells and public supply wells, with a declining percentage of impact to domestic and public supply wells with each less protective scenario (where fewer RMWs exceed their MTs).

For community water systems, the impact is the same in all scenarios, with 1 out of 58 total CWS wells impacted. Further investigation would be required to assess whether this single impacted well is a well that is relied upon by a state small water system. At the current undesirable result definition, <1% of domestic and public supply wells and <2% of community water system wells are estimated to go dry. Even if 10 RMWs were to drop to their minimum threshold, it is estimated that < 2% of domestic and/or public supply wells would go dry.

ATTACHMENT 2
2024 Amended Groundwater Sustainability Plan 16 Woodard & Curran, Inc.

Technical Memorandum No. 1: Groundwater Levels November 2024 Table 4: Impacts on Domestic Wells under Various Undesirable Results Scenarios

DOMESTIC WELLS
Number of Rep MN Wells at MT:
10 8 5 3
% of Rep MN Wells at MT:
48% 38% 24% 14%
Total Number of Wells Within
Radius Number of Dry Domestic Wells
01S09E05H002 139 2 1 1 1
01N07E14J002 120 0 0 0 0
Swenson-3 62 0 0 0 0
02N08E15M002 144 2 2 2 2
#3 Bear Creek 165 0 0 0 0
Lodi City Well #2 196 3 0 0 0
Manteca 18 328 5 5 2 2
04N07E20H003M 321 0 0 0 0
03N07E21L003 121 0 0 0 0
Hirschfeld (OID-8) 524 7 7 7 7
Burnett (OID-4) 479 10 10 4 4
02S07E31N001 175 2 2 2 1
02S08E08A001 303 6 6 6 2
02N07E03D001 363 0 0 0 0
01N09E05J001 162 0 0 0 0
02N07E29B001 627 1 1 1 1
04N05E36H003 97 0 0 0 0
03N06E05N003 142 3 3 1 1
04N05E24J004 74 0 0 0 0
01S10E26J001M 268 2 2 2 2
01S10E04C001M 45 0 0 0 0
Additional Ring at River 286 1 1 1 1
Additional Ring at Delta 10 0 0 0 0
TOTALS (Within Rep MN Radii) 4855 43 39 28 23
% of Domestic Wells Dry (Within
Rep MN Radii) 0.9% 0.8% 0.6% 0.5%
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Technical Memorandum No. 1: Groundwater Levels November 2024 Table 5: Impacts on Public Supply Wells under Various Undesirable Results Scenarios

PUBLIC SUPPLY WELLS
Number of Rep MN
Wells at MT: 10 8 5 3
% of Rep MN Wells at
MT:
48% 38% 24% 14%
Total Number of Wells
Within Radius Number of Dry Public Supply Wells
01S09E05H002 0 0 0 0 0
01N07E14J002 5 0 0 0 0
Swenson-3 7 0 0 0 0
02N08E15M002 2 0 0 0 0
#3 Bear Creek 4 0 0 0 0
Lodi City Well #2 28 1 0 0 0
Manteca 18 17 0 0 0 0
04N07E20H003M 8 0 0 0 0
03N07E21L003 4 0 0 0 0
Hirschfeld (OID-8) 5 0 0 0 0
Burnett (OID-4) 5 0 0 0 0
02S07E31N001 2 0 0 0 0
02S08E08A001 11 0 0 0 0
02N07E03D001 11 0 0 0 0
01N09E05J001 3 0 0 0 0
02N07E29B001 24 1 1 1 1
04N05E36H003 9 0 0 0 0
03N06E05N003 13 0 0 0 0
04N05E24J004 4 0 0 0 0
01S10E26J001M 3 0 0 0 0
01S10E04C001M 0 0 0 0 0
Additional Ring at River 15 0 0 0 0
Additional Ring at Delta 1 0 0 0 0
TOTALS (Within Rep MN Radii) 165 2 1 1 1
% of Public Supply Wells
Dry (Within Rep MN
Radii)

1.2% 0.6% 0.6% 0.6%
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Technical Memorandum No. 1: Groundwater Levels November 2024 Table 6: Impacts on Public Supply Wells in Community Water Systems under Various Undesirable Results Scenarios

COMMUNITY WATER SYSTEM WELLS
Number of Rep MN Wells at MT:
10 8 5 3
% of Rep MN Wells at MT:
48% 38% 24% 14%
Total Number of Wells Within Radius Number of Dry CWS Wells 01S09E05H002 0 0 0 0 0
01N07E14J002 0 0 0 0 0
Swenson-3 7 0 0 0 0
02N08E15M002 1 0 0 0 0
#3 Bear Creek 2 0 0 0 0
Lodi City Well #2 15 1 0 0 0
Manteca 18 13 0 0 0 0
04N07E20H003M 1 0 0 0 0
03N07E21L003 0 0 0 0 0
Hirschfeld (OID-8) 0 0 0 0 0
Burnett (OID-4) 2 0 0 0 0
02S07E31N001 0 0 0 0 0
02S08E08A001 4 0 0 0 0
02N07E03D001 3 0 0 0 0
01N09E05J001 3 0 0 0 0
02N07E29B001 3 0 1 1 1
04N05E36H003 0 0 0 0 0
03N06E05N003 3 0 0 0 0
04N05E24J004 0 0 0 0 0
01S10E26J001M 1 0 0 0 0
01S10E04C001M 0 0 0 0 0
Additional Ring at River 5 0 0 0 0
Additional Ring at Delta 0 0 0 0 0
TOTALS (Within Rep MN Radii) 58 1 1 1 1
% of CWS Wells Dry (Within Rep MN
Radii) 1.7% 1.7% 1.7% 1.7%
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Technical Memorandum No. 1: Groundwater Levels November 2024

4.3 Potential GDE Impacts Analysis Methods
In the Eastern San Joaquin Subbasin, the primary environmental beneficial users are groundwater dependent ecosystems (GDEs). Sufficiently high groundwater levels are required to maintain connection between groundwater levels and the root zones of these ecosystems.

GDEs are defined in the GSP Emergency Regulations as the following based on the California Code of Regulations (CCR) Title 23 § 351 (m):
“Groundwater dependent ecosystem” refers to ecological communities or species that depend on groundwater emerging from aquifers or on groundwater occurring near the ground surface.”

4.3.1 Potential GDE Mapping
In the 2020 GSP, potential GDEs were mapped across the Subbasin. The mapping relied on the Natural Communities Commonly Associated with Groundwater (NCCAG) database, from which additional refinements were made to remove areas that met the following criteria:
• Areas where groundwater levels were deeper than 30 feet below the ground surface (ft bgs). • Areas with access to alternate water supplies that may not be dependent on groundwater (i.e., communities close to managed wetlands, irrigated agriculture, or perennial surface water bodies).

The resulting desktop mapping was then considered by GSA staff and technical workgroup members before inclusion in the GSP. Further detail on this approach to mapping potential GDEs is described in Section 2.2.7 of this GSP Amendment.

Before conducting the analysis to evaluate the potential impacts of the groundwater level SMC on potential GDEs, it was verified that no changes to the NCCAG dataset within the ESJ Subbasin have been made since 2020. The NCCAG database still represents the most comprehensive source of potential GDEs within this Subbasin. Polygons in the NCCAG dataset were removed where the vegetative community’s average maximum rooting depths do not intersect with groundwater. In other words, if the vegetation is not able to access groundwater within its rooting depth, then it is assumed that the ecosystem is not a potential GDE.

This average maximum rooting depth is estimated to be 30 feet below ground surface for the majority of phreatophytes (The Nature Conservancy, 2021). The original mapping completed as part of the 2020 GSP was retained in this GSP Amendment.

The map of potential GDEs included in the 2020 GSP is shown in Figure 5Error! Reference source not found..

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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 5: Mapping of Potential Groundwater Dependent Ecosystems

4.3.2 Impacts to Potential GDEs
While not a comprehensive analysis of potential GDE impacts across the Subbasin, impacts to potential GDEs were assessed in a manner consistent with the analysis completed for well impacts. The delineated polygons in the NCCAG dataset represent mapping of vegetation, wetlands, springs, and seeps across California compiled from 48 publicly available State and Federal agency datasets. The size of the polygon is determined for each ecological grouping using databases that gather information through aerial imagery, remote sensing, and field inspection. The total number of potential GDE polygons identified in the NCCAG dataset within each Impact Zone radii was counted. A count of potential GDEs polygons was assessed, rather than an acreage, due to concerns about how reliable the exact acreages are of the polygon delineations in the NCCAG dataset.

The rooting depth threshold plays a similar role as the 10th percentile threshold in the well impacts analysis by defining at what groundwater level there is an impact or not. It is assumed that if the groundwater level falls below the above thresholds in an Impact Zone, all identified potential GDEs within the Impact Zone ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 would be impacted. Like in the well impact analysis, the impacts are conservatively assumed to be uniform throughout the full Impact Zone. If a potential GDE falls anywhere within an Impact Zone, it is designated as either potentially “impacted” or “not impacted,” depending on where the groundwater level falls in relation to the rooting depth threshold (30 feet below ground surface).

The average simulated water level in 2015 was used to evaluate potential GDE impacts, to maintain consistency with the timing of the filters originally applied in the 2020 GSP. The depth to water dataset used in the 2020 GSP was not available and as a result the simulated water levels used in the 2024 GSP for the impacts analysis are similar but not the same as was used in the 2020 mapping. Using a single year from a model simulation is not ideal, but was selected to be as consistent as possible with the approach taken to develop the mapping. This caveat is discussed in further detail in Section 4.4.1.

It should be noted that the analysis presented herein is based on desktop work only. Field study beyond this analysis will be required to determine the presence, extent, and status of potential GDEs in the Subbasin to inform future assessment.

4.4 Potential GDE Impacts Analysis Results
The results of the impact analysis on potential GDEs are presented in this section, along with a description of its limitations. Impact Zones where potential GDE impacts may occur, as indicated by this desktop analysis, are shown in the Error! Reference source not found.. The count represents the number of identified polygons that may potentially be impacted within each Impact Zone. Under the 48% and 38% undesirable result scenarios described in Section 4.2, there are four Impact Zones that could be at risk of impacting a total of 28 potential GDEs; under the remaining two scenarios, there are three Impact Zones that could be at risk of impacting 14 potential GDEs. The percentage of potential GDEs impacted represents the number of potential GDE polygons at risk of impact compared to the total 602 potential GDE polygons identified across all Impact Zones in the Subbasin. Under the current undesirable result definition (5 RMN wells drop to their minimum threshold), this analysis shows that approximately 2.3% of the potential GDEs within Impact Zones could be impacted. As previously noted, these results are from a desktop only analysis, and do not incorporate any field verification. Therefore, they should be interpreted accordingly as an initial step toward identifying impacts to potential GDEs.

Section 4.4.1 details the limitations and data gaps included in this analysis.

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Technical Memorandum No. 1: Groundwater Levels November 2024 Table 7: Impacts on Potential Groundwater Dependent Ecosystems under Various Undesirable Results Scenarios
Number of Rep MN Wells at MT: 10 8 5 3
% of Rep MN Wells at MT: 48% 38% 24% 14%
Representative Monitoring Network
Impact Zones that May be Impacted
Count of Potential GDEs that May be
Impacted
Manteca 18 8 8 8 8
02N07E29B001 1 1 1 1
04N05E36H003 14 14 0 0
03N06E05N003 5 5 5 5
TOTALS (Within Rep MN Radii) 28 28 14 14
% of Potential GDEs that May be
Impacted, of 602 Potential GDEs
Subbasin-wide

4.7% 4.7% 2.3% 2.3%
While field verification will be needed to best assess the potentially impacted sites in Table 8, a preliminary assessment of Google Earth imagery was completed as a validation check. Figure 7, Figure 8, and Figure 6 show the three Impact Zones where potential GDE impacts are identified under the existing undesirable result scenario: Manteca 18, 02N07E29B001, and 03N06E05N003. In each of these figures, the outlines of the potential GDE polygons are exaggerated in size to better be able to see on this scale, and do not reflect the true size of the potential GDE.

Figure 7 indicates that within the Manteca 18 Impact Zone there are five potential wetland GDE sites and three areas of potential habitat dominated by Valley Oaks that may exist along Lone Tree Slough. Upon further investigation using satellite imagery, the potential wetlands identified may be more likely ponded water on private property. It is difficult to ascertain whether these ponds support an ecosystem fed by shallow groundwater rather than applied water. The ecosystems along the Lone Tree Slough likely do not depend solely on groundwater, given their proximity to water available from the slough. Even if the water in Lone Tree Slough is not perennial, these sites are also adjacent to irrigated agriculture and may be receiving water from these neighboring agricultural areas. These sites may not be potential GDEs, but would require field verification to assess with certainty.

Figure 8 indicates that within the 02N07E29B001 Impact Zone there is one potential wetland GDE. It is difficult to discern in aerial imagery whether this small section of the Calaveras River beneath the rail bridge should be considered a wetland. Most of the Calaveras River is generally considered to be a losing stream (Appendix 3-F) and therefore it may be questionable whether this wetland is fed by groundwater.

Field verification is needed to assess whether this site is a GDE.

Figure 6 indicates that within the 03N06E05N003 Impact Zone there are two areas of potential vegetative GDEs. The area at the far west of the Impact Zone is dominated by Fremont Cottonwood and the area northeast of there is dominated by Hardstem Bulrush. The potential GDE dominated by Fremont Cottonwood is adjacent to irrigated agriculture and an irrigation canal and therefore may not depend on groundwater but rather be receiving water from these neighboring agrictultural areas. The potential GDE dominated by Hardstem Bulrush is a group of polygons adjacent to an Interstate 5 onramp and offramp.

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Technical Memorandum No. 1: Groundwater Levels November 2024 Some of the polygons are also adjacent to irrigated agriculture to the west, while others not directly. It is difficult to determine using aerial imagery whether these ecosystems would have access to an alternative source of water beyond groundwater. Field verification is needed to assess whether these sites are in fact GDEs.

