Eastern San Joaquin Groundwater Authority 1 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 TECHNICAL MEMORANDUM NO. 1 – Undesirable Result
Definition and Projects and Management Actions
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Matt Zidar, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Leslie Dumas, Sara Miller, and Lindsay Martien/Woodard & Curran DATE: June 24, 2022
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s November 18, 2021 Consultation Initiation Letter - Technical Memorandum 1, Response to DWR Deficiency No. 1 and Corrective Actions 1(a)-1(c)
1. Introduction
The Eastern San Joaquin Groundwater Authority (ESJGWA) received a Consultation Initiation Letter (Letter) on November 18, 2021 ( Attachment 1), from the California Department of Water Resources (DWR). The Letter identified two potential deficiencies with the Eastern San Joaquin Groundwater Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) which may preclude DWR’s approval, as well as potential corrective actions to address each potential deficiency. The Letter thus initiated consultation between DWR, the Plan Manager, and the Subbasin’s groundwater sustainability agencies (GSAs) regarding the amount of time needed to address the potential deficiencies and corrective actions. A subsequent meeting with DWR was held on April 4, 2022 to discuss the Subbasin’s proposed approach to addressing the identified deficiencies.
The analysis presented in this memorandum was completed in resp onse to the Letter, based on direction provided by the ESJGWA, the Subbasi n GSAs, and DWR. It is inten ded to supplement the Eastern San Joaquin GSP that was submitted in January 2020 and fill potential gaps identified in the Letter provided by DWR.
The following sections provide a response to Potential Corrective Actions 1(a) and 1(b), identified under Potential Deficiency 1. Per discussion with DWR staff, in adequately addressing Potential Corrective Action 1(a) and 1(b), Potential Corrective Action 1(c) is no longer applicable and will not need to be addressed by the GSAs.
Potential Deficiency 1
Potential Deficiency 1 relates to the GSP’s requirem ent of two consecutive non-dry (i.e., below normal, above normal, or wet) water year types and the exclusio n of dry and critically dry water-year types in the identification of undesirable results. It also requ ests additional detail on 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 2 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Potential Corrective Action 1 contains six subparts, 1( a) through 1(f). Potential Corrective Actions 1(a) and 1(b), the focus of this memorandum, are summarized be low. As stated above, Potential Corrective Action 1(c) is no longer applicable once 1(a) and 1(b) are addressed. Potential Corrective Actions 1(d) through 1(f) are addressed in separate technical memoranda.
Potential Corrective Action 1(a): The Letter states that DWR staff find the water year type requirement in the definition for undesirable results for groundwater levels (i.e., two consecutive non-dry years) to be “inconsistent with the objectives of SGMA”, and that this requirement could potentially allow for “unmanaged and continued lowering of groundwater levels under certain hydraulic and climatic conditions that have occurred historically”. As a Potential Corrective Action, the following is suggested: “The GSAs should remove the water year type requirement from the GSP’s undesirable result definition.”
Potential Corrective Action 1(b): The second part of this Potential Corrective Action seeks additional detail on how projects and management actions will offset drought-related groundwater reductions and avoid significant and unreasonable impacts. The Letter states that the GSP "fails to identify specific extraction and groundwater recharge management actions the GSAs would implement or otherwise describe how the Subbasin would be managed to offset...dry year reductions of groundwater stora ge”. As a Potential Corrective Action, the following is suggested:
“The GSP should be revised to include specific projects and management actions the GSAs would implement to offset drought year groundwater level declines.” The following sections provide a response to Potential Corrective Actions 1(a) and 1(b) and include a discussion of updated modeling work related to both Potential Corrective Actions. The purpose of this new analysis is to provide supplemental information, justification, and data n eeded to support the GSP and address each issue identified.
2. Removal of Water Year Type Requirement
In response to the comments provided by DWR in Potential Corrective Action 1(a), the ESJGWA has removed the non-dry water year type requirement from the definition of undesirable results for chronic lowering of groundwater levels, and, by proxy, for reduction of groundwater storage, land subsidence, and depletions of interconnected surface water. An updated redline strike out version of the GSP has been developed and adopted by the GSAs in response to this review. Relevant updated text is provided below.
Section 3.2.1.1.2. Identification of Undesirable Results (Chronic Lowering of Groundwater Levels)
An undesirable result is considered to occur during GSP implementation 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 lowering of groundwater levels during consecutive dry or critically-dry years is not considered to be unreasonable,
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 3 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 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.
Additional modeling, described in the sections below, demonstrates that the Subbasin is not projected to be in violation of its minimum thresholds with this updated definition of undesirable results once planned projects and management actions are in place.
3. Project and Management Actions Assumptions
As part of the process to respond to DWR, the ESJGWA worked with each GSA individually to update GSP project descriptions with new information that has become available in the past two years since the GSP was first adopted in 2020. These revised projects were divided into two categories: Category A projects (projects that are likely to advance in the next five years and have existing water rights or agreements) and Category B projects (projects that are not anticipated to advance in the next five years, but could be leveraged in the future, particularly if Category A projects do not fully achieve stated recharge and/or offset targets). Category B projects may be elevated to a Category A project should feasibility studies demonstrate a viable project, if water rights or contracts are firmly identified, if partnerships are formed, and if economic evaluation demonstrate that the projects are cost effective.
The analysis presented in this TM focuses on the simulation of implementation of Category A projects, which includes in lieu and direct recharge projects. Table 1 provides a list of these Category A projects, submitting GSA, project type, water source, and volume anticipated in each water year type. Table 2 provides a list of Category B projects for reference. Additional details, including water year type descriptions and updated project descriptions, assumptions, and Subbasin model results, can be found in Attachment 2.
In total, 11 Category A projects have been identified. Six are in-lieu recharge projects, three are direct recharge projects, and two 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 36,300 to 96,700 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 below. Additional surface water delivered to the Subbasin for agricultural uses: average of 39,700 AFY (range of 9,500-56,300 AFY)
Additional surface water delivered to the Subbasin for urban uses: 5,000 AFY or 20,000 AFY in only dry and drought years, respectively
Additional groundwater stored via direct groundwater recharge: average of 21,200 AFY (range of 6,500-32,000 AFY)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 4 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Table 1: Category A Projects
Project Submitting
GSA
Project
Type Water Source
Baseline
Water
Year Type
Annual
Volume
(AFY)
Notes
1. Lake Grupe In-Lieu
Recharge
Stockton
East Water
District
In-Lieu
Recharge
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.