Table 8 contains the locations and supplemental description of each of the NCCAG polygons discussed in the previous paragraphs. The locations shown are the centroid of the NCCAG polygon in decimal degrees.

Figure 6: Map of Impact Zone for GWL Rep MN Manteca 18
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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 7: Map of Impact Zone for GWL Rep MN 02N07E29B001 ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 8: Map of Impact Zone for GWL Rep MN 03N06E05N003 ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 Table 8: Locations of Identified Potential Impacted GDEs Impact Zone
Dominant
Species
(Common
Name)
Dominant
Species
(Scientific
Name)
Wetland
Description
Latitude of
NCCAG Polygon
Centroid
(Decimal
Degrees)
Longitude of
NCCAG Polygon
Centroid
(Decimal
Degrees)
02N07E29B001
Riverine, Lower
Perennial,
Unconsolidated
Bottom,
Permanently
Flooded

37.994 -121.282
03N06E05N003 Fremont
Cottonwood
Populus
fremontii 38.1178 -121.4
03N06E05N003 Fremont
Cottonwood
Populus
fremontii 38.117 -121.401
03N06E05N003 Hardstem
Bulrush
Schoenoplectus
acutus

38.1313 -121.388
Manteca 18 Valley Oak Quercus lobata 37.8555 -121.184
Manteca 18 Valley Oak Quercus lobata 37.8557 -121.186
Manteca 18 Valley Oak Quercus lobata 37.8569 -121.198
Manteca 18
Palustrine,
Emergent,
Persistent,
Seasonally Flooded

37.8208 -121.201
Manteca 18
Palustrine,
Emergent,
Persistent,
Seasonally Flooded

37.8309 -121.167
Manteca 18
Palustrine,
Emergent,
Persistent,
Seasonally Flooded

37.8221 -121.2
Manteca 18
Palustrine,
Emergent,
Persistent,
Seasonally Flooded

37.8227 -121.2
Manteca 18
Palustrine,
Emergent,
Persistent,
Seasonally Flooded

37.8244 -121.145

4.4.1 Limitations and Outstanding Data Gaps for Analysis of Potential GDEs Many of the data gaps identified in the 2020 GSP with regards to evaluating potential GDEs still exist as of the 2024 GSP Amendment. Efforts have been made to address these data gaps, as described in Chapter 7 of this GSP. The five new shallow nested wells installed that comprise the new interconnected surface water ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 representative monitoring network will provide valuable data to assess shallow groundwater conditions along riparian corridors. These wells have not yet been monitored, but data collection will begin with the adoption of the 2024 GSP Amendment.

As of the preparation of this analysis, the following limitations to this analysis and outstanding data gaps should be considered in the interpretation of the presented results. • The impact analysis included in this TM is a desktop only analysis: No field survey has been completed to ground-truth these findings. Field surveys to verify the locations and extent of GDEs should be completed to verify both the mapping used in this analysis and the findings of this analysis.
• The relationship between shallow aquifers and deeper aquifers is still poorly understood: GDEs are, by definition, dependent on water from shallow aquifers and the majority of data available in the Subbasin is from deeper aquifers where production is occurring for drinking or irrigation water. This analysis (conservatively) assumes that the groundwater levels measured in the deeper aquifers at the RMN wells are representative of conditions in all areas of the Impact Zones. This is an imperfect assumption that does not account for how groundwater levels behave along streams because: 1) There is no consideration for the nature of the interaction with the stream or 2) for any localized confining or semi-confining units that may cause perched water tables or other variability in the shallow subsurface.
• The simulated depth to water threshold was model-estimated: 2015 simulated water levels were used in this impact analysis to be consistent with what was done in the 2020 GSP. This poses a limitation to the analysis because it is challenging to model a system with such complexity, at such a local scale. Simulated groundwater levels are not calibrated uniformly across all areas of the Subbasin. Calibration is especially challenging in the shallow subsurface, in which this analysis takes place, due to the lack of shallow groundwater level data available to calibrate to. • The definition of what an ecosystem is in the NCCAG dataset carries a number of assumptions: The size of the polygons in NCCAG is based on how an ecosystem is defined within the dataset, and this incorporates a variety of assumptions into the identification of a potential GDE. For example, two stretches of stream may have similar densities of potential GDEs in the field, but if one reach has more individual species than the other, the two reaches may be classified as more individual GDE polygons despite their similar densities. Therefore, the size of the NCCAG polygons as well as the actual count of GDE polygons should be interpreted cautiously. • The ability to distinguish between percolating surface water and emerging groundwater is difficult:

This is a challenge at both the local scale and the regional scale. Site specific studies are required to make this distinction at the ecosystem scale. At the regional scale, Appendix 3-F makes a preliminary assessment of gaining and losing portions of the Subbasin’s rivers and streams. The analysis showed that on some rivers, gaining and losing portions of the stream can be very variable, such as on the Stanislaus River. However, the analysis contained in that appendix is preliminary and completed without substantial guidance from DWR on how to quantify surface waters that are interconnected. Further detail on the information gaps related to that analysis is detailed in that appendix.
• The lack of overlap between monitoring well locations and locations of potential GDEs: The groundwater level RMN does not substantially overlap with locations potential GDEs may be found.

As stated earlier, the groundwater level RMN was designed for tracking conditions primarily in the ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 principal aquifer where pumping occurs, not for tracking shallow aquifer conditions that potential GDEs would rely on. A new interconnected surface water RMN was developed with six newly constructed wells from which shallow groundwater level measurements will be collected across the Subbasin starting in Fall 2024 (Appendix 3-G). However, these wells are also not co-located to where the identified potential GDEs are (except for the Delta well) because they also were not designed to specifically evaluate GDEs. Therefore, without substantial shallow monitoring data near potential GDE sites, appropriate evaluation of impacts to potential GDEs is difficult.

4.4.2 Plans to Fill Data Gap
To better understand the current conditions of potential GDEs within the Subbasin, additional study is necessary to assess the potential GDEs that currently exist within the Subbasin, as well as the source of their water. For the sites identified as potential GDEs, the following future studies will be completed in order to fill the data gap identified so that GDEs can be more effectively evaluated:
• Evaluate variations between shallow and deep groundwater level measurements at wells in close proximity to rivers and potential GDE areas, including existing nested wells and newly installed shallow wells included in the interconnected surface water RMN. • Conduct field identification for vegetation, wetlands, and wildlife in conjunction with descriptions of local hydrology, including where saturated soils exist, where there is standing surface water, and documentation of evidence of a high water table in the soil. An evaluation of source water for each potential GDE will be evaluated by the biologist.

These two studies will be completed prior to the preparation of the 2030 Periodic Evaluation. If there is strong evidence of GDEs within the Subbasin, the appropriate project and management action(s) will be developed in order to address any site-specific data gaps. This will allow for focused study of potential GDE areas to conserve resources by limiting close study to the highest priority areas. If applicable, a project and management action will be included in a 2030 GSP amendment based on the outcome of these studies.

4.5 Impacts Analysis Conclusion
Impacts to domestic wells are generally more protective of impacts to other wells because they are on average shallower than public supply wells. For this reason, domestic well impacts were incorporated into the calculation of the minimum thresholds in the 2020 GSP, 2022 GSP, and now maintained in the 2024 GSP. Determining the locations of potential GDEs with certainly is difficult to assess with the existing tools.

Using the NCCAG dataset, the preliminary potential GDE impacts analysis included in this TM indicates that the groundwater level SMC are also generally protective of ecosystems dependent on groundwater.

The full impacts analyses included as part of this response to DWR’s recommend corrective actions and the Periodic Evaluation further confirms the original assessment showing that the original 25% threshold undesirable result is protective of domestic wells, public supply wells, and potential groundwater dependent ecosystems (to the extent to which they are known) in the Subbasin.

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Technical Memorandum No. 1: Groundwater Levels November 2024

5. PLAN FOR FUTURE ASSESSMENT OF DEGRADED GROUNDWATER

QUALITY RELATED TO GROUNDWATER LEVELS
Within the Subbasin, there is not significant overlap between wells with available data that are sampled for groundwater levels and quality. An initial analysis of historical observations for nearby wells, however, indicated that there is no obvious relationship between declining groundwater levels and degraded groundwater quality (total dissolved solids [TDS] and chloride). Figure 9 shows the location of three pairs of wells that are within relatively close proximity to each other where groundwater levels and groundwater quality data could be compared. An initial trends analysis is included in Figure 10, Figure 11, and Figure 12 for these three sets of wells. These charts were interpreted cautiously as water quality may vary significantly even within small distances. At each well pair, groundwater levels are from a groundwater level RMW, and groundwater quality data are from a GAMA well. Both TDS and chloride are shown, as these are the two constituents that will be monitored in the new representative network for groundwater quality.

Figure 9: Well Location Map for Initial Trends Analysis ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 10: Initial Trend Analysis at Wells in Close Proximity: CA3910012_046_046 and 02N07E29B001
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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 11: Initial Trend Analysis at Wells in Close Proximity: L10008827999-AMW-24R and 01N07E14J002
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Technical Memorandum No. 1: Groundwater Levels November 2024 Figure 12: Initial Trend Analysis at Wells in Close Proximity: CA3910007_020_020 and 02S08E08A001
For future assessment of the relationship between groundwater levels and groundwater quality, three wells were selected as part of the new representative monitoring network for groundwater quality (detailed in ATTACHMENT 2
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Technical Memorandum No. 1: Groundwater Levels November 2024 TM No. 3), that are also within the representative monitoring network for groundwater levels. These wells are shown in Table 9. This overlap will allow a direct relationship between groundwater levels and groundwater quality to be evaluated as the GSP continues to be implemented. Similar hydro- and chemographs for TDS and chloride will be reported for these three wells in future annual reports. An evaluation of trends will be completed each year to ensure that any interactions between these two sustainability indicators can be identified as early as possible. Additional wells may also be reported on if there is sufficient quality or level data available at another well within the Subbasin.

Table 9: Wells to be Used in Annual Trend Analysis
Representative Monitoring
Network Well
(Groundwater Levels Network and
New Groundwater Quality Network)
Monitoring
Agency
Screen Interval
(if known)
Swenson-3 City of Stockton Clustered
1: 482-502 ft bgs
2: 294-314 ft bgs
3: 194-204 ft bgs
Lodi City Well #2 City of Lodi 110 – 309 ft bgs
Hirschfield (OID-8) Oakdale Irrigation
District
Well Depth = 408 ft
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Technical Memorandum No. 1: Groundwater Levels November 2024

6. CONCLUSIONS
The following summarizes the responses to each part of Recommended Corrective Action 1. 1a) Well (domestic and public supply) and potential GDE impacts analyses were calculated over a range of undesirable result scenarios, ranging from more to less protective than the current definition. The analyses justify the use of 25% in the definition of undesirable results because it represents a compromise between maintaining operational flexibility within the Subbasin while also remaining protective of wells and potential GDEs.
1b) An impacts analysis was completed to evaluate impacts to potential GDEs in a similar manner to the well impacts analyses presented in the 2020 GSP for domestic wells. This desktop analysis showed that while additional study and field verification will be needed, the current undesirable result definition is expected to be protective of impacts to potential GDEs.
1c) The analyses included in the 2020 and 2022 GSPs ensured that domestic well protection was prioritized in the establishment of the groundwater level minimum thresholds. In response to DWR’s RCA #1, a similar approach was taken to also evaluate potential impacts to public supply wells and state small water systems.

These analyses demonstrate that impacts to all three of these well groups are minimal under the current established minimum thresholds and corresponding undesirable result definition. 1d) Going forward, a trends analysis relating groundwater levels and groundwater quality at a minimum of three wells will be included in future annual reports. These three wells are a part of the existing groundwater level representative monitoring network and part of the new groundwater quality representative monitoring network. This will ensure that any relationship between declining groundwater levels and degrading water quality may be detected as early as possible.

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Technical Memorandum No. 1: Groundwater Levels November 2024

7. REFERENCES
California State Water Resources Control Board. (2021). Decision tree for classification of water systems.

Retrieved from
https://waterboards.ca.gov/drinking_water/certlic/drinkingwater/docs/class_dec_tree.pdf The Nature Conservancy. (2021). Plant Rooting Database. Retrieved from https://www.groundwaterresourcehub.org/where-we-work/california/plant-rooting-depthdatabase/ ATTACHMENT 2
ATTACHMENT 2
TECHNICAL MEMORANDUM NO. 2 – Subsidence
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Ashley Couch, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Liz DaBramo and Astrid Guerrero, Woodard & Curran DATE: November 2024
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s July 6, 2023 Approved Determination Letter for the 2022 Revised GSP - Technical Memorandum 2, Response to DWR Recommended Corrective Action No. 2

On July 27, 2022, the Groundwater Sustainability Agencies (GSAs) submitted the Eastern San Joaquin Groundwater Subbasin Revised 2022 Groundwater Sustainability Plan (GSP or Plan) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) to the California Department of Water Resources (DWR) in response to DWR’s incomplete determination letter dated January 28, 2022. In a July 6, 2023 letter, DWR staff concluded that the GSAs had taken sufficient actions to correct deficiencies identified by DWR and approved the 2022 Revised Plan (see Appendix 3-B in the GSP). In Section 6 of the letter, DWR staff also identified recommended corrective actions (RCAs) for the GSAs to address by the Plan’s first periodic evaluation.