Drought 2,000
Range of 0-2,000 AFY
in multiple dry years
Dry 4,900
Normal 4,900
Wet 4,900
2. SEWD Surface
Water
Implementation
Expansion
Stockton
East Water
District
In Lieu
Recharge
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.
Drought 4,000
Range of 0-4,000 AFY
in multiple drought
years
Dry 8,000
Normal 19,000
Wet 19,000
3. West Groundwater
Recharge Basin
Stockton
East Water
District
Direct
Recharge
This project relies on water from New Hogan
Reservoir (Calaveras River water) and New
Melones Reservoir (Stanislaus River water). This is
an existing surface wate r 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.
Drought 1,500
Dry 4,000
Normal 16,000
Wet 16,000
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 5 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Project Submitting
GSA
Project
Type Water Source
Baseline
Water
Year Type
Annual
Volume
(AFY)
Notes
4. CSJWCD Capital
Improvement
Program
Central San
Joaquin
Water
Conservation
District
In-Lieu
Recharge
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.
Drought 0
Dry 12,000
Normal 24,000
Wet 24,000
5. Long-Term Water
Transfer to SEWD
and CSJWCD
South San
Joaquin GSA
Transfers/I
n-Lieu
Recharge
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).
Drought 20,000
This project currently
only covers the transfer
of water from OID and
SSJID to SEWD urban
customers.
Dry 5,000
Normal 0
Wet 0
6. White Slough
Pollution Control
Facility Expansion
City of Lodi
Recycled
Water/In-
Lieu
Recharge
Treated wastewater efflue nt from White Slough
Water Pollution Control Facility.
Drought 3,729
Dry 3,729
Normal 3,729
Wet 3,729
7. NSJWCD South
System
Modernization
North San
Joaquin
Water
Conservation
District
In-Lieu
Recharge/
Direct
Recharge
This project relies on water from the Mokelumne
River. This is an existing water right held by
NSJWCD (Permit 10477).
Drought 0
Dry 0
Normal 4,800
Wet 6,000
8. NSJWCD
Tecklenburg
Recharge Project
North San
Joaquin
Water
Conservation
District
Direct
Recharge
This project relies on water from the Mokelumne
River. This is an existing surface water right held
by NSJWCD (Permit 10477).
Drought 0
Dry 1,000
Normal 4,800
Wet 6,000
Drought 0
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 6 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Project Submitting
GSA
Project
Type Water Source
Baseline
Water
Year Type
Annual
Volume
(AFY)
Notes
9. NSJWCD South
System Groundwater
Banking with
EBMUD
North San
Joaquin
Water
Conservation
District
In-Lieu
Recharge
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.
Dry 1,500
Normal 6,400 80% of wet year supply
Wet 8,000
10. NSJWCD North
System
Modernization/Lakso
Recharge
North San
Joaquin
Water
Conservation
District
In-Lieu
Recharge/
Direct
Recharge
This project relies on water from the Mokelumne
River. This is an existing surface water right held
by NSJWCD (Permit 10477).
Drought 0
Dry 1,000
Normal 3,200
Wet 4,000
11. Delta Water
Treatment Plant
Groundwater
Recharge
Improvements
Project Geotechnical
Investigation
City of
Stockton
Direct
Recharge
This project relies on raw water from the Delta
Water Treatment Plant.
Drought 5,040
Dry 5,040
Normal 5,040
Wet 5,040
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 7 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Table 2: Category B Projects
Project Name Project Type Submitting
GSA Current Status
Time-table
(initiation and
completion)
Annual
Volume
(AFY)
Perfecting Mokelumne River Water Right In-lieu Recharge San Joaquin County Planning phase 2022-2025 20,000 to
50,000
City of Manteca Advanced Metering
Infrastructure Conservation City of
Manteca
Currently
underway 2019-2021 272
City of Lodi Surface Water Facility Expansion &
Delivery Pipeline In-lieu Recharge City of Lodi Planning phase 2030-2033 4,750 BNSF Railway Company Intermodal Facility
Recharge Pond Direct Recharge CSJWCD Planning phase 2020-2023 1,000 City of Stockton Advanced Metering
Infrastructure Conservation City of
Stockton
Initial study
completed in
2011
2020/25-
2025/28 2,000
Manaserro Recharge Project Direct Recharge NSJWCD Planning phase 2019-2022* 8,000 City of Escalon Wastewater Reuse
Recycling/
In‑lieu Recharge/
Transfers
SSJ GSA Planning phase 2020-2028 672
City of Ripon Surface Water Supply In-lieu Recharge SSJ GSA Design complete;
environmental
permitting
underway
2020-2024 6,000
City of Escalon Connection to Nick DeGroot
Water Treatment Plant In-lieu Recharge SSJ GSA
Conceptual
design phase;
environmental
review complete
2020-2023 2,015
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 8 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Project Name Project Type Submitting
GSA Current Status
Time-table
(initiation and
completion)
Annual
Volume
(AFY)
Farmington Dam Repurpose Project Direct Recharge SEWD
Preplanning
phase with
reconnaissance
study complete
2030-2050 30,000
Recycled Water Transfer to Agriculture
Recycling/Transfer
s/
In‑lieu Recharge
City of
Manteca
Planning phase
with evaluation
completed in
Draft Reclaimed
Water Facilities
Master Plan
Not
determined 5,193
Mobilizing Recharge Opportunities Direct Recharge San Joaquin County
Early conceptual
planning phase
Not
determined
Not
determined
NSJWCD Winery Recycled Water
Recycling/
In‑Lieu Recharge/
Direct Recharge
NSJWCD
Conceptual
planning and
discussion
2025-2027 750
Pressurization of SSJID Facilities Conservation SSJ GSA Feasibility study complete 2019-2030 30,000
SSJID Storm Water Reuse
Storm Water/
In-lieu Recharge/
Direct Recharge
SSJ GSA Planning phase 2027-2030 1,100
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 9 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
3.1 GSA Managed Water
All of the Category A projects included above are re charge projects (either direct or in-lieu) that have water available to complete the project through current water rights, contracts, or existing interagency agreements. The existing water rights in the Subbasin are included in Table 3 . These water rights are held and managed by individual agencies in the Su bbasin, and it would be up to the water rights holder to determine how much water was made available for any planned or future recharge projects, including the Category A projec ts. Though the total water available included in Table 3 reduces in drier water years, several agencies still have firm rights and contracts within their control aimed to maximize beneficial use in dry years when considering conjunctive use, banking, and groundwater storage projects. In addition to the total surface water rights included in Table 3, other supplies, such as stormwater runoff, recycled water, and water supplies from other agencies that may bank water in the subbasin in the future (e.g., EBMUD, Valley Water, etc.), may also be utilized for future Subbasin recharge projects. This water may be available for recharge by the GSAs that maintain and possess the water right. The water is currently, or is planned, for beneficial use by the holder, and GSAs are resp onsible for evaluating their high est and best use and how these supplies may be used to achieve sustainability.