This technical memorandum (TM) is in response to RCA # 2 related to subsidence. This TM is organized into the following sections:
1) Overview of Recommended Corrective Action #2
2) Approach to Recommended Corrective Action #2
3) Subsidence Data
4) Representative Monitoring Network (RMN)
5) Sustainability Goal
6) Sustainable Management Criteria (SMC)
ATTACHMENT 2

1. OVERVIEW OF RECOMMENDED CORRECTIVE ACTION #2
The following is the text included in Section 6 of DWR’s July 2023 Determination Letter:

Until a correlation between groundwater levels and land subsidence is established, the GSP should use direct subsidence monitoring data, such as InSAR or CGPS, to define sustainable management criteria (minimum thresholds and undesirable results). In general, the Agencies describe that land subsidence has never been a problem in the Subbasin and imply that land subsidence should not be a problem in the future. If this is accurate, setting land subsidence minimum thresholds using direct monitoring data should not trigger undesirable results and would also be the easiest pathway to developing sustainable management criteria for land subsidence, since a correlation between groundwater levels and land subsidence would no longer need to be established.

Department staff recommend Agencies clearly describe how potential subsidence associated with groundwater level declines below minimum thresholds would not have the potential to cause significant and unreasonable impacts and undesirable results related to subsidence and the use of InSAR data for the land subsidence monitoring network, with supplemental groundwater level data being utilized to evaluate whether detected land subsidence is the result of declining groundwater levels. The use of InSAR data is also recommended for use in establishing a rate and extent in defining significant and unreasonable impacts considered not to cause undesirable results to the Subbasin.

2. APPROACH TO RECOMMENDED CORRECTIVE ACTION #2
The 2020 GSP initially defined Sustainable Management Criteria (SMC) for inelastic land subsidence by using groundwater levels as a proxy. To address DWR’s identified Recommended Corrective Action #2, direct subsidence monitoring data were collected to develop a subsidence-specific representative monitoring network (RMN) and set new SMCs for improved monitoring and management. Direct subsidence monitoring data included Continuous Global Positioning System (CGPS), Interferometric Synthetic Aperture Radar (InSAR), and survey benchmark vertical displacement data. Analyses were conducted to determine whether significant inelastic land subsidence is currently occurring or has historically occurred in the Subbasin. Subsidence rates across the Subbasin were visualized for both CGPS vertical displacement data and InSAR data sets.

Sustainability goals for inelastic land subsidence were established based on impacts to critical infrastructure, the likelihood of undesirable results, and historical subsidence rates. Major roads and water conveyance infrastructure were identified as critical infrastructure, as discussed in Section 5.1. Undesirable results were defined as those causing significant and unreasonable impacts to identified critical infrastructure. New subsidence SMC (undesirable results [UR], minimum thresholds [MTs], measurable objectives [MOs], and interim milestones [IMs]) were developed for cumulative vertical ground surface displacement and 5-year rolling average subsidence rates to identify significant and unreasonable conditions. Additionally, a new representative monitoring network with direct subsidence measurements (as land surface elevation changes) is proposed. Historical subsidence rates and groundwater levels were also examined for potential correlation to confirm that groundwater levels below MTs would not have the potential to cause significant ATTACHMENT 2
and unreasonable impacts and undesirable results related to subsidence. The sections below detail the findings and results of this approach.

3. SUBSIDENCE DATA
Subsidence datasets used to address DWR's RCA #2 include (1) CGPS vertical displacement data from the DWR Sustainable Groundwater Management Act (SGMA) Data Viewer, (2) InSAR subsidence rates from the SGMA Data Viewer, and (3) survey benchmarks from U.S. Geological Survey (USGS), the U.S. Army Corps of Engineers (ACOE), California Department of Transportation (CalTrans), the San Joaquin County Department of Public Works, and local agencies. There are no DWR or USGS extensometers in the Eastern San Joaquin Subbasin. The datasets used are detailed further below.

3.1 CGPS Stations
Vertical displacement data from CGPS stations were downloaded from the DWR SGMA Data Viewer (DWR, 2024). CGPS Stations were selected based on recent data availability, location in the Subbasin, and monitoring status.

Four CGPS stations from UNAVCO and the Scripps Orbit and Permanent Array Center (SOPAC) were available on the SGMA Data Viewer. The two SOPAC CGPS stations considered were P273 and P309. Station P309, in the northeast region of the Subbasin north of the Calaveras River, has a period of record from March 4, 2006, to January 19, 2024. Station P273, in the northwest region of the Subbasin, has data from November 10, 2005, to December 28, 2020. P273 lies in the Delta region of the Subbasin. To set new SMCs, monitoring for inelastic land subsidence in the Subbasin focuses on the non-Delta area as the Delta region contains peaty soils which can subside due to peaty soil oxidation. Peat oxidation occurs when the peaty soils dewater and come into contact with air, causing the soils to break down and compress, and is not a mechanism caused by groundwater overdraft. Consequently, P273 was eliminated from the monitoring network under the SMCs as subsidence in this area likely stems from land reclamation rather than groundwater pumping (SGMA’s focus).

The two UNAVCO CGPS stations considered were CNDR and MTWK. CNDR, in the western region of the Subbasin, has data from April 30, 1999, to February 14, 2006, but is no longer monitored and deemed insufficient for monitoring subsidence. MTWK, in the southern region of the Subbasin south of the city of Manteca, has data from December 12, 2019, to January 19, 2024. This is the closest CGPS station to the Corcoran Clay. Clay-rich zones are prioritized for monitoring since groundwater over-extraction in these areas can lead to dewatering and compression of the clay aquitards and inelastic land subsidence.

Several additional CGPS stations from the University of Nevada Geodetic Laboratory (UNGL) were also considered for subsidence monitoring (UNGL, 2024). These stations provide additional sites for subsidence analysis and the RMN. However, these stations have drawbacks, such as data gaps, and discontinuous monitoring, and are used on an academic/research basis that may result in increased monitoring gaps.

Station CA15 is located north of the city of Stockton and has a continuous period of record between September 2013 and October 2021. Station CMNC is located along the southern edge of the Camanche Reservoir and has observations in 2020 and between February 2022 through January 2024. These locations also provided additional spatial coverage to the UNAVCO and SOPAC CGPS stations.

ATTACHMENT 2
In summary, CGPS Station P309 (SOPAC), MTWK (UNAVCO), CMNC (UNGL), and CA15 (UNGL) were deemed sufficient in combination with published InSAR data to set new subsidence SMCs and the required subsidence-specific RMN. These four CGPS stations will be included in the Subbasin’s RMN.

Figure 1 through Figure 4 show time series graphs of subsidence for the four selected CGPS stations in this analysis. Between 2015 and 2023, all of the CGPS stations showed less than one foot of subsidence was observed throughout the Subbasin. The accuracy of GPS data is estimated to be ± 2 inches (DWR, 2018).

Figure 1 shows a time series graph of subsidence for CGPS Station MTWK. The graph indicates a slight downward trend, reflecting a small increase in subsidence in the Subbasin. From January 2023 to July 2023, subsidence increased slightly more, though overall subsidence remains minimal. The trend line's slope of -0.0295 inches per month (or -0.354 inches per year) confirms that subsidence is occurring in the Subbasin, but at insignificant levels. Additionally, the upward trend of the line at the end of 2023/early 2024 indicates rebound and demonstrates that the subsidence is, to some degree, elastic in nature.

Figure 1: CGPS Station MTWK – Subsidence Time Series
y = -0.0295x + 0.1815
-1.8
-1.3
-0.8
-0.3

0.2 0.7

1.2 2019-112020-052020-072020-092020-112021-012021-032021-052021-072021-092021-112022-012022-032022-052022-072022-092022-112023-012023-032023-052023-072023-092023-112024-01 Vertical Displacement (in)
CGPS Station MTWK
Ave Displacement (in) Linear (Ave Displacement (in))
ATTACHMENT 2
Figure 2 shows a time series graph of subsidence for CGPS Station P309. The graph indicates a very slight downward trend, reflecting a small increase in subsidence in the Subbasin. However, the displacement data varies to a great degree, increasing and decreasing throughout 2006 to current conditions. From June 2015 to June 2016, subsidence increased slightly more with an overall subsidence of approximately 0.7 inches.

This data point represents the largest observed subsidence across the four CGPS stations, but still shows no inelastic subsidence. The trend line's slope of -0.0004 inches per month (-0.005 inches per year) confirms that subsidence occurring in this region is elastic and negligible.

Figure 2: CGPS Station P309 – Subsidence Time Series
Figure 3 shows a time series graph of subsidence for CGPS Station CMNC, located in the northeastern region of the Subbasin along the southern edge of the Camanche Reservoir. Overall, there is a very slight rise in ground elevation that could be due to several factors, such as swelling of clay soils in wet winters.

There is no inelastic subsidence occurring at this CGPS station. As previously mentioned, CPGS Station CMNC is being monitored by UNGL and its data are subject to data gaps and discontinuous monitoring due to its academic nature. While the dataset does not have a long period of record, it supports the observation that subsidence has not historically been an issue in the Subbasin. y = -0.0004x + 0.2946
-1.8
-1.3
-0.8
-0.3

0.2 0.7

1.2 2006-022006-102007-062008-022008-102009-062010-022010-102011-062012-022012-102013-062014-022014-102015-062016-022016-102017-062018-022018-102019-062020-022020-102021-062022-022022-10 Vertical Displacement (in)
CGPS Station P309
Ave Displacement (in) Linear (Ave Displacement (in))
ATTACHMENT 2
Figure 3: CGPS Station CMNC – Subsidence Time Series
Figure 4 shows a time series graph of subsidence for CGPS Station CA1S, located in the western region of the Subbasin, north of the city of Stockton. The graph indicates a downward trend, reflecting a small increase in subsidence in the Subbasin. The subsidence observed for CGPS Station CA1S shows that subsidence was generally increasing in the Subbasin, and this is reflected in the slope of the trendline. The trend line's slope of -0.0286 inches per month (-0.34 inches per year) shows that the rate of subsidence at this region of the Subbasin is relatively greater than that of the other three CGPS stations, but is still relatively minimal as compared to the overall accuracy of the data. The largest observed vertical displacement in this period of record was -0.261 inches, from December 2022 to January 2023, which is a small degree of subsidence. It is important to note that, like CGPS Station CMNC, this dataset is obtained by UNGL and subject to data gaps and discontinuous monitoring.
y = 7E-07x - 0.0275
-1.8
-1.3
-0.8
-0.3

0.2 0.7

1.2 Vertical Displacement (in)
CGPS Station CMNC
Ave Displacement (inches)
ATTACHMENT 2
Figure 4: CGPS Station CA1S – Subsidence Time Series

3.2 InSAR
InSAR data were collected from the SGMA Data Viewer sourced from the California Natural Resources Agency (CNRA). Included in this dataset are point data that represent average vertical displacement values for raster data for total and annual vertical displacement rates in monthly time steps. The longest period of record, at the time of this analysis, was from June 13, 2015, to October 1, 2023.

The subsidence analysis using InSAR data revealed minimal subsidence rates across the Subbasin. The highest observed subsidence rate was in the central portion of the Subbasin, averaging 0.92 inches per year between 2015 and 2023. In contrast, subsidence is not occurring in the eastern region of the Subbasin; instead, the ground elevation has increased due to the swelling of clayey soil in the foothills. This observation is supported by the subsidence analysis for CGPS Station CMNC in the eastern Subbasin which showed positive vertical displacement, indicating a rise in ground elevation. The western region of the Subbasin, adjacent to the Delta, is likely experiencing land subsidence due to peat oxidation rather than groundwater extraction. Figure 5 illustrates that the central portion of the Subbasin in the cone of depression area is more prone to land subsidence and likely related to the lower groundwater levels. Despite this, overall subsidence in the Subbasin remains minimal and is not expected to cause undesirable effects. y = -0.0286x + 0.2332
-1.8
-1.3
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0.2 0.7

1.2 2021-102021-112021-122022-012022-022022-032022-042022-052022-062022-072022-082022-092022-102022-112022-122023-012023-022023-032023-042023-052023-062023-072023-082023-09 Vertical Displacement (in)
CGPS Station CA1S
Ave Displacement (in) Linear (Ave Displacement (in))
ATTACHMENT 2
Figure 5: Subsidence Rates (inches per year) throughout the Subbasin Note: InSAR period of the record displayed in the figure above is June 13, 2015, to October 1, 2023 While CGPS data are more accurate than InSAR vertical displacement measurements, InSAR can estimate subsidence rates over a large land area. Compared to CGPS stations, InSAR has a 16 mm vertical accuracy at a 95% confidence level and an estimated 12 mm (0.47 inches) accuracy near Eastern San Joaquin (Towill, 2020).

3.3 Survey Benchmarks
Survey benchmarks were also considered for this analysis. Survey benchmark data were collected from USGS, ACOE, CalTrans, the San Joaquin County Department of Public Works (DPW), and local agencies.

While there is a high density of benchmarks in the Subbasin, they are not surveyed regularly.

The USGS is installing extensometers and conducting GPS survey campaigns in other Subbasins, but these efforts require a large budget and predominantly focuses on high-subsidence regions; thus, the USGS is ATTACHMENT 2
not expected to construct subsidence monitoring networks in Eastern San Joaquin Subbasin. The ACOE conducts surveys of benchmarks along the San Joaquin River; however, the survey frequency is inconsistent and unknown. Similarly, CalTrans and the San Joaquin County DPW do have survey benchmarks in the Subbasin, but they are also not surveyed regularly and are used primarily on a project-by-project basis.

In March 2024, Stockton East Water District (SEWD) conducted benchmark surveys for subsidence monitoring. The aim was to verify claims by the DWR that approximately seven inches of subsidence had occurred in the area over the past seven years. SEWD surveyed the current elevations of six National Geodetic Survey (NGS) benchmarks with published elevations to compare the historical data with current measurements. These benchmarks, all established in 1962, are located along Comstock Road. The survey results indicated that the average subsidence from the published elevations (1962) to current conditions (March 2024) is approximately 9.3 inches, with a range of subsidence spanning 12.72 inches. The greatest subsidence observed was at NGS Survey Benchmark H-956, which showed a subsidence of 16.56 inches over the 62-year period, or an average subsidence rate of 0.27 inches per year. Due to the temporal differences in subsidence observations, this 62-year period does not provide a precise measurement to directly compare with DWR's InSAR 8-year subsidence data from 2015 to 2023 with an average subsidence rate of 0.92 inches per year.

It is also noteworthy that the six surveyed benchmarks surveyed in 2024 are all located in the central region of the Subbasin, where InSAR data indicated the highest subsidence rate of 0.92 inches per year had occurred. While the subsidence of 16.56 inches at NGS Survey Benchmark H-956 is significant, it must be considered within the context of the 62-year period. The benchmark survey results suggest that subsidence in the Subbasin is not occurring at significant levels and is not expected to cause undesirable effects.

3.4 Subsidence Rates and Groundwater Levels
Historically, the Subbasin has not had significant or undesirable effects caused by inelastic land subsidence.

Examining recent CGPS vertical displacement data, less than one foot of subsidence was observed throughout the Subbasin between 2015 and 2023. While the 2020 GSP originally considered groundwater levels as a proxy for subsidence, a strong correlation was not observed. Undesirable impacts are not expected to occur if groundwater levels drop below the minimum thresholds. Even when groundwater levels have historically dropped below the minimum thresholds, subsidence has not been observed.

Figure 6 shows a time series graph of subsidence (vertical displacement of land surface) and groundwater elevation for CGPS Station MTWK, with Manteca 18 as the respective groundwater level representative monitoring well (RMW). The graph indicates a slight downward trend in land surface elevation, reflecting a small increase in subsidence rates in the Subbasin. From January 2023 to July 2023, land surface elevations increased slightly more when groundwater levels declined, though overall subsidence remains minimal. It is important to note that, while there was a significant drop in groundwater elevations during September 2023, when groundwater levels recovered in the winter of 2024, subsidence reversed. This shows elastic subsidence that can recover with sustainable groundwater levels. Note that the historical groundwater levels in this example did not decline below MT for that RMW.

ATTACHMENT 2
Figure 6: CGPS Station MTWK: Subsidence Time Series
Figure 7 shows a time series graph of subsidence (vertical displacement of land surface) and groundwater elevations for CGPS Station CNDR, with Woodbridge 03N06E05N003 as the respective RMW. The graph indicates a slight downward trend in land surface elevations, reflecting a small increase in subsidence in the Subbasin. The trend line's slope of -0.0105 inches per month confirms that subsidence is occurring at this location in the Subbasin, but at very low levels. There was a significant decrease of 70 feet in groundwater elevation between March 1, 2000 and November 1, 2000 at this groundwater level RMW. Important to note that while there was a sharp decline in groundwater elevation during October 2000, subsidence rates appear to be unaffected. Woodbridge 03N06E05N003 groundwater level RMW was selected for analysis because it is the only RMW that has historically declined below its respective minimum threshold. CNDR CGPS station was selected because it is the only CGPS station with historical observations during the period when the groundwater levels were below the RMW’s minimum threshold.

ATTACHMENT 2
Figure 7: CGPS Station CNDR – Time Series of Subsidence and Groundwater Levels

4. REPRESENTATIVE MONITORING NETWORK
Four CGPS stations were selected for the Subbasin’s Representative Monitoring Network (RMN) for inelastic land subsidence based on data availability, location, and monitoring status. The first station, P309 (SOPAC), is located in the eastern region of the Subbasin, north of the Calaveras River, and provides a comprehensive data record from March 4, 2006, to January 19, 2024. This station was chosen due to its extensive data period and its spatial coverage in the eastern portion of the Subbasin. The second station, MTWK (UNAVCO), is situated in the southern region of the Subbasin, south of the city of Manteca, with data available from December 12, 2019, to January 19, 2024. It is the closest station to the Corcoran clay, an important area to monitor due to the potential for inelastic subsidence near clay-rich areas.

Additionally, two stations from the University of Nevada Geodetic Laboratory (UNGL) were included in the RMN to provide further spatial coverage and address data gaps. The CMNC station, located along the southern edge of the Camanche Reservoir, has data in 2020 and between February 2022 and January 2024.

The CA1S station, north of the city of Stockton, offers a continuous record from October 2021 to September 2023. These stations were selected to enhance the spatial distribution of monitoring locations and continuity of subsidence data in the Subbasin.

Six survey benchmarks from San Joaquin County and NGS were selected to supplement the CGPS data.

Survey benchmarks were also selected to expand the spatial coverage of the subsidence monitoring network in the Subbasin and verify to InSAR data. From San Joaquin County, survey benchmarks M-20 and O-29 were selected. Benchmark M-20 was chosen for the RMN due to its location in the Subbasin, situated in the area with the highest subsidence rate. Benchmark O-29 was selected for its position near a localized, unverified point location of increased subsidence according to InSAR data.

From the NGS, benchmarks Q-833, J-956, G-965, and J-957 were selected. Benchmark Q-833 was chosen due to its proximity to the LODI CGPS Station, its good condition, and elevation observations in 1947 and ATTACHMENT 2
1987. Benchmark J-956 is an important survey benchmark because it was recently surveyed in 2024, is in good condition, and is located in the cone of depression area with higher subsidence rates. Benchmark G965 was selected for the RMN because of its good condition, long period of record dating back to 1962, and its location in the cone of depression area, with the latest survey in 1987. Benchmark J-957 was chosen for its observations in 1962 and 1987, its good condition, and its location in the southeast corner of the Subbasin. InSAR will serve as a supplementary data source for the rest of the Subbasin, and its accuracy will be validated using CGPS and benchmark data.

Table 1 describes monitoring site type, location, and data source for the four CGPS Stations and six survey benchmarks that will make up the Subbasin’s RMN. Figure 8 shows the selected representative monitoring locations across the Subbasin.

Table 1: Subsidence Representative Monitoring Network
Name Type Location (dd) Source
CA1S CGPS Lat: 38.022 N
Long: 121.324 W
UNGL
CMNC CGPS Lat: 38.206 N
Long: 120.999 W
UNGL
MTWK CGPS Lat: 37.778 N
Long: 121.185 W
UNAVCO
P309 CGPS Lat: 38.089 N
Long: 120.951 W
SOPAC
Q-833 Survey Benchmark Lat: 38.130 N
Long: 121.272 W
NGS
J-956 Survey Benchmark Lat: 38.043 N
Long: 121.139 W
NGS
G-965 Survey Benchmark Lat: 38.003 N
Long: 121.139 W
NGS
M-20 Survey Benchmark Lat: 38.014 N
Long: 121.139 W
San Joaquin County
O-29.6 Survey Benchmark Lat: 37.875 N
Long: 121.183 W
San Joaquin County
J-957 Survey Benchmark Lat: 37.856 N
Long: 120.998 W NGS
ATTACHMENT 2
Figure 8: Subsidence Representative Monitoring Network

5. SUSTAINABILITY GOAL

5.1 Critical Infrastructure
Critical infrastructure identified in the Subbasin includes conveyance infrastructure, canals, and pipelines, as well as major roads. The major pipelines selected for this analysis are the East Bay Municipal Utility District’s Mokelumne Aqueduct, stretching from the northeast to the western region of the Subbasin; Stockton East Water District’s major canals and pipelines in the central region; South San Joaquin Irrigation District’s Main District Canal in the southcentral region, and Oakdale Irrigation District’s North Main Canal in the southeastern corner of the Subbasin. The major roadways included are Highway 5 and Highway 99. Figure 9 illustrates all the critical infrastructure, including conveyance systems and major roads, across the Subbasin. Most of the minor canals are concentrated in the southern region of the Subbasin and are displayed for reference purposes only.

ATTACHMENT 2
Figure 9: Critical Infrastructure

5.2 Undesirable Results
Undesirable results from inelastic land subsidence are defined as those causing significant and unreasonable impacts to the critical infrastructure identified in Section 5.1, specifically conveyance infrastructure and major roads. Inelastic land subsidence related to groundwater pumping occurs due to the dewatering of fine-grained geologic materials, such as clay, leading to structural collapse and loss of void spaces. Although there is no significant historical evidence of subsidence in the Subbasin, SGMA requires that the GSP considers the potential consequences of undesirable results.

Per input from the Subbasin GSAs, local infrastructure can typically withstand subsidence ranging between 24 and 36 inches. Based on InSAR data currently, available, 2015-2016 maximum subsidence rates in the Eastern San Joaquin Subbasin ranged from -1.2 inches per year to -2.4 inches per year, and there has been a maximum average subsidence rate of 0.93 inches per year over the last approximately eight years (2015- 2023). Given that approximately 10 years have elapsed since the implementation of SGMA commenced in 2015, and assuming an additional 10 years for achieving significant progress towards the Subbasin’s sustainability goal, it has been assumed that an additional 24 inches of subsidence (-1.2 inches per year ATTACHMENT 2
times 20 years) can occur until 2040 without experiencing undesirable results relating to inelastic land subsidence. Potential effects of inelastic land subsidence in excess of 24 inches include damage to water conveyance facilities and major roads, reduced capacity of surface water delivery systems leading to increased groundwater demand, negative impacts on property values, and economic burdens associated with mitigating the damage.

6. SUSTAINABLE MANAGEMENT CRITERIA
The identified undesirable results described in Section 5.2 and historical subsidence measurements were used as a basis to establish sustainable management criteria for the Subbasin for inelastic land subsidence.

From this basis, new minimum thresholds, measurable objectives, and interim milestones were developed for the Subbasin identifying the total amount (inches) of subsidence and 5-year rolling average rate of subsidence per five-year time period for each SMC.

The subsidence minimum thresholds are established to prevent inelastic subsidence that could affect critical infrastructure. At present, there is no significant inelastic subsidence in the Subbasin affecting any beneficial user, and the minimum threshold is conservatively set to prevent subsidence impacts and allow for adaptive mitigation measures if necessary. The measurable objectives (MOs) and interim milestones are intended to prevent any further subsidence after 2040. Table 2 summarizes the SMCs for the subsidence in the Subbasin to be applied to each representative monitoring location in the Subbasin’s revised RMN for inelastic land subsidence.

Table 2: Subsidence Sustainable Management Criteria
Criteria Time Interval Total Extent
(inches)
5-Year Average Rate
(inches/year)
Minimum Threshold 2020-2040 24 2.4
Measurable Objective After 2040 0 0
Interim Milestones
2020-2025 12 2.4
2025-2030 6 1.2
2030-2035 3 0.6
2035-2040 3 0.6
After 2040 0 0
ATTACHMENT 2
References
California Department of Water Resources (DWR). SGMA Data Viewer, sgma.water.ca.gov/webgis/?appid=SGMADataViewer#waterqual. Accessed 1 Feb. 2024.

California Department of Water Resources: Natural Resources Agency. (2017). GPS Survey of the Sacramento Valley Subsidence Network., 1 Dec. 2018, data.cnra.ca.gov/dataset/gps-survey-of-thesacramento-valley-subsidence-network/resource/f4f0569c-f6dc-46ac-84a2-c71e229c6609. Accessed 1 Feb. 2024.

California Spatial Reference Center, Scripps Orbit and Permanent Array Center (SOPAC). “Data Browser.” sopac-old.ucsd.edu/dataBrowser.shtml. Accessed 1 Feb. 2024.

Towill, Inc. (2020). “InSAR Data Accuracy for California Groundwater Basins: CGPS Data Comparative Analysis.” Siskiyou County - California, Project No.14750-0137, 23 Mar. 2020, www.co.siskiyou.ca.us/sites/default/files/fileattachments/natural_resources/page/28348/appendix_2- d_subsidence.pdf. Accessed 1 Feb. 2024.

UNAVCO. Gage | Data., www.unavco.org/data/data.html. Accessed 1 Feb. 2024.

University of Nevada Geodetic Laboratory (UNGL). Station Pages., geodesy.unr.edu/NGLStationPages/gpsnetmap/GPSNetMap.html. Accessed 1 Feb. 2024.

ATTACHMENT 2
ESJ 2025 GSP Update 1 Woodard & Curran, Inc.

Technical Memorandum No. 3: Groundwater Quality November 2024 TECHNICAL MEMORANDUM NO. 3 – Groundwater Quality
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Ashley Couch, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Liz DaBramo, Emily Honn, and Astrid Guerrero/Woodard & Curran DATE: November 2024
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s July 6, 2023 Approved Determination Letter for the 2022 Revised GSP - Technical Memorandum No. 3, Response to DWR Recommended Corrective Actions Nos. 5, 7, and 8

On July 27, 2022, the Groundwater Sustainability Agencies (GSAs) submitted the Eastern San Joaquin Groundwater Subbasin Revised 2022 Groundwater Sustainability Plan (GSP or Plan) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) to the California Department of Water Resources (DWR) in response to DWR’s incomplete determination letter dated January 28, 2022. In a July 6, 2023 letter, DWR staff concluded that the GSAs had taken sufficient actions to correct deficiencies identified by DWR and approved the 2022 Revised Plan (see Appendix 3-B of the GSP). In Section 6 of the letter, DWR staff also identified recommended corrective actions (RCAs) for the GSAs to address by the Plan’s first periodic evaluation. This technical memorandum (TM) is in response to RCA Nos. 5, 7, and 8 related to groundwater quality and seawater intrusion.

Seawater intrusion and groundwater quality are closely linked, particularly in coastal regions where freshwater and saltwater meet. Excessive groundwater extraction may disrupt the natural hydraulic gradient, allowing seawater to move inland and degrade groundwater. This intrusion increases groundwater salinity, potentially rendering it unsuitable for drinking, irrigation, and industrial use without treatment. Effective management and mitigation strategies are crucial to protect groundwater quality from seawater intrusion.

Regular monitoring of groundwater levels and salinity can help maintain the balance between freshwater and seawater. While the Eastern San Joaquin Subbasin is not on the coast, it abuts the San JoaquinSacramento Delta (Delta) which was a brackish water body before large-scale water management and infrastructure was incorporated.