Table 3: Total Current Water Rights and Contracts in Eastern San Joaquin Subbasin District/
Agency
Source
River/Reservoir Water Use Wet Year
Volume (AFY)1
Dry Year
Volume
(AFY)1
Comments
WID
Mokelumne/
Camanche
Reservoir
Agricultural/
M&I 60,000 39,000
Firm; Agreements with City
of Lodi and City of
Stockton
Agricultural/
M&I See note3 0 Non-firm
NSJWCD
Mokelumne/
Camanche
Reservoir
Agricultural/
M&I 20,000 0 Subject to EBMUD supply
and future requirements
City of
Stockton
Delta/ San
Joaquin River M&I 33,600 <33,600
Can take as much water as
is discharged by
wastewater treatment
plant
CCWD 2
Calaveras River Agricultural 1,900 1,900 Up to 43.5% of New Hogan yield (up to 30,928
of 71,100 AFY). Reduce by
7,800 AF if end of October
New Hogan storage is less
than 71,400 AF.
New Hogan
Reservoir M&I 2,700 2,700
SEWD
Calaveras/ New
Hogan
Reservoir2
Agricultural/
M&I 40,115 <40,115
56.5% of New Hogan
yield. Reduced by 10,000
AF if end of October New
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 10 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 District/
Agency
Source
River/Reservoir Water Use Wet Year
Volume (AFY)1
Dry Year
Volume
(AFY)1
Comments
Hogan storage is less than
71,400 AF.
Agricultural/
M&I 27,000 <27,000
Estimated unused portion
of CCWD’s up to 43.5%
New Hogan allocation
Stanislaus/ New
Melones
Reservoir
Agricultural/
M&I 75,000 <75,000
Interim, subject to other
users requirements and
availability
Stanislaus/ New
Melones
Reservoir
M&I 0 15,000
From agreement with
CSJWCD to receive first
15,000 AF of 49,000 AF
firm supply
CSJWCD
Stanislaus/ New
Melones
Reservoir Agricultural 80,000 34,000
49,000 AF firm supply,
31,000 AF interim supply
subject to other user’s
requirements
Stanislaus/ New
Melones
Reservoir
other user’s requirements
SSJID/
OID4
Stanislaus/ New
Melones
Reservoir
Agricultural/
M&I 600,000 <600,000
Includes agricultural use in
SSJID and OID. Includes
potential water sales to
SEWD/CSJWCD and other
out-of-district customers.
Includes agreement
between SSJID and City of
Escalon, City of Lathrop,
City of Manteca, and City
of Tracy.
CDWA Delta Agricultural 118,000 118,000 Estimated based on current demand within
Subbasin. SDWA Delta Agricultural 17,000 17,000
Notes:
1 The volumes in this table are not necessarily authoritative and are provided for general information purposes only. The actual quantity of water available from year to year and the quantity that is actually used vary significantly.
2 New Hogan Reservoir has an estimated “conservation storage” yield of 71,400 AFY. Stockton East Water District contract with the Bureau of Reclamation is for 56.5% of the yield, and Calaveras County Water District rights to the remaining 43.5%. CCWD currently uses approximately 3,500 AFY of its allocation.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 11 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Based on an agreement between CCWD and SEWD, SEWD currently has use of the unused portion of CCWD’s allocation.
3 Under the WID-EBMUD water right settlement agreement, 60,000 AFY is the firm portion of the Woodbridge Irrigation District water rights. 60,000 AFY is the minimum amount available to WID during any year when the inflow to Pardee Reservoir is greater than 375,000 AF. When the Pardee inflow is less than 375,000 AF, the minimum amount available to WID is 39,000 AFY. WID is entitled to divert water in excess of the 60,000 AFY under the priority of its water right licenses when such water is available at WID’s point of diversion and is surplus to EBMUD’s downstream commitments under the Joint Settlement Agreement. Through this water right, WID has agreements with City of Lodi and City of Stockton to provide raw water.
4 OID and SSJID share equally rights to 600,000 AFY when available. Of its 300,000 AFY share, OID provides water to its district area, of which about 40% is within the Eastern San Joaquin Subbasin and 60% is outside. SSJID is located completely within the Subbasin and has agreements to provide water to several cities both inside and outside the Subbasin (City of Escalon, City of Lathrop, City of Manteca, and City of Tracy). Both agencies participate in water transfers or sales to out-of-district deliveries, including SEWD and CSJWCD. In years when the full allotment is not available, the amount is less than 320,000 AFY and is based on a formula which is part of the agreement with USBR
4. Updated Modeling Work: Methods
The ESJGWA has performed updated projected water budget modeling and hydrograph analysis to identify: 1) where, when, and how often established minimum thresholds may be exceeded under projected conditions using the updated definition for undesirable results (with the water year type requirement removed from the definition), 2) what the impact of planned projects will have on the Subbasin groundwater storage deficit, 3) the amount of demand and pumping reduction to keep groundwater levels above the minimum thresholds, and 4) the potential effects of climate change.
Four scenarios were analyzed using the Eastern San Joaquin Water Resources Model (ESJWRM):
Projected Conditions Baseline (PCBL): This model run doesn’t include any projects or climate change. The PCBL represents long-term hydrologic conditions of the Subbasin under the foreseeable future level of development. The future level of development represents approximately Water Year (WY) 2040 or the closest information available from planning documents, and includes urban build out to either the sphere of influence or general plan boundaries. The model update documentation is included in Attachment 3. Projected Conditions Baseline with Climate Change (PCBL-CC): This model run is the same as the PCBL, but includes estimates of climate change in datasets for model stream inflows, precipitation, and evapotranspiration as provided by DWR. The model update documentation is included in Attachment 3.