Given the interconnection of seawater intrusion and groundwater quality, along with the approach described below to DWR’s RCAs, this document includes the response to both the seawater intrusionrelated RCAs (#5 and #8) and groundwater quality RCA (#7) in a single TM. This TM is organized into the following sections:
1) Seawater Intrusion
a. Overview of Recommended Corrective Action #5 and #8
b. 2020 Approach
c. 2025 Approach
d. Supporting Analysis
ATTACHMENT 2
ESJ 2025 GSP Update 2 Woodard & Curran, Inc.

Technical Memorandum No. 3: Groundwater Quality November 2024 e. Response to RCA #5 and #8
2) Groundwater Quality
a. Overview of Recommended Corrective Action #7
b. 2020 Approach
c. 2025 Approach
d. New Groundwater Quality Representative Monitoring Wells (RMW) e. Sustainable Management Criteria (SMC)

1. SEAWATER INTRUSION

1.1 Overview of Recommended Corrective Actions #5 and #8 The following is the text included in Section 6 of DWR’s 2023 Determination Letter:

Corrective Action #5
• Department staff recommend the GSP provide additional explanation for how the 2,000 mg/L chloride isocontour line will prevent significant and unreasonable impacts to beneficial uses and users of groundwater. Additionally, the Plan should provide the current chloride conditions and interim milestones for seawater intrusion.

Corrective Action #8
• The GSP currently states that only groundwater quality wells from the representative monitoring network will be utilized to create the chloride isocontour line that will be used to evaluate seawater intrusion sustainable management criteria. As currently depicted, very few representative monitoring wells are on the western side of the isocontour line. Department staff recommend that development of the chloride isocontour line utilize all groundwater quality wells in the western portion of the Subbasin, as appropriate considering well construction information.

1.2 2020 Approach
The northwest corner of the Eastern San Joaquin (ESJ) Subbasin overlies a portion of the Delta. The Delta originally experienced groundwater fluctuations closely tied to tidal cycles, with a mix of brackish, saline ocean water, and fresh streamflow typical of an inland river delta and estuary. However, after decades of land reclamation and the implementation of managed operations as a result of the State Water Project and Central Valley Project, the Delta is now managed as a freshwater body. Saline water is no longer able to migrate eastward beyond the extensive network of levees and engineering alterations to the original natural channels. As a result, seawater intrusion has not historically been observed within the Subbasin nor is it likely to occur in the future.

The 2020 GSP addressed the potential for seawater intrusion in the Subbasin. As such, a Representative Monitoring Network (RMN) was established, and Sustainable Management Criteria (SMCs) were developed.

A 2,000 mg/L chloride concentration isocontour line, based on the location of monitoring wells, was used as a benchmark for evaluating potential impacts from seawater intrusion. This isocontour line was not based ATTACHMENT 2
ESJ 2025 GSP Update 3 Woodard & Curran, Inc.

Technical Memorandum No. 3: Groundwater Quality November 2024 on existing or historical chloride concentrations; rather, it was delineated to indicate where undesirable results from seawater intrusion could potentially occur in the future. The isocontour line was delineated along the west side of the RMN to ensure that a line of “sentinel” monitoring wells would be able to observe elevated chloride levels before reaching other parts of the Subbasin. A high minimum threshold (MT) of 2,000 mg/L chloride was set to distinguish elevated concentrations derived from seawater intrusion from those derived from naturally occurring high chloride groundwater. Figure 1 shows the delineated chloride isocontour line for the original GSP’s seawater intrusion MT.

Figure 1: 2020 GSP – Seawater Intrusion MT Chloride Isocontour Line Table 1 gives an overview of the 2020 GSP’s SMC for seawater intrusion. Undesirable results were considered to occur when chloride concentrations reached 2,000 mg/L at the established isocontour line, and the source of the elevated concentrations is demonstrated to be a result of groundwater management activities that have induced the intrusion of seawater. This undesirable result was designed to be protective of future changes in Delta tidal patterns as a result of climate change and associated sea level rise or significant changes in Delta management practices. Increased salinity from seawater intrusion could reduce the usable water supply for groundwater users, with domestic wells being most vulnerable due to the high cost of treatment or limited access to alternative supplies. This degradation in water quality could lead to changes in irrigation practices, alterations in crops grown, decreased property values, and other economic ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 impacts. Municipal uses could also be affected, necessitating the installation of treatment systems or the search for alternate water supplies.

Table 1: 2020 GSP – Sustainable Management Criteria for Seawater Intrusion Criteria Narrative Description
Proposed Minimum Threshold (MT) 2,000 mg/L chloride at select wells Proposed Measurable Objective
(MO)
500 mg/L chloride
Proposed Interim Milestones (IMs) 5-yr milestones along linear trend between current conditions and MO
Definition of Unreasonable Result Considered to occur when all representative monitoring wells (RMWs) exceed the MT for seawater intrusion for two consecutive years and where these concentrations are
caused by changes in the hydrologic gradient as it relates to the Delta
A USGS study conducted by O’Leary et. al. (2015) investigated the factors contributing to high chloride concentrations in the Subbasin. The study used major-ion analysis and stable isotope concentrations to determine water types and evaluate groundwater salinity sources in the Subbasin. Figure 2 was presented in the study and illustrates the chloride-to-iodide ratios of water samples from various sources within the Subbasin. It shows that different water sources have distinct chloride-to-iodide ratios and chloride concentrations, allowing for the identification of the origins of high-chloride water. There are three primary sources of high-chloride water in the Subbasin:
• Irrigation return water
• Naturally occurring connate water from deeper deposits • Saline water intrusion from the Delta
Connate water refers to groundwater that has been trapped in the pores of sedimentary rocks since their formation. Often highly saline, connate water typically originates from ancient seawater that was trapped during aquifer formation. Connate water can play a significant role in the hydrogeology and geochemistry of an area, influencing the salinity and chemical composition of aquifers.

The study results mean that high chloride concentrations do not necessarily indicate seawater intrusion.

Connate water can reach concentrations as high as 2,050 mg/L, which exceeds the USEPA Secondary Maximum Contaminant Level (SMCL) of 250 mg/L for chloride. The high chloride concentrations from nonDelta sources resultantly contributed to the high MT established for chloride in the 2020 GSP. Conducting ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 major-ion analysis to determine the source of chloride during semi-annual sampling is economically prohibitive; therefore, no further analyses were conducted to determine the origin of chlorides in the Subbasin.

Figure 2: Chloride-to-Iodide Ratio as a Function of Chloride Concentration (O’Leary, et. al., 2015)

1.3 2025 Approach
To address DWR's Recommended Corrective Action #5, this document aims to demonstrate that seawater intrusion is not an applicable sustainability criterion for the Eastern San Joaquin Subbasin. As outlined in the 2020 approach and the USGS study (O’Leary et. al., 2015), it is challenging to distinguish increased chloride concentrations caused by seawater intrusion from other groundwater quality issues. And given the lack of proximity to the coast and the presence of connate groundwater in the San Joaquin Valley, the seawater intrusion sustainability criterion was reexamined.

The 2025 Periodic Evaluation considered the approach of neighboring subbasins, such as the Tracy and Solano Subbasins which are closer to the saline zone of the Delta, in addressing the seawater intrusion criterion. Both the Tracy and Solano Subbasin GSPs state that seawater intrusion has not and is unlikely to occur in the future, so sustainability criteria were not established in the GSPs. Like the Tracy and Solano Subbasins, the Eastern San Joaquin Subbasin is located in the Delta and is unlikely to experience seawater intrusion in the future with the continued management of the X2 barrier and upstream reservoir releases.

Therefore, this Periodic Evaluation and 2024 Amended GSP addresses DWR’s recommended corrective actions for seawater intrusion by considering the sustainability criterion to not be applicable for the Subbasin for reasons stated below, to eliminate associated SMC for seawater intrusion from the GSP and, instead, incorporate chloride as part of the groundwater quality sustainability criterion, including establishing SMC for chloride under the groundwater quality sustainability criterion.

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Technical Memorandum No. 3: Groundwater Quality November 2024

1.4 Supporting Analysis
The following section provides supporting analysis for this approach by showing:

1. The Delta is managed as a freshwater body in the Subbasin

2. There is minimal pumping in the Eastern San Joaquin Subbasin near the Delta

3. There are relatively low chloride concentrations in the Subbasin

4. Higher salinity water will be addressed through groundwater quality SMCs

5. The Subbasin is committed to monitoring and changing management strategies if conditions worsen

1.4.1 Delta is Managed to Maintain Freshwater Flows
The Subbasin is located adjacent to the Delta region. Prior to the construction of the Shasta Dam in 1943, brackish water had entered the surface waterways throughout the Delta. The Delta ecosystem naturally adapted to a salinity cycle that brought brackish tidal water from the San Francisco Bay. However, the construction of levees for agricultural development, followed by the development and operation of the Central Valley Project and the State Water Project, has changed the pattern of seawater movement into the Delta (Water Education Foundation 2019). Historically, some saltwater may have infiltrated the aquifers, locally affecting groundwater quality. Current management practices aim to maintain freshwater flows in the Delta through a combination of hydraulic and physical barriers and modifications to existing channels (Water Education Foundation 2019). The ”X2” barrier, where the salinity is approximately 2 parts per thousand (ppt), is located well outside of the Subbasin boundary, further downstream in the Delta (Cloern, 2012). (For reference purposes, the salinity of the ocean is about 35 ppt.) Various agencies and regulations, such as the Delta Protection Commission (DPC), Delta Stewardship Council, San Joaquin County & Delta Water Quality Coalition, and State Water Board Resolution No. 2009-011, contribute to managing and maintaining salinity conditions in the Delta region.

1.4.2 Minimal Groundwater Pumping Near the Delta
Figure 3 presents the Subbasin’s 2023 average groundwater pumping in feet across the Subbasin. The majority of pumping is in the northwest portion of Subbasin; areas adjacent to the Delta pump less than half a foot of groundwater per year.

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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 3: 2023 Annual Groundwater Pumping
This figure reflects groundwater pumping from the 2023 Eastern San Joaquin Annual Report. Results may vary with the updated 2024 Eastern San Joaquin Water Resources Model Version 3.0.

1.4.3 Low Chloride Concentrations
Historical and current chloride concentrations were analyzed in the Subbasin. A variety of groundwater quality data were collected and examined. The datasets used for this analysis include (1) the Groundwater Ambient Monitoring and Assessment (GAMA) database, (2) The National Water (NWQMC) database, (3) the region’s Opti Data Management System (DMS), and (4) SGMA Data Viewer (DWR). From these datasets, 4,000 unique wells were utilized with approximately 19,500 chloride observations.

Most wells had chloride concentrations well below the secondary maximum contaminant level (SMCL) of 250 mg/L for chloride. (Secondary MCLs are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. Contaminants with SMCLs are not considered to present a risk to human health and are not enforced.) Chloride concentrations throughout the Subbasin have remained relatively low. Table 2 shows the percentage of chloride measurements after 2015 that exceed thresholds of 250 mg/L, 500 mg/L, and 2,000 mg/L. Notably, ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 the majority of measurements (80%) fell within the 0–250 mg/L range, indicating low chloride levels throughout the Subbasin. Additionally, 14% of chloride observations were in the 250–500 mg/L range.

Overall, 94% of measurements are below the 500 mg/L threshold. This analysis demonstrates that chloride concentrations in the Subbasin are generally low.

Table 2: Chloride Concentrations after 2015
Threshold Concentration Percentage of Measurements after 2015 above Threshold
250 mg/L 14%
500 mg/L 5%
2,000 mg/L 1%
Chloride measurements in Table 2 are based on approximately 19,500 observations from 4,000 unique wells.

Figure 4 shows the average chloride concentration in the Subbasin since January 2015. These results are in line with those of Table 2. As shown in Figure 4, the majority of chloride concentrations in the Subbasin are within the 0 to 250 mg/L range. There are instances of higher concentrations in the 250 to 500 mg/L range, localized within the central and western regions of the Subbasin. Notably, these areas of relatively higher chloride concentrations are not located only in the Delta area and do not form a seawater intrusion front pattern. Overall, concentrations of chloride in the Subbasin are minimal and seawater intrusion is not occurring in the Subbasin or expected to occur in the future.

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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 4: Average Chloride Concentrations Post 2015

1.4.4 Groundwater Quality Monitoring will incorporate Chloride As previously mentioned, high salinity water in the Subbasin is likely not attributed to seawater intrusion, but most likely from other sources of chloride such as irrigation return flows. As demonstrated in the USGS study by O’Leary (O’Leary et. al., 2015), the determination of degraded water quality sources is very complex and infeasible on a regular basis. As such, chloride will be included as a constituent of concern in the groundwater quality sustainability criteria in the 2024 Amended GSP. The RMWs and SMCs for this sustainability criterion are discussed in Section 2.

1.4.5 Commitment to Monitoring and Adaptive Management
The Subbasin is dedicated to monitoring chloride concentrations semi-annually. If salinity conditions were to worsen and deviate from current trends, the Subbasin will adjust management strategies accordingly to ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 manage both chloride and total dissolved solids (TDS) as indicators of degraded groundwater quality.

However, concentrations of chloride in the Subbasin are currently minimal and not expected to change in the future.

1.5 Response to RCA #5 and #8
To address DWR's Recommended Corrective Action #5 and #8, this Periodic Evaluation (and associated GSP amendment) will conclude that seawater intrusion is not an applicable sustainability criterion for the Subbasin and will not set SMCs for seawater intrusion. The approach to respond to RCA #5 and #8 is to remove the associated seawater intrusion SMC (2020 GSP) and add chloride to the groundwater quality SMC. This approach has been confirmed with DWR at a meeting on March 19, 2024.

2. GROUNDWATER QUALITY

2.1 Overview of Recommended Corrective Action #7
The following is the text included in Section 6 of DWR’s 2023 Determination Letter:

Corrective Action #7
• Department staff recommend that existing wells be evaluated to be included as part of the groundwater quality monitoring network to fill data gaps in the eastern portion of the Subbasin, until newly proposed monitoring wells are constructed. Additionally, Department staff recommend the final groundwater quality network identify a monitoring location in the central portion of the Subbasin where the existing groundwater depression was identified.