Projected Conditions Baseline with Category A Projects (PCBL-PMA): This model is the same as the PCBL without climate change and includes the 11 Category A projects. The assumptions and results are included in Attachment 2.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 12 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Projected Conditions Baseline with Climate Change and Category A Projects (PCBL-CC- PMA): This model is the same as the PCBL -CC and includes climate change and the 11 Category A projects. The assumptions and results are included in Attachment 2.
For modeling purposes in this analysis, only projects designated as Category A were considered. For additional detail on the data and assumptions that went into this analysis, see Attachment 2 of this memorandum.
5. Updated Modeling Work: Results
5.1 Evaluating Impact of Projects on Groundwater Storage Deficit Modeling results indicate that the Category A projects, as currently estimated in Attachment 2, will resolve the Subbasin overdraft condition when im pacts due to climate change are not included.
Without projects, the modeling shows an average overdraft of 16,300 AFY over the 52 years of the PCBL simulation. With Category A projects in pl ace, the modelling shows a projected overdraft of -5,300 AFY on average in the PCBL-PMA (a negative number indicating the absence of an overdraft condition). The PCBL-PMA shows an average increase of 21,600 AFY of groundwater in storage when compared to the PCBL. Compared to the PCBL, with Category A projects modeled, the PCBL- PMA has 38,400 AFY less groundwater pumping due to in-lieu recharge projects, 24,500 AFY more recharge, and 28,900 AFY less stream seepage in to the groundwater syst em. Other hydrologic groundwater budget component differences are small between the PCBL and PCBL-PMA simulations.
While the groundwater storage def icit in the PCBL is projecte d to be corrected through the implementation of Category A projects as seen in PCBL-PMA, the modelin g shows that when climate change is factored in, th ere is still additional work (e.g., projects and/or management actions) that may need to be done to maintain subbasin sustainability. The PCBL water budget without projects and with climate change (PCBL-CC) shows a projected overdraft of 38,100 AFY.
When projects are added in, as simulated in PCBL -CC-PMA, this overdraft amount is reduced to 15,700 AFY, but still represents continuing groundwater overdraft in the Subbasin that is not sustainable.
5.2 Identifying Areas Where Groundwater Levels May Exceed Minimum Thresholds The groundwater level representative monitoring network well hydrographs were analyzed for the model runs completed to review th e potential impact to groundwater levels that the 52 years of varying hydrologic conditions and projected demands and supplies may have. The results below discuss the hydrographs for the PCBL, PCBL-CC, PCBL-PMA, and PCBL-CC- PMA and where, when, and how often the hydrographs exceed the minimum thresholds. A full description of the process, analysis, and results, along with all the repres entative monitoring network hydrographs, are included in Attachment 2.
In the PCBL without projects model run ( Figure 1), two representative monitoring network wells are projected to fall below their minimum thresholds (MT) for groundwater levels at some point in the 52-year projection:
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 13 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Well Swenson-3 exceeds its MT in 8 percent of total months or 15 percent of water years Well 01S10E04C001M exceeds its MT in 50 percent of total months or 79 percent of water years.
In the PCBL water budget scenario without projects, but with climate change factored in (PCBL-CC) (Figure 2), the modeling results show five representative monitoring network wells are expected to fall below their minimum thresholds at some point in the 52-year projection:
Well 01S09E05H002 exceeds its MT in 24 percent of total months or 33 percent of water years
Well Swenson-3 exceeds its MT in 8 percent of total months or 19 percent of water years Well #3 Bear Creek exceeds its MT in 8 perc ent of total months or 56 percent of water years
Well Hirschfeld [OID-8] exceeds its MT in 18 percent of total months or 25 percent of water years
Well 01S10E04C001M exceeds its MT in 82 percent of total months or 90 percent of water years).
These five wells exceeding their minimum thresholds demonstrates the need for planned projects and management actions that the ESJGWA will implement to recharge and/or offset groundwater to raise Subbasin groundwater levels.
When Category A projects are included in the ESJWRM, groundwater levels rise across the Subbasin, though the impact to levels varies from area to area. In the PCBL water budget scenario with projects included (PCBL-PMA) (Figure 3), projections show only one well falling below its minimum threshold for groundwater levels (Well 01S10E04C001M exceeds its MT in 8 percent of total months or 19 percent of water years) as compared to the two wells in the PCBL without Category A projects.
As seen with the five wells with exceedances in the PCBL-CC, the effect s of climate change could significantly impact Subbasin gr oundwater overdraft and groundwa ter levels. In the PCBL water budget scenario with projects and climate change fa ctored in (PCBL-CC-PM A), modeling results show three wells still falling below their minimum thresholds for groundwater in a 52-year projection:
Well 01S09E05H002 exceeds its MT in 1 percent of total months or 4 percent of water years Well Hirschfeld [OID-8] exceeds its MT in 1 percent of total months or 4 percent of water years
Well 01S10E04C001M exceeds its MT in 60 percent of total months or 79 percent of water years).
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 14 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 Notably, all three of these wells are clustered in the same area of the Subbasin, perhaps indicating the need for additional study or a targeted project or management action specific to this area.
Figure 1: Projected Conditions Baseline (PCBL) Water Budget Without Projects
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 15 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
Figure 2: Projected Conditions Baseline (PCBL) Water Budget Without Projects + Climate Change
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 16 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
Figure 3: Projected Conditions Baseline (PCBL) Water Budget With Projects
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 17 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
Figure 4: Projected Conditions Baseline (PCBL) Water Budget With Projects + Climate Change
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 18 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 An undesirable result for groundwater levels is defined as occurring when at least 25 percent of representative monitoring network wells used to monitor groundwater levels (5 of 21 wells in the Subbasin) fall below their minimum level threshold for two consecutive years. The consecutive year analysis for the model runs is covered in Attachment 2. The modeling results suggest that, with Category A projects implemented as planned, the Subbasin is not projected to see undesirable results within the planning timeframe of the GSP since neither model run with Category A projects has five wells with minimum threshold exceedances. However, given the undesirable result for groundwater levels projected to occur in five water years in the PCBL-CC, the GSAs need a plan to address potential minimum threshold exceedances where possible and adaptively manage around the uncertainty of climate change impacts on groundwater levels in the case that the Category A projects do not occur as anticipated.