2.2 2020 Approach
Two monitoring networks were created in the 2020 GSP to track the degraded water quality indicator: the representative monitoring network (RMN) and the broad monitoring network. SMCs were developed for the 10 RMN wells for total dissolved solids. Data collected at these wells have been reported annually through the annual report process. The broad monitoring network included an additional 21 wells intended to add additional monitoring to track the degradation of water quality throughout the Subbasin; however, these wells are not used for compliance with SMCs for groundwater quality. The broad network includes both single-completion wells and nested and/or clustered wells.

Most of the Subbasin’s RMWs for groundwater quality are concentrated mostly on the western portion of the Subbasin where historically water quality has been of lower quality than the eastern side of the Subbasin.

TDS was the only constituent for which SMCs were developed for groundwater quality in the 2020 GSP. The SMCs listed in Table 3 were developed for TDS.

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Technical Memorandum No. 3: Groundwater Quality November 2024 Table 3: 2020 GSP – Sustainable Management Criteria for Groundwater Quality Criteria Narrative Description
Minimum
Threshold
Set at 1,000 mg/L TDS at all RMW locations. The MT is set to protect the beneficial uses of groundwater as a drinking water and agricultural supply. 1,000 mg/L represents the Upper Limit of the SMCL for TDS.

Measurable
Objective
Set at 600 mg/L for TDS at all RMW locations. The MO is also set to ensure the protection of beneficial uses of groundwater as a drinking water and agricultural supply. The SMCL Recommended level of TDS is 500 mg/L. A 100 mg/L buffer was added to the SMCL recommended level to set the MO.

Definition of
Unreasonable
Result
Occurs when more than 25% of the RMWs (3 of 10 sites) exceed the MTs for water quality for two consecutive years, as a result of groundwater management activities.

2.3 2025 Approach
The Subbasin’s approach to addressing DWR’s RCA #7 involves streamlining and combining representative and broad network wells into a unified set of RMWs. This new set of wells will cover the spatial extent of the Subbasin and follow the recommendations outlined in the DWR Monitoring Network Best Management Practices (BMPs) (DWR 2016).

As part of this approach, the Subbasin analyzed available wells with recent TDS data from the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The locations, observations, and concentrations of the new set of monitoring wells were examined, as shown in Figure 5 through Figure 7. The chloride data collected to respond to RCA #5 and #8, described in Section 1, were also analyzed. The well characteristics and groundwater quality observations were used to inform the selection of a new RMN with updated SMCs.

Figure 5 illustrates the count of TDS groundwater quality observations for each well between January 2015 and January 2024. The majority of wells have 10 or fewer observations, indicating that most wells were not sampled on an annual basis. Several wells closer to the city of Stockton have up to 50 groundwater quality observations. The wells with the highest sample count appear to be located near groundwater cleanup sites.

Ideally, wells in the RMN would have been sampled regularly; however, wells that were located in the specific areas requested in RCA #7 were not sampled frequently (greater than 10 times) in recent years.

Figure 6 displays wells with TDS observations in recent years (2015 through early 2024) by well depth. The threshold between shallow and deep wells was set at 200 feet for consistency with the 2020 GSP. There were several wells without perforation or depth information. Between shallow, deep, and unknown well depths, there is a similar distribution of high- and low-quality groundwater. In other words, TDS was not observed in just the shallow or deep aquifer. The expanded groundwater quality RMN includes wells perforated at varying well depths to capture vertical differences in groundwater quality, as described in Section 2.4.

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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 7 illustrates the maximum TDS concentrations since January 2015. The majority of wells have TDS concentrations below the measurable objective of 600 mg/L. However, some wells have recent TDS concentrations above minimum threshold of 1,000 mg/L. These wells are primarily located near the city of Stockton. Public water purveyors closely monitor groundwater quality and source and treat their water accordingly. The expanded RMN is intended to monitor groundwater quality concentrations and trends to avoid undesirable impacts and worsening of groundwater conditions as a result of groundwater pumping and management.

Figure 5: Monitoring Frequency for Wells Measuring Total Dissolved Solids ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 6: Wells with Recent TDS Observations by Well Depth ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 7: Maximum Concentrations for Wells Measuring Total Dissolved Solids

2.4 New Groundwater Quality RMWs
In response to DWR’s 2023 Determination Letter, the RMN for water quality was improved in the 2024 Amended GSP. The original 10 wells from the 2020 RMN were retained, and 11 wells were added. New wells were included to improve coverage in the eastern side of the Subbasin and within the groundwater depression in the north-central portion. Wells were selected in accordance with DWR’s Monitoring Networks and Identification of Data Gaps Best Management Practice (DWR 2016). Figure 9 shows the final updated 2024 Amended RMN for groundwater quality. Information on these wells is detailed in Table 4. For each well, the table includes appropriate well IDs, a description of the wells, monitoring agency, location, and the screen internal and well depth.

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Technical Memorandum No. 3: Groundwater Quality November 2024 The following summarizes the 11 new wells that were added to the representative network in further detail.

Figure 9 displays the groundwater quality RMN by source. • New Stockton Wells: Stockton 26 in the original representative monitoring network has been decommissioned since the 2020 GSP. Therefore, Stockton 26 was removed, and as part of the 2024 Amended RMN, Stockton 27 and 31 have been added to the representative network. These two new wells will be monitored in addition to the remaining two Stockton wells in the existing network, for a total of four RMWs in the city of Stockon.
• R epresentative Network for Groundwater Levels: Swenson-3, Lodi City Well #2, and OID-8 are groundwater level RMWs that have been added to the network for groundwater quality. These wells expand coverage within data gap areas. Additionally, these wells also serve to support the Subbasin’s response to Recommended Corrective Action #1, where the Subbasin is committing to tracking trends in groundwater quality with trends in groundwater levels at these three wells. While there is not evidence of a strong connection between declining water levels and degraded water quality, these wells will be used to track trends in both annually going forward. • Ex isting Broad Monitoring Network Well: One well from the 2020 GSP’s broad monitoring network, CCWD 010/011/012, was included in the updated network in the 2024 Amended RMN. This well provides beneficial spatial coverage in the northeast part of the Subbasin as well as valuable coverage at various depths.
• A dditional Wells: Five wells, new to the 2024 Amended GSP, were added to the RMN. These wells include Well No. 05 monitored by Lockeford CSD, Well No. 07 monitored by Linden County WD, Well #2 at Shady Rest Trailer County, and Well No. 11 and 16 monitored by the city of Ripon. Each of these wells fill remaining data gaps on the eastern side and southern portion of the Subbasin.

Several of these wells are already being monitored for California Water Watch through the State Water Resources Control Board every three years. Permission was obtained by each of these monitoring entities and a commitment to monitor for SGMA compliance has been made going forward.

The updated groundwater quality RMN has a diverse vertical extent and spans both shallow and deep aquifers. Several wells have multiple completions. This allows for a three-dimensional mapping of degraded water quality, as recommended by DWR’s Monitoring Network BMPs. Figure 9 shows the source of each well in the groundwater quality RMN, and Figure 10 shows the well depth of each groundwater quality RMW. Table 4 lists the well ID, monitoring agency, location, and perforation data for each groundwater quality RMW.

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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 8: Updated Groundwater Quality Representative Monitoring Network ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 9: Updated Groundwater Quality RMN by Source
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Technical Memorandum No. 3: Groundwater Quality November 2024 Figure 10: Updated Groundwater Quality RMN by Well Depth ATTACHMENT 2
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Technical Memorandum No. 3: Groundwater Quality November 2024 Table 4: 2024 Amended Representative Monitoring Network for Groundwater Quality – Well List GSP Well ID CASGEM ID GM Well ID Monitoring Agency LATITUDE LONGITUDE Source Screen Group Screen Top
Screen
Bottom
Well Depth
Well 1 381154N1213818W001 CA3901248_001_001 San Joaquin County (Flag City) 38.115366 -121.381755 2020 RMW Shallow (less than 200') 110 170 - Well 2 381131N1213920W001 CA3901248_002_002 San Joaquin County (Flag City) 38.113064 -121.391997 2020 RMW Shallow (less than 200') 110 170 - Well 3 381130N1213887W001 San Joaquin County (Flag City) 38.11299 -121.388682 2020 RMW Unknown - - - 119-075-01 01N/07E-18D01M CA3910001_063_063 Cal Water 37.980357 -121.263022 2020 RMW Deep (greater than 200') 200 560 - Well 15 378089N1212325W001 CA3910005_015_015 City of Manteca 37.808954 -121.232674 2020 RMW Both 140 240 - Well 16 377904N1212476W001 CA3910005_016_016 City of Manteca 37.790339 -121.247724 2020 RMW Both 137 274 - Well 17 378059N1211878W001 CA3910005_028_028 City of Manteca 37.805695 -121.18896 2020 RMW Both 110 230 - Stockton 27 City of Stockton 37.994542 -121.282878 2023 AR Shallow (less than 200') 0 200 - Stockton SSS8 379146N1212401W001 CA3910012_089_089 City of Stockton 37.91465 -121.237343 2020 RMW Both 158 256 - Stockton 31 CA3910012_094_094 City of Stockton 38.045846 -121.263778 2023 AR Multiple Wells1 157 362 380 Stockton 10R 380292N1212843W001 CA3910012_100_100 City of Stockton 38.028706 -121.285004 2020 RMW Multiple Wells2 164 488 498 Well No. 05 CA3910008_005_005 Lockeford CSD 38.155478 -121.150908 New CA7 Deep (greater than 200') 250 310 - Well No. 07 CA3910019_007_007 Linden County WD 38.025715 -121.088695 New CA7 Deep (greater than 200') 480 600 - Well #2 CA3900755_002_002 Shady Rest Trailer Court 37.994757 -121.171349 New CA7 Deep (greater than 200') 200 210 - WELL NO. 11 CA3910007_012_012 City of Ripon 37.729054 -121.141496 New CA7 Shallow (less than 200') 125 155 163 WELL NO. 16 CA3910007_026_026 City of Ripon 37.7510854 -121.1264178 New CA7 Deep (greater than 200') 232 356 366 Swenson-3 380067N1213458W003 38.0067 -121.3458 GWL RMN Multiple Wells3 194 502 Lodi City Well #2 CA3910004_003_003 City of Lodi 38.1376 -121.274 GWL RMN Both 110 309 - Hirschfeld (OID-8) Oakdale ID 37.8352 -120.957 GWL RMN Deep (greater than 200') - - 408 CCWD 010, 011, 012 Calaveras County WD 38.16278308 -120.92918 Broad Monitoring Network Multiple Wells4 115 390 1 Screened: 157-172, 183-207, 308-328, 337-362 feet deep 2 Screened: 164-172, 180-194, 208-266, 294-306, 358-412, 452-466, 474-488 feet deep 3 Screened 1: 482-502, 2: 294-314; 3:194-204 feet deep
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Technical Memorandum No. 3: Groundwater Quality November 2024

2.5 Sustainable Management Criteria
SMCs were established for each RMW for TDS and Chloride.

The TDS SMCs remained unchanged from the 2020 GSP and were applied to the new RMWs. The ESJ Groundwater Authority Board selected an MT of 1,000 mg/L based on stakeholder concerns for drinking water and agricultural beneficial uses. The MO was set to 600 mg/L based on the TDS recommended SMCL for drinking water of 500 mg/L and adding a 100 mg/L buffer. The 600 mg/L TDS measurable objective is close to the recommended SMCL of 500 mg/L and significantly below the upper limit SMCL of 1,000 mg/L and is considered adequate for drinking water and agricultural uses. More information about the establishment of TDS SMC is described in Section 3.3.3 of the 2020 GSP.

The chloride SMCs aimed to avoid worsening groundwater quality from 2015 conditions. The MT for chloride was set at the maximum of the chloride SMCL (250 mg/L) or 2015 conditions, whichever is greater.

All RMWs had chloride concentrations below the SMCL; therefore, the MT for all groundwater-quality RMWs is 250 mg/L. The chloride MO is equal to current conditions, established at the maximum of recent historical conditions between 2015 and 2023.

For both TDS and chloride, the interim milestones are the MO (if current concentrations are currently at the MO), or along an allowable linear increase in concentrations in groundwater until the MO is reached.

Concentrations at the MO would subsequently be maintained after 2040. Increases in TDS and chloride in concentrations are considered to be allowable up to the MO because:
• For chloride, the largest difference between average current conditions and the MO for chloride is 24 mg/L with an average difference of 3 mg/L. Based on limited historical data, the average variation in chloride concentrations in the Subbasin is approximately 8 mg/L. For TDS, the largest difference between average current conditions and the MO for TDS is 358 mg/L with an average difference of 51 mg/L. Based on limited historical data, the average variation in TDS concentrations in the Subbasin is approximately 82 mg/L. Therefore, the average variation in concentrations is on par with the average existing differences in concentration between current conditions and the respective constituent MOs.
• Proximity to the Delta is one possible reason for increased TDS and/or chloride concentrations in groundwater. Delta salinity concentrations are managed by the State, and the portion of the Delta in the Eastern San Joaquin Subbasin is managed as a freshwater body. The GSAs can manage groundwater pumping in the Subbasin, which is relatively low in the Delta area, to reduce the potential of chloride intrusion. However, the salinity of the Delta from changing reservoir operations upstream and outside of the Subbasin is outside of the management scope of the GSAs. • Irrigation return flows are another possible reason for increased concentrations of TDS and/or chloride in groundwater. The Subbasin depends heavily on agriculture for its local economies, and limiting agricultural uses would impact the basin. Agricultural sources of salinity are managed through existing management and regulatory programs within the Subbasin, such as the Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) and the Irrigated Lands Regulatory Program (ILRP).