5.3 Evaluating the Impact of Projects and Management Actions on Groundwater Levels During Dry Conditions
The hydrographs for the representa tive monitoring network wells tend to have the similar trends for when minimum threshold exceedances do occur. A full discussion of water year type conditions where exceedances occur is included in Attachment 2. According to the model results, minimum threshold exceedances occur in all water year types, though are less likely to occur in normal water years (above normal or below normal water years in the San Joaquin Valley Water Year Hydrologic Classification).
The 52 years of projected hydrology includes a range of hydrologic conditions, including three periods of multi-year droughts with at least two consecutive critical water years and surface water supplies reduced consistent to what occurred in WY 2015. Exceedances typically occur during or follow these multi-year drought periods. For the three wells with minimum threshold exceedances under climate change with Category A projects simulated (Well 01S09E05H002, Well Hirschfeld [OID-8], and Well 01S10E04C001M), Well 01S09E0 5H002 under the PCBL-CC-PMA exceeds its minimum threshold in September of Year 24 at the end of a sixth consecutive drought year and continues for two more months for three months to tal across two water years. It recovers during the following wet year and does n’t exceed again. Well Hirschfeld [OID-8] exceeds its minimum threshold at almost the same time (August of Year 24 toward the end of a sixth consecutive drought year) and continues for seven months in total across two water years before recovering. Therefore, in the case of these two wells, exceedances only occur after a prolonged drought period of just under six years. The last well, Well 01S10E04C001M, drops below its minimum threshold in the PCBL-CC-PMA in July of Year 8, which is the firs t of a two-year drought period. Though it comes above the minimum threshold for a few scattered months, it remains below the minimum threshold for eight consecutive water years (through Year 15) . In July of Year 21 with continuing drought conditions, the groundwater level drops below the minimum threshold again and remains below for the remainder of the simulation (33 consecutive water years), even though there are scattered months where the water level recovers above the minimum threshold.
The three wells described above only represent the wells that still exceed in the case of climate change and with Category A proj ects (in the PCBL-CC-PMA). Acro ss the five total wells with exceedances, the most typical time for exceedances is during or immediately after a multi-year
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 19 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022 drought. However, with project and managemen t actions implemented, the groundwater level undesirable results do not occur in any year.
6. Conclusions
In response to Potential Corrective Actions 1(a), the ESJGWA has removed the water year type requirement from the definition of undesirable results for chronic lowering of groundwater levels. In response to Potential Corrective Actions 1(b), the ESJGWA has evaluated the impact of project management actions on groundwater levels during drought conditions. As part of this work, the ESJGWA has developed an updated immediate and near-term (within next 5 years) plan for Category A project implementation and has performed modelling analyses to better understand these projects’ impact on avoiding minimum thresholds and undesirable results. Remaining projects are included in Category B (projects to be implemented longer-term) to be implemented in the case of Category A projects do not produce a response as simulated in the model and/or if additional recharge projects are required to achieve Subbasin sustainability by 2040. The GSAs are continuing to evaluate opportunities to increase supply reliability, resiliency, and efficiency, and projects may be added to the GSP priorities by the GWA as they become ready for decisions. The adaptive management strategy envisioned in the GSP is based on observation of groundwater levels, management objectives, minimum thresholds and triggers established by the GWA. The GWA is currently evaluating the funding and financing strategies that may be implemented with an eye towards an investment strategy. In addition, the ESJGWA has amended the GSP with actions and language to more specifically describe management actions that may be implemented as adaptive management measures if projects fall short of anticipated recharge and/or offset targets (See Adaptive Management actions described below). Key takeaways from these efforts are described below.
6.1 Conclusion 1: Removal of the Water Year Type Requirement Does Not Significantly Increase Projected Minimum Threshold Exceedances
In response to Potential Corrective Actions 1( a), the ESJGWA has removed the water year type requirement from the definition of undesirable results for the chronic lowering of groundwater levels. The modeling analyses, as described in the sections above, identified where, when, and how often established minimum thresholds may be exceeded under projected conditions. The modeling suggests that the removal of the water year requirement from the definition of undesirable results will not significantly increase the number of repr esentative monitoring network wells that exceed their minimum thresholds, and therefore, is no t anticipated to impact the Subbasin’s overall sustainability status and avoidance of undesirable results. The modeling also evaluated demand reduction and groundwater level responses to climate change for purposes of comparison.
By proxy, undesirable results are not anticipated for reduction in grou ndwater storage, land subsidence or depletions of inte rconnected surface water. The ch ronic lowering of groundwater levels minimum thresholds are determined to be protective of these three sustainability indicators by the same rationale as described in the GSP. The removal of the water year type requirement from the definition of undesirable results for gr oundwater levels is more protective than the definition previously provided in the GSP submitted in January 2020.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 20 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
6.2 Conclusion 2: With Climate Change, the Subbasin Will Likely Need to Implement Additional Projects and Management Actions
As noted previously, modelling indicates that a basin wide, average groundwater storage deficit of 15,700 AFY is anticipated under the effects of climate change, even after the implementation of Category A projects is simulated. While there is still much uncertainty around what the impacts of climate change may be, the ESJGWA should prepare for a continuing overdraft condition even with its Category A projects and will likely need to either cut back on groundwater use, add additional recharge projects, or access new or additional surface water supplies for in-lieu use. The Mokelumne River Water and Power Authority plans to perfect their Mokelumne River water right and build additional projects to utilize that water right, either by implementing previously identified projects such as those projects now in Category B or by developing new projects. Beyond this, alternative demand-side adaptive management actions will be considered as an alternative where necessary to achieve basin sustainability. Such actions could include fallowing of crops or mandatory demand reduction measures, as described below.
6.2.1 Adaptive Management Measures that may be Considered for Implementation GSP Section 6.4 Adaptive Management Strategies provides a high-level summary of the ESJGWA’s plans to evaluate additional supply-side and demand-side management actions if monitoring efforts demonstrate that the projects are not effective in achieving stated rechar ge and/or offset targets. However, based on comments from DWR requesting additional detail on management actions that could be implemented, the ESJGWA has developed descriptions of adaptive management measures to be considered for implementation if projects are demonstrated to not be effective in achieving Subbasin sustainability targets.
After implementation of the Category A projects, the adaptive management actions identified below could be implemented if additional measures are required to sustainably ma nage groundwater in the Subbasin.