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Technical Memorandum No. 3: Groundwater Quality November 2024 Table 5 summarizes the approach to establishing the groundwater quality SMCs for TDS and chloride.

Table 6 details the recent groundwater quality observations and MOs/MTs for each RMN. Each RMW will be monitored semi-annually, once in spring and once in fall, and reported in the Annual Reports.

Table 5: Summary of Groundwater Quality SMC Approach
Criteria Chloride TDS
Measurable Objective Maximum recent historical
conditions (2015-2023)
600 mg/L
Interim Milestones Current concentration or
linear increase to MO
Current concentration or
linear increase to MO
Minimum Threshold 250 mg/L (SMCL), or chloride
concentrations as measured
in 2015 (whichever is greater)
1,000 mg/L (SMCL), or TDS
concentrations as measured
in 2015 (whichever is
greater)
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Technical Memorandum No. 3: Groundwater Quality November 2024 Table 6: Groundwater Quality RMN and Recent Groundwater Quality Observations and SMCs GSP Well ID Average
Chloride
(2015-
Present)
Max
Chloride
(2015-
Present)
Average
TDS (2015-
Present)
Max TDS
(2015-
Present)
Chloride
MO
Chloride MT TDS
MO
TDS MT
Well 1 34.6 36 445 470 36 250 600 1,000
Well 2 73 73 568 590 73 250 600 1,000
Well 3 34.6 36 520 570 36 250 600 1,000
119-075-01 26.6 30 360 380 30 250 600 1,000
Well 15 15.8 17 310 310 17 250 600 1,000
Well 16 12.83 16 250 260 16 250 600 1,000
Well 17 15.2 17 305 320 17 250 600 1,000
Stockton 27 10.34 26 65 65.3 26 250 600 1,000
Stockton SSS8 38.5 41 330 330 41 250 600 1,000
Stockton 31 27.4 51 301 480 51 250 600 1,000
Stockton 10R 18 20 390 390 20 250 600 1,000
Well No. 05 14.7 17 227 240 17 250 600 1,000
Well No. 07 3.5 3.8 173 180 3.8 250 600 1,000
Well #2 16.3 33 323 520 33 250 600 1,000
WELL NO. 111 75.5 83 610 610 83 250 600 1,000
WELL NO. 161 75.5 83 580 580 83 250 600 1,000
Swenson-32 100 100 250 600 1,000
Lodi City Well #2 6.2 6.2 190 190 6.2 250 600 1,000
Hirschfeld (OID-8) 12 12 200 200 12 250 600 1,000
CCWD 010, 011, 0123 250 600 1,000
Note: all concentrations in mg/L
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Technical Memorandum No. 3: Groundwater Quality November 2024 1No recent chloride observations. Reported chloride concentrations from nearby WELL NO. 3. (CA3910007_003_003) from January 2015, January 2018, and January 2021.
2Swenson-3 is currently not accessible, but since it is originally a GWL RMN, it is expected to be accessible going forward. If not, then another well will be selected to replace it. There are no recent groundwater quality observations and the reported data is from nearby well ID CA3910012_030_030 in October 1991.
3No recent or nearby groundwater quality observations.

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Technical Memorandum No. 3: Groundwater Quality November 2024

3. REFERENCES
California Department of Water Resources. (2014). SGMA Data Viewer. https://sgma.water.ca.gov/webgis/?appid=SGMADataViewer#boundaries.

California Department of Water Resources. (2016). Best Management Practices for the Sustainable Management of Groundwater; Monitoring Networks and Identification of Data Gaps. water.ca.gov/- /media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Sustainable-GroundwaterManagement/Best-Management-Practices-and-Guidance-Documents/Files/BMP-2-Monitoring-Networksand-Identification-of-Data-Gaps_ay_19.pdf.

Cloern, James & Jassby, Alan. (2012). Drivers of change in estuarine-coastal ecosystems: Discoveries from four decades of study in San Francisco Bay. Reviews of Geophysics. 50. 1-33. 10.1029/2012RG000397.

O'Leary, David, John Izbicki, and Loren Metzger. (2015). Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California, USA. Hydrogeology Journal. 23. 10.1007/s10040-015- 1277-7.

State Water Resources Control Board (SWRCB) (2024). Groundwater Ambient Monitoring and Assessment (GAMA) Groundwater Information System.
https://gamagroundwater.waterboards.ca.gov/gama/gamamap/public/.

U.S. Environmental Protection Agency (2024). National Water Quality Monitoring Council. https://www.epa.gov/awma/national-water-quality-monitoring-council.

Water Education Foundation. 2019. 2019 Annual Report.
https://www.watereducation.org/sites/main/files/file-attachments/2019annualreport.pdf ATTACHMENT 2
ATTACHMENT 2
ESJ 2024 GSP Update 1 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 TECHNICAL MEMORANDUM NO. 4 – Water Budgets and
Groundwater Storage
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Ashley Couch, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Emily Honn, Woodard & Curran
DATE: November 2024
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s July 6, 2023 Approved Determination Letter for the 2022 Revised GSP - Technical Memorandum No. 4, Response to DWR Recommended Corrective Actions Nos. 3 and 4
On July 27, 2022, the Groundwater Sustainability Agencies (GSAs) submitted the Eastern San Joaquin Groundwater Subbasin Revised 2022 Groundwater Sustainability Plan (GSP or Plan) for the San Joaquin Valley – Eastern San Joaquin Subbasin (Subbasin) to the California Department of Water Resources (DWR) in response to DWR’s incomplete determination letter dated January 28, 2022. In a July 6, 2023 letter, DWR staff concluded that the GSAs had taken sufficient actions to correct deficiencies identified by DWR and approved the 2022 Revised Plan (see Appendix 3-B in the GSP). In Section 6 of the letter, DWR staff also identified recommended corrective actions (RCAs) for the GSAs to address by the Plan’s first periodic evaluation.

This technical memorandum (TM) is in response to RCAs #3 and #4 related to clarifying water budget assumptions and revising the sustainable management criteria (SMC) for groundwater storage. As part of the GSP implementation and in response to RCAs #3 and #4, the Eastern San Joaquin Water Resources Model (ESJWRM) was updated in 2024 to reflect the latest data and groundwater conditions, as documented in the 2024 Model Documentation Update (Woodard & Curran, 2024). Groundwater storage in the Subbasin is estimated using ESJWRM Version 3.0 and therefore, total Subbasin storage was revised with this significant model update. For this reason, the Subbasin’s response to RCAs #3 and #4 are combined into this single TM.

This TM is organized into the following sections:
1) Water Budget Updates
a. Overview of Recommended Corrective Action #3
b. Development of ESJWRM Version 3.0
c. Updated ESJWRM Version 3.0 Water Budget Tables
2) Groundwater Storage
a. Overview of Recommended Corrective Action #4
ATTACHMENT 2
ESJ 2024 GSP Update 2 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 b. 2020 Approach
c. 2024 Updated Approach

1. WATER BUDGET UPDATES

1.1 Overview of Recommended Corrective Action #3
The following is the text included in Section 6 of DWR’s 2023 Determination Letter:

Department staff recommend that in the first periodic evaluation of the GSP, only water budgets developed from the most recent or best available data be included. As currently presented, it is unclear whether the sustainable yield estimate and estimated groundwater offset required to achieve sustainability are based on the updated modeling results (based on ESJWRM Version 2.0) or are from the modeling scenarios presented in the original GSP submitted in 2020 (based on ESJWRM Version 1.0).

1.2 Development of ESJWRM Version 3.0
In response to RCA #3 and in conjunction with the development of the first periodic evaluation of the ESJ GSP, ESJWRM underwent a significant update in 2024. ESJWRM Version 3.0 now represents the latest working version of the model. The historical conditions, current conditions, projected conditions baseline, and projected conditions scenarios have been re-developed using ESJWRM Version 3.0. The results of these scenarios are included in this TM as well as in the first GSP Periodic Evaluation and 2024 GSP Amendment.

ESJWRM Version 3.0 includes the following major modeling updates:
• Updated historical model
• Calibrated historical model (Historical ESJWRM Version 3.0) • Updated model scenarios
o Current Conditions (methodology change in estimating current conditions from 2020 ESJ GSP)
o Projected Conditions Baseline or PCBL Version 3.0 (no major changes from Version 2.0) o Projected Conditions Baseline with Climate Change or PCBL-CC Version 3.0 (no major changes from Version 2.0)
o Projected Conditions Baseline with Demand Reduction or PCBL-DR Version 3.0 and Projected Conditions Baseline with Climate Change and Demand Reduction or PCBL-CCDR Version 3.0 (no major changes in approach from Version 2.0) o Projected Conditions Baseline with Projects & Management Actions or PCBL-PMA Version

3.0 and Projected Conditions Baseline with Climate Change and Projects & Management Actions or PCBL-CC-PMA Version 3.0 (no major changes in approach from Version 2.0) ATTACHMENT 2
ESJ 2024 GSP Update 3 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 • Updated water budgets based on ESJWRM Version 3.0
Major changes to the ESJWRM model are described in the 2024 Model Documentation Update (Woodard & Curran, 2024). ESJWRM Version 3.0 will be used going forward as the latest version of the model. It was used to address RCA #4 and #6 in response to DWR’s 2023 Determination Letter. A review of how it was used to address RCA #4 is included in Section 2 of this TM; how it was used to address RCA #6 is described in detail in Technical Memorandum No. 5 (ISW TM).

1.2.1 Summary of Significant Historical Model Updates in ESJWRM Version 3.0 A more comprehensive summary is included in the 2024 Model Documentation TM (Woodard & Curran, 2024), but a summary of the major model changes that were made is included below in Table 1.

Table 1: Historical Model Data and Feature Updates
Model Element 2024 Update
Layering Refined based on AEM and added shallow alluvium layer Streams Removed Bear Creek from simulated streams
Land Use Incorporated most recent DWR Statewide Crop Mapping (5 years: 2018, 2019, 2020, 2021, 2022) and removed previous data used for WY 2007- 2015
Urban Water Demand Updated rural residential population estimate using Census Tract data Surface Water Supply Added estimate of Farmington seepage and revised carriage/canal losses for SEWD. Made slight adjustments to diversions for NSJWCD, OID, and SSJID.

SW and GW Delivery Groups Small updates based on local information received and to limit area overlaps

1.2.2 Summary of Current Conditions Scenario Updates using ESJWRM Version 3.0 The methodology used to develop the estimate of current conditions in the Subbasin was updated in ESJWRM Version 3.0. The 2020 GSP used a separate baseline model to estimate current conditions in the Subbasin over 50 years of historical hydrology. The methodology was updated in 2024 to remove reliance on a separate model run and instead focus on the recent years in the Historical ESJWRM Version 3.0.

Current conditions in Version 3.0 are represented as an average of the last five water years (2019-2023) in Historical ESJWRM Version 3.0. This includes three (3) dry years and two (2) wet years. Current conditions are continuously changing by nature of what the scenario represents and are summarized in the Subbasin Annual Reports. Under this iteration of current conditions, an increased change in storage can be observed, which is consistent with recent trends in groundwater levels. There is an increased agricultural demand relative to the longer historical period but decreased urban demand due to conservation policies despite urban expansion.

ATTACHMENT 2
ESJ 2024 GSP Update 4 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024

1.2.3 Summary of Projected Conditions Scenario Updates using ESJWRM Version 3.0 The Projected Conditions Baseline (PCBL) Version 3.0 and Projected Conditions Baseline with Climate Change (PCBL-CC) Version 3.0 were revised based on updates made to the Historical ESJWRM Version 3.0 model. The simulation period was extended to 55 years; otherwise, assumptions of projected conditions remained the same as in PCBL Version 2.0.

Though not required by the SGMA regulations, updates to the Projected Conditions Baseline with Demand Reduction (PCBL-DR) Version 3.0 and Projected Conditions Baseline with Projects & Management Actions (PCBL-PMA) Version 3.0 scenarios, both with and without climate change, were also updated using PCBL Version 3.0 and PCBL-CC Version 3.0. These scenarios are important tools used within the ESJ Subbasin to better understand the relative benefits of supply and demand side solutions on the path toward subbasin sustainability. The approach used to develop these scenarios remained the same as is included in the 2022 Revised GSP, however, a few assumptions were updated based on input from the Eastern San Joaquin Groundwater Authority (ESJGWA) Project Management Committee (PMC). The following two sections detail some of the updates to these scenarios.

PCBL with Demand Reduction and PCBL with Climate Change and Demand Reduction The demand reduction scenario models the impact of decreasing urban and agricultural demand across the Subbasin in order to understand what groundwater pumping reduction may be necessary to achieve a longterm groundwater storage deficit of approximately zero. An additional demand reduction scenario that includes the possible impacts of climate change was also rerun as part of the 2024 update.

The same approach used in 2022 was applied to the 2024 update. However, with the updated version of the model, a few modifications to the assumptions were made in order to achieve an annual average change in storage of zero. Both the PCBL scenario with climate change (PCBL-CC-DR Version 3.0) and without climate change (PCBL-DR Version 3.0) were developed.
• Urban Demand: Urban per capita water use was reduced by 15% under both PCBL-DR Version

3.0 and PCBL-CC-DR Version 3.0. This reduction is not indicative of how potential future urban demand cutbacks may be implemented.
• Agricultural Demand: Agricultural groundwater pumping was reduced in areas further than one (1) mile from streams by reducing agricultural acreage. Larger users of agricultural groundwater in ESJWRM were reduced at higher percents compared to smaller users. This reduction is not indicative of how potential future agricultural demand cutbacks may be implemented.

Table 2 shows how these percent reductions varied by type of user for each scenario. Further detail can be found in the 2024 Model Documentation TM (Woodard & Curran, 2024).

ATTACHMENT 2
ESJ 2024 GSP Update 5 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Table 2: Percent Demand Reduction Applied by Type of User Percent Reduction PCBL-DR
Version 3.0

PCBL-CC-DR
Version 3.0
Ag GW Pumping <2 AF/acre 0% 0%
Ag GW Pumping 2-3 AF/acre 15% 25%
Ag GW Pumping >=3 AF/acre 28% 38%
Urban Demand 15% 15%
PCBL with Projects & Management Actions and PCBL with Climate Change and Projects & Management Actions
The 2022 Revised GSP categorized projects and management actions into two categories: Category A and Category B projects. Category A projects are likely to advance in the next five years and have existing water rights or agreements in place. Category B projects are not anticipated to advance in the next five years but could be leveraged in the future. Category B projects may be elevated the Category A list should the appropriate project specifications be met.

A formal call for projects was initiated on April 26, 2024, so that GSAs could either provide updates on existing Category A and B projects or add new projects. Project status, timeline, benefits, and description were updated. Two new projects were added to the Category A list: NSJWCD Private Pumping Partnerships and OID In-Lieu and Direct Recharge. Table 3 show the updated Category A list of projects. Table 4Table 3 show the updated Category B list of projects. Four new additional Category B projects were approved by the ESJGWA Board at their September 11, 2024 meeting and are not included in Table 4. More information on these projects is included in Appendix 6-A.

There are a total of 13 Category A projects. Seven are in-lieu recharge projects, three are direct recharge projects, and three are a combination of in-lieu recharge and direct recharge. Overall, the total additional surface water provided by Category A projects (either by in lieu or direct recharge) varies by water year type and ranges from 36,000 to 96,000 acre-feet per year (AFY) and is a mixture of deliveries to agricultural customers (including assumptions on evaporation and delivery losses), deliveries to urban customers, and direct recharge projects. A summary of the total additional water supply (excluding assumed losses) anticipated from Category A projects is included in Table 3.

Category A projects are simulated in ESJWRM to show the impact of these likely projects on the Subbasin under both the with climate change (PCBL-PMA-CC Version 3.0) and without climate change (PCBL-PMA Version 3.0) scenarios. Both scenarios reduce the reliance on groundwater by increasing in-lieu recharge in the Subbasin and directly reduce the change in groundwater storage via increased groundwater recharge projects. Though both scenarios do still indicate some additional projects or demand reductions may be needed, the Category A projects that are planned and being actively undertaken by the GSAs will improve sustainability in the Subbasin. Further detail, including results, can be found in the 2024 Model Documentation TM (Woodard & Curran, 2024).

ATTACHMENT 2
ESJ 2024 GSP Update 6 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Table 3: List of Category A Projects (2024)
Activity Project Type Project
Proponent
Schedule
(initiation
and
completion)
Baseline
Water
Year Type
Annual
Volume (AFY)
in PCBL-PMA
Version 3.0
and PCBL-CCPMA Version

3.0 SEWD Lake Grupe Inlieu RechargeIn-Lieu
Recharge
SEWD 2020-2023 Drought 2,000
Dry 4,900
Normal 4,900
Wet 4,900
SEWD Surface Water
Implementation
Expansion
In-Lieu
Recharge
SEWD 2019-2029 Drought 4,000
Dry 8,000
Normal 19,000
Wet 19,000
SEWD West
Groundwater
Recharge Basin
Direct Recharge SEWD 2032 Drought 1,500
Dry 4,000
Normal 16,000
Wet 16,000
CSJWCD Capital
Improvement
Program
In-Lieu
Recharge
CSJWCD 2020-2027,
on-going
with 7-year
completion
cycles
Drought -
Dry 12,000
Normal 24,000
Wet 24,000
Long-term Water
Transfer to SEWD
and CSJWCD
Transfers/InLieu RechargeSSJ GSA
and OID
2019-2021 Drought 20,000
Dry 5,000
Normal -
Wet -
City of Lodi White
Slough Water
Pollution Control
Facility Expansion
Recycled
Water/In-Lieu
Recharge
City of Lodi 2019-2020 Drought 3,729
Dry 3,729
Normal 3,729
Wet 3,729
NSJWCD South
System
Modernization
In-Lieu
Recharge/Direct
Recharge
NSJWCD 2018-2024 Drought -
Dry 1,200
Normal 8,000
Wet 10,000
Direct Recharge NSJWCD 2022-2024 Drought -
ATTACHMENT 2
ESJ 2024 GSP Update 7 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Activity Project Type Project
Proponent
Schedule
(initiation
and
completion)
Baseline
Water
Year Type
Annual
Volume (AFY)
in PCBL-PMA
Version 3.0
and PCBL-CCPMA Version

3.0 NSJWCD
Tecklenburg
Recharge Project
Dry 300
Normal 1,000
Wet 2,000
NSJWCD South
System Groundwater
Banking with East
Bay Municipal
Utilities District
(EBMUD)
In-Lieu
Recharge
NSJWCD 2020-2025 Drought -
Dry 750
Normal 3,200
Wet 4,000
NSJWCD North
System
Modernization/Lakso
Recharge
In-Lieu
Recharge/Direct
Recharge
NSJWCD 2021-2026 Drought -
Dry 1,000
Normal 3,000
Wet 4,000
City of Stockton
Delta Water
Treatment Plant
Groundwater
Recharge
Improvements
Project
Direct Recharge City of
Stockton
2022-2026 Drought 5,040
Dry 5,040
Normal 5,040
Wet 5,040
NSJWCD Private
Pump Partnerships
In-Lieu/Direct
Recharge
NSJWCD 2024 Drought -
Dry -
Normal 1,500
Wet 3,000
OID In-Lieu and
Direct Recharge
Project
In-Lieu/Direct
Recharge
OID 2023-2032 Drought 0
Dry 0
Normal 3,000
Wet 3,000
ATTACHMENT 2
ESJ 2024 GSP Update 8 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Table 4: List of Category B Projects (2024)
Project Name Project Type Project
Proponent
Schedule (initiation
and completion)
Annual Volume
(AFY)
Perfecting Mokelumne
River Water Right
In-Lieu Recharge San
Joaquin
County
2024-2025 158,000
City of Manteca
Metering Infrastructure
Conservation City of
Manteca
Not determined 272
City of Lodi Surface
Water Facility
Expansion & Delivery
Pipeline
In-Lieu Recharge City of Lodi 2030-2033 4,750
BNSF Railway Company
Intermodal Facility
Recharge Pond
Direct Recharge CSJWCD 2020-2025 1,000
City of Stockton
Advanced Metering
Infrastructure
Conservation City of
Stockton
2023-2028 2,000
Manaserro Recharge
Project
Direct Recharge NSJWCD 2023-2025 8,000
City of Escalon
Wastewater Reuse
Recycling/
In-Lieu
Recharge/
Transfers
SSJ GSA 2020-2028 672
City of Ripon Surface
Water Supply
In-Lieu Recharge SSJ GSA 2028-2030 6,000
City of Escalon
Connection to Nick
DeGroot Water
Treatment Plant
In-Lieu Recharge SSJ GSA 2028-2030 2,015
Farmington Dam
Repurpose Project
Direct Recharge SEWD 2030-2050 60,000
Mobilizing Recharge
Opportunities (also
known as the “MICUP”
Project)
Direct Recharge San
Joaquin
County
2024-2040 158,000
NSJWCD Winery
Recycled Water
Recycling/
In-Lieu
Recharge/ Direct
Recharge
NSJWCD 2025-2027 750
ATTACHMENT 2
ESJ 2024 GSP Update 9 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Project Name Project Type Project
Proponent
Schedule (initiation
and completion)
Annual Volume
(AFY)
SSJID Storm Water
Reuse
Storm Water/
In-Lieu
Recharge/
Direct Recharge
SSJ GSA 2027-2030 1,100
North System
Groundwater Recharge
Project - Phase 2
Direct Recharge NSJWCD 2026-2029 3,000
Threfall Ranch
Reservoir, In-Lieu and
Direct Recharge Project
In-Lieu
Recharge/
Direct Recharge
ESJ GSA 2025 2,000
Wallace-Burson
Conjunctive Use
Program
Conjunctive
Use/Direct
Recharge
ESJ GSA 2030-2040 3,000
Calaveras River
Wholesale Water
Service Expansion
In-Lieu Recharge ESJ GSA 2020-2040 600
Recycled Water to
Manteca Golf Course
Recycling City of
Manteca
Not determined 406
Stormwater Collection,
Treatment, and
Infiltration
Direct Recharge/
Stormwater
City of
Manteca
Not determined Not determined
Off-Stream Regulating
Reservoir
Direct Recharge SEWD 2026-2050 Not determined
On-Farm Recharge
Project
Direct Recharge SEWD 2024-2030 108,300
Bellota Weir
Modifications Project
Direct
Recharge/Storm
water
SEWD 2023-2030 5,000
City of Stockton DWTP
Groundwater Recharge
- Design and
Construction
Direct Recharge City of
Stockton
2024-2026 11,000
Water Supply
Enhancement Project -
Distribution Pipelines
In-Lieu
Recharge/Direct
Recharge
SEWD 2024-2040 17,000
Water Treatment Plant
Aquifer Storage
Recovery Well - 7401
Direct Recharge SEWD 2024-2026 2,420
Beckman Well
Direct Recharge SEWD 2024-2028 Not determined
ATTACHMENT 2
ESJ 2024 GSP Update 10 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Project Name Project Type Project
Proponent
Schedule (initiation
and completion)
Annual Volume
(AFY)
West Linden Project In-Lieu
Recharge/Direct
Recharge
SEWD 2024-2035 60,000
Water Supply
Enhancement Project -
Direct Recharge
Direct Recharge SEWD 2024-2030 Not determined
SSJID Water Master
Plan - System
Improvements
In-Lieu Recharge SSJ GSA 2023-2040 15,000

1.3 Updated ESJWRM Version 3.0 Water Budget Tables
Table 5, Table 6, and Table 7 provide the updated ESJWRM Version 3.0 Water Budget Tables for the Stream System, Land Surface System and Groundwater System, respectively, for the Historical Conditions, Current Conditions, Projected Conditions Baseline (PCBL) and Projected Conditions Baseline with Climate Change.

Table 5: Average Annual Water Budget in ESJWRM Version 3.0 – Stream System (AF/year) Component
Historical
Conditions
(AF/year)
Current
Conditions
(AF/year)
Projected
Conditions
Baseline
(AF/year)
Projected
Conditions Baseline
With Climate
Change
(AF/year)
Hydrologic Period WY 1996 - 2023 WY 2019 - 2023 55 Years (WY 1969-2023)
55 Years
(WY 1969-2023)
with 2070 CT
Model Version
Historical
ESJWRM Version

3.0 Historical
ESJWRM Version

3.0 ESJWRM PCBL
Version 3.0

ESJWRM PCBL-CC
Version 3.0
Inflows
Stream Inflows1 4,221,000 4,224,000 4,519,000 4,929,000 Cosumnes River 385,000 432,000 463,000 501,000
Dry Creek 26,000 27,000 33,000 40,000
Mokelumne River 531,000 539,000 600,000 650,000
Calaveras River 163,000 186,000 184,000 207,000
Stanislaus River 613,000 665,000 664,000 809,000
San Joaquin River 2,427,000 2,315,000 2,500,000 2,635,000 Local Tributaries3 76,000 59,000 74,000 87,000
Stream Gain from Groundwater2 145,000 130,000 121,000 115,000 Eastern San Joaquin Subbasin 75,000 63,000 57,000 53,000 Dry Creek11- - - -
ATTACHMENT 2
ESJ 2024 GSP Update 11 Woodard & Curran, Inc.

Technical Memorandum No. 4: Water Budgets and Groundwater Storage November 2024 Component
Historical
Conditions
(AF/year)
Current
Conditions
(AF/year)
Projected
Conditions
Baseline
(AF/year)
Projected
Conditions Baseline
With Climate
Change
(AF/year)
Mokelumne River 14,000 13,000 10,000 8,000
Calaveras River 1,000 1,000 1,000 1,000
Stanislaus River 28,000 18,000 17,000 16,000
San Joaquin River 31,000 31,000 29,000 27,000
Other Subbasins4 70,000 67,000 65,000 62,000
Dry Creek 23,000 29,000 28,000 27,000
Mokelumne River11- - - -
Stanislaus River 27,000 19,000 17,000 16,000
San Joaquin River 20,000 20,000 19,000 18,000
Runoff to the Stream System5 629,000 741,000 656,000 753,000 Return Flow to Stream System6 96,000 95,000 111,000 112,000 Total Inflow10 5,092,000 5,190,000 5,407,000 5,908,000
Outflows
Stream Outflows7 4,426,000 4,469,000 4,655,000 5,108,000 Stream Seepage2 284,000 331,000 374,000 420,000
Eastern San Joaquin Subbasin 236,000 267,000 298,000 330,000 Dry Creek 2,000 2,000 2,000 2,000
Mokelumne River 125,000 135,000 150,000 160,000
Calaveras River 37,000 37,000 39,000 41,000
Stanislaus River 36,000 55,000 67,000 82,000
San Joaquin River 37,000 37,000 40,000 45,000
Other Subbasins4 47,000 65,000 76,000 90,000
Dry Creek 2,000 2,000 2,000 2,000
Mokelumne River 3,000 3,000 3,000 4,000
Stanislaus River 30,000 47,000 56,000 69,000
San Joaquin River 12,000 12,000 14,000 14,000
Surface Water Diversions8 340,000 353,000 340,000 340,000 Riparian Intake from Streams9 42,000 37,000 37,000 40,000 Total Outflow10 5,092,000 5,190,000 5,407,000 5,908,000 Notes:
1 Stream inflows into Eastern San Joaquin Subbasin include flows from Dry Creek, Mokelumne River, Calaveras River, Stanislaus River, San Joaquin River, and estimated tributary flows. Differences between historical and current/projected flows are due to differing hydrologic periods.

Manteca City CouncilApril 15, 2025

Manteca City Council
April 15, 2025