These adaptive management actions are programs that are not currently ready for implementation, are in the early planning stages, and do not have a firm schedules for development but rather would be implemented as needed sometime after 2026 following reevaluation of Subbasin su stainability during the 5-Year GSP Update in 2025. The sections below descr ibe these potential programs as they are currently contemplated; none of these programs are planned for implementation in the Subbasin at this time.
6.2.1.1 Groundwater Extraction Fee with Land Use Modifications A groundwater extraction fee or groundwater production charge could be collected from entities that own or operate an agricultural well. Revenue from these fees could then be used to pay for a variety of activities such as the construction of water infrastructure, grou ndwater conservation initiatives, proper construction and destruction of wells to prevent contamination, groundwater recharge and recovery projects, purchase of imported water or other supplies to replenish the groundwater basin through direct or in-lieu recharge, and/or purchasing and permanent fallowing of marg inally-productive agricultural lands dependent on groundwater. Several agencies in California have already implemented such a program and have seen success in utilizing revenue to benefit the local groundwater basin. A similar methodology could be applied within the Eastern San Joaquin Subbasin.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 21 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
6.2.1.2 Rotational Fallowing or Permanent Fallowing of Crop Lands Agricultural water use can be temporarily reduced by fallowing crop lands. While this can have economic impacts to a region, the benefits may also include improved water supply reliability, improved groundwater quality, increased groundwater levels, reduced subsidence, and operational flexibility. Rotational fallowing of crop lands reduces the economic impacts to any one area by rotating the areas of fallowing. This management action could be combined with a recharge project through the application of surplus water supplies to the fallowed lands resulting in in-lieu groundwater recharge or the repurposing of the permanently fallowed lands to create wildlife habitat or some other land use benefit that is not reliant on groundwater as a supply. This management action could be implemented, if needed, to help the Subbasin work towards its sustainability goals. However, th e rules by which this management action would be implemented would have to be developed by the GSAs within the Subbasin.
6.2.1.3 Conservation Programming for Demand Reduction
A demand reduction measure serves to reduce water demand, surface water losses, and/or nonessential water uses. Demand reduction measur es may include a conservation ra te structure or a uniform rate structure with a conservation program that achi eves demand reduction. Conservation and demand management programs have been a priority for ut ility providers across the state for decades. Water conservation programs can by implemented by utilities to help offset the increasing demands being placed on water resources. Actions that may be considered a demand reduction measur e include, but are not limited to, the following activities:
Conservation rates
Water efficient landscaping
Smart meters
Water efficient fixtures and appliances
Water conservation education effort
Many of the GSAs in the Subbasin are currently implementing conservation programming for demand reduction. Under this ma nagement action, additional resources would be directed toward conservation programming for demand reduction such that these programs can be enhanced or expanded.
6.2.1.4 Mandatory Demand Reduction
To reduce groundwater demand to allow and encourage the recovery of the groundwater aquifer, mandatory demand reduction may be considered by the ESJGWA as needed to meet the sustainability needs of the Subbasin if projects and management actions fall short of reduction and offset targets.
Mandatory measures could include establishment of a per-acre groundwater allocation, metering, extraction reporting, land retirement, and other measures to ensure land is not in production. The proposed PMAs demonstrate that these mand atory demand reduction programs ar e not likely to be needed in the Eastern San Joaquin Subbasin and are a low priority. Se veral GSAs in critically overdrafted subbasins are implementing mandatory demand reductions as part of their sustainability efforts under SGMA.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 22 Woodard & Curran, Inc.
TM 1 - ESJ GSP Deficiency 1a-c Response_24Jun2022.docx June 2022
6.3 Conclusion 3: There Is a Need for Implementing Additional Projects or Management Actions in Focused Areas of The Subbasin
Modeling results indicate that, with Category A projects implemented as planned (in progress over the next five years and fully online prior to 2040), the Subbasin is not projected to see undesirable results related to chronic declines in groundwater levels within the planning timeframe of the GSP.
However, there are still certain representative mo nitoring network wells projected to exceed their minimum thresholds for groundwater levels period ically, both with and without climate change, especially following years of extreme drought conditions. The Subbasin will need to monitor these wells as project implementation moves forward to determine if the simulated trends are accurate.
Groundwater levels have been, and will continue to be, evaluated annually by the ESJGWA in order to monitor the levels against the chronic lowering of groundwater level minimum thresholds. These data are compiled and evaluated ea ch year as part of the data assessment and production of the Annual Report, submitted to DWR each April 1. Any groundwater level exceedances would be reviewed by a technical workgroup of the ESJGWA and elevated to the Steering Committee and ESJGWA Board for further consideration and action.
Even with Category A projects, the modeling suggests that potentially there are areas where one or more representative monitoring network wells are shown to exceed their minimum thresholds. For these areas, which are outside of the area of infl uence of existing Category A projects, there is a demonstrated need to implement a dditional projects or management actions from Category B, beyond the Category A projects that are anticipated, to address groundwater levels in this portion of the groundwater basin. Modelling suggests th at the benefits of projects and management actions to groundwater levels are most directly distributed locally to th e project area, further supporting this approach.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ATTACHMENT 1 – DWR Consultation Initiation Letter
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
November 18, 2021
Kris Balaji, PMP, P.E.
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 i nitiates
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. T he 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
determina
tion. 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 GSA s 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 GSA s should also provide a companion document with track ed changes of modifications made to address deficiencies. The GSA s 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 GSA s 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 GSA s 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
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 pot ential 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 h eading 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 G roundwater 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
qualitat
ive 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 GSA s, 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 e valuate 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 dr y water -year type s 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B 1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
• Chronic l
owering 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, t he 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 non- dry 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 classifications 15 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Department s
taff also find this methodology inconsistent with other portions of the GSP .
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 th e 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 GSA s 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 e limination of long -term overdraft conditions in the Subbasin. H owever, the GSP does not sufficient ly detail how projects and management actions, in conjunction with the proposed chronic lowering of groundwater levels sustainable management criteria, will o ffset 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 subsidence
19 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.2 1.3
1.4 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 T he 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 GS P states allows for operational flexibility .22 These minimum threshold values generally allow groundwater levels to decline below historic lows; minimum thresholds defined us ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.1 2
2.2 2.3
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 p rojects 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 GSA s 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 tota l 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 wit h a definition of undesirable result s 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 th eir 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.4 2.5
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
include an al
lowance 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 GSA s 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 achiev ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Potential Deficiency 2. The GSP does not provide enough information to support the use of the chronic lowering of g roundwater 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. H owever, 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 H owever, the GSP does not identify specific
infrastructure locations, particularly those associated with public saf ety, 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 s ubsidence, 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.1 3.2
3.3 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 driv ing 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, t he GSP is unclear on whether the conditions required to identify an undesirable result for chroni c 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 subsidence
34 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.4 3.5
3.6 3.7
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 suffic ient 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 preventati ve 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ATTACHMENT 2 – Assumptions and Results for Category A Projects in ESJWRM
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
TECHNICAL MEMORANDUM
TO: Eastern San Joaquin Groundwater Authority Technical Advisory and Legal/Policy Committees
PREPARED BY: Sara Miller and Jingnan Zhou (Woodard & Curran) REVIEWED BY: Leslie Dumas (Woodard & Curran)
DATE: June 2, 2022
RE: Assumptions and Results for Category A Projects in ESJWRM The goal of this technical memorandum is to document the Projects & Management Actions (PMAs) selected for simulation in the Eastern San Joaquin Water Resources Model (ESJWRM) , the assumptions made about potential project volumes and timing, and results of the model runs.
Initially, all the projects from the Eastern San Joaquin Groundwater Subbasin (ESJ Subbasin) Groundwater Sustainability Plan (GSP) and 2022 Sustainable Groundwater Management (SGM) Grant Program’s SGMA Implementation Round 1 application were considered. Based on updates in t he annual report and information from representatives of the Groundwater Sustainability Agencies (GSAs) in the Eastern San Joaquin Groundwater Basin Authority (ESJGBA) Technical Advisory Committee (TAC), 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 next 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 and individual meetings with the project proponents 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 13 projects. Two projects were removed due to a lack of information (project descriptions included in Appendix B) , for a total of 11 projects.
1. Background on Model
The Category A projects are added to the information in two existing model runs: the ESJWRM Projected Condition BaseLine (PCBL) Version 2.0 and Projected Condition BaseLine with Climate Change (PCBL-CC) Version 2.0 (Woodard & Curran, 2022). Both of these projected conditions model runs are different from the versions presented in the GSP (Version 1.0). The Version 2.0 PCBL and PCBL-CC were updated in 2022, following on the historical model update and recalibration completed in 2021 (Woodard & Curran, 2022).
The PCBL uses 52 years of hydrology data from water years (WY) 1969 through 2020 (October 1968 through September 30, 2020). The PCBL-CC uses all the same information as the PCBL, with changes to represent climate change conditions (2070 central tendency) impacting the stream inflows, evapotranspiration, and precipitation. The PCBL and PCBL-CC represent 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 docume nts.
The 52 years of the PCBL and PCBL-CC represent a range of hydrologic conditions, as identified by the water year types in the San Joaquin Valley Water Year Hydrologic Classification published by DWR, which classifies water years 1901 through 2020 as Wet (W), Above Normal (AN), Below Normal (BN), Dry (D), and Critical
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
(C) based on inflows to major reservoirs or lakes. A description of how this index is calculated and the specific data used to calculat e this index is available online from CDEC at http://cdec.water.ca.gov/cgi - progs/iodir/WSIHIST. To simplify assumptions for future level of development water supplies and demands included in the PCBL and PCBL -CC, the five San Joaquin Valley Water Year Hydr ologic Classification water year types were aggregated into three baseline water year types. 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).
To capture future extreme dry year periods with multiple dry years in the baseline where water supplies and demands were purposely reduced, the following 10 water years were designated as Drought periods: 1976- 1977, 1987 -1992, and 2014 -2015. These four baseline water year types are also described in the documentation for the updated PCBL (Woodard & Curran, 2022).
2. Category A Projects
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 conta ins a brief description of the proposed version of the project , which may have been updated since the description in the GSP or other documents , and any assumptions made in simulating the projects in ESJWRM. Since all volumes given below are annual, monthl y 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, though projects submitted by the same GSA are grouped together. 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, 11 Category A projects have been identified. Six are in -lieu recharge projects, three are direct recharge projects, and two are a combination of in -lieu recharge and direct recharge. Overall, the projects below include in-lieu recharge for agricultural use (7 projects) with deliveries excluding assumed losses with an average of 39,700 acre-feet per year (AFY) (ranging from 9,500-56,300 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 21,200 AFY (ranging from 6,500-32,000 AFY depending on baseline year type). Note that th ese project counts include those projects that include components of both in-lieu recharge and direct recharge.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 1: General Location of Category A Projects
2.1 Lake Grupe In-Lieu Recharge
Submitting GSA: Stockton East Water District (SEWD)
Project Source: GSP Project #1 (Chapter 6.2.4.1) and personal communication with Scot Moody (SEWD) and Justin Hopkins (SEWD) on April 21, 2022
Project Assumptions Confirmed By : Justin Hopkins (SEWD) on May 9, 2022 and Jeanne Zolezzi (Herum\Crabtree\Suntag) on May 12, 2022
Project Type: In-Lieu Recharge
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 1,750 acres of orchards surrounding Lake Grupe in SEWD
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 multiple farms/growers currently using groundwater. The project is to allow about 1,750 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 then the surrounding growers would pump the water from the Lake for irrigation. The benefit of this project is the in-lieu banking of groundwater from irrigation conversion with very little losses assumed in the transport and delivery of the water. This project is currently in construction and should be operational in 2022.
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 volu me of water delivered was assumed by multiplying 1,750 acres 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
2.2 SEWD Surface Water Implementation Expansion
Submitting GSA: Stockton East Water District (SEWD)
Project Source: GSP Project #2 (Chapter 6.2.4.2) and personal communication with Scot Moody (SEWD) and Justin Hopkins (SEWD) on April 21, 2022
Project Assumptions Confirmed By : Justin Hopkins (SEWD) on May 9, 2022 and Jeanne Zolezzi (Herum\Crabtree\Suntag) on May 12, 2022
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 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 153 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 1,048 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
2.3 West Groundwater Recharge Basin
Submitting GSA: Stockton East Water District (SEWD)
Project Source : Project not included in GSP. Added based on information provided by personal communication with Scot Moody (SEWD) and Justin Hopkins (SEWD) on April 21, 2022.
Project Assumptions Confirmed By: Justin Hopkins (SEWD) on May 9, 2022 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. The project is currently in the design stage with first phase construction beginning summer 2022 and is estimated to be completed in approximately 2032.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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
2.4 CSJWCD Capital improvement Program
Submitting GSA: Central San Joaquin Water Conservation District (CSJWCD) Project Source: GSP Project #6 (Chapter 6.2.4.6) and personal communication with Reid Roberts (CSJWCD) on April 26, 2022
Project Assumptions Confirmed By: Reid Roberts (CSJWCD) on May 6, 2022 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 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 about an estimated 25-30% of the water on t he 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
2.5 Long-term Water Transfer to SEWD and CSJWCD
Submitting GSA: South San Joaquin GSA
Project Source: GSP Project #8 (Chapter 6.2.4.8) and personal communication with Justin Hopkins (SEWD), Eric Thorburn (Oakdale Irrigation District or OID), Reid Roberts (CSJWCD), and Brandon Nakagawa (South San Joaquin Irrigation District or SSJID) on April 25, 2022.
Project Assumptions Confirmed By : Justin Hopkins (SEWD) on May 9, 2022 and Emily Sheldon (Oakdale Irrigation District or OID) on May 9, 2022
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 S an 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 Sub basin. 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 o f 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. Additional infrastructure may be necessary to increase distribution of surface water supplies to irrigated agriculture and to achieve adequate improvement toward sustainability goals.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 p roviding 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 rece ive 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 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)
2.6 White Slough Water Pollution Control Facility Expansion Submitting GSA: City of Lodi
Project Source: GSP Project #5 (Chapter 6.2.4.5) and personal communication with Travis Kahrs and Charles Swimley (City of Lodi) on April 25, 2022
Project Assumptions Confirmed By: Travis Kahrs (City of Lodi) on May 11, 2022
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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
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. This project is estimated to reduce the annual volume discharged to Dredger Cut (a dead-end slough of the Sacramento-San Joaquin River Delta) by approximately 160 to 210 million gallons.
Flow will be diverted from Dredger Cut at a rate up to 1,700 gallons per minute over an approximate 75- to 90-day period be tween 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 Study 2 (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 about 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
2.7 NSJWCD South System Modernization
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source : GSP Project #7 (Chapter 6.2.4. 7) and personal communication with Jennifer Spaletta (Spaletta Law PC) and Daniel de Graaf (de Graaf Engineering) on April 18, 2022 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022 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. Water would come from NSJWCD Permit 10477 supplies, which are available in about 55 percent of years. Environmental review for the project is complete and funding has been sought and a landowner improvement district has been formed.
Project Volume:
The volumes for the project tabulated below were provided by Jennifer Spaletta on April 21, 2022 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 Pr oject). 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 by 2035.
The volumes below assume NSJWCD uses its full water right of 20,000 AFY between all of its projects in wet years, 80% of the 20,000 AFY or 16,000 AFY in normal years, and very limited quantities in dry years.
Appendix A includes the numbers provided by Jennifer Spaletta, which also includes edits to the existing CAL FED groundwater recharge project and the Tracy Lake recharge project as part of NSJWCD utilizing more of its existing water right.
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 1,000 0 1,000
Normal 9,600 4,800 4,800
Wet 12,000 6,000 6,000
2.8 NSJWCD Tecklenburg Recharge Project
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source : GSP Project #14 (Chapter 6.2.5.6) and personal communication with Jennifer Spaletta (Spaletta Law PC) and Daniel de Graaf (de Graaf Engineering) on April 18, 2022 Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022 Project Type: Direct Recharge
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 is investigating constructing and operating a 10 -acre recharge pond o n the south side of the Mokelumne River on property owned by the Tecklenburg family through a purchase.
NSJWCD would use Permit 10477 water available during 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.
Project Volume:
The volumes for the project tabulated below were provided by Jennifer Spaletta on April 21, 2022 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 by 2035.
The volumes below assume NSJWCD uses its full water right of 20,000 AFY between all of its projects in wet years, 80% of the 20,000 AFY or 16,000 AFY in normal years, and very limited quantities in dry years.
Appendix A includes the numbers provided by Jennifer Spaletta, which also includes edits to the existing CAL FED groundwater recharge project and the Tracy Lake recharge project as part of NSJWCD utilizing more of its existing water right.
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 1,000 0 1,000
Normal 9,600 4,800 4,800
Wet 12,000 6,000 6,000
2.9 NSJWCD South System Groundwater Banking with EBMUD
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source : GSP Project #11 (Chapter 6.2. 5.3) and personal communication with Jennifer Spaletta (Spaletta Law PC) and Daniel de Graaf (de Graaf Engineering) on April 18, 2022 Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022 Project Type: In-Lieu Recharge
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 rights protests. The PDA Agreement includes a commitment to undertake a p ilot-level groundwater ba nking project and a longer -term groundwater baking project. The pilot level banking project is called the “DREAM” project and is already underway. The DREAM project involves the delivery of 1,000 AF of EBMUD water into the NSJWCD s ervice area along the South System to use for irrigation, effectuating 1,000 AF of in -lieu groundwater recharge.
EBMUD will receive a banked water credit of 50 percent of the amount of water recharge, not to exceed 500 AF. EBMUD can withdraw the banked water credit in the future. NSJWCD will control the withdrawal of the banked water by pumping groundwater from a well that is centrally located in the area of recharge and then conveying the pumped groundwater to the EBMUD Mokelumne Aqueduct. The extraction a nd return of the banked water are subject to a San Joaquin County groundwater export permit. The permit places additional conditions and restrictions on the extraction of the banked water, including a 5 percent per year annual loss factor and pumping restrictions to prevent impacts to other groundwater users.
EBMUD and NSJWCD have started the preliminary planning for the longer -term banking project. The longer-term banking project may 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 in-lieu recharge within NSJWCD, and to extract and return banked water credits to EBMUD. These surface water supplies would come from EBMUD’s water rights on the Mokelumne Ri ver and would be in addition to surface water available under NSJWCD’s water right. EBMUD would receive a banked water credit for 50 percent 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 percent annual loss factor in the San Joaquin County export ordinance.
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 April 21, 2022. In wet and normal years, about 50% of the water will be used for agricultural purposes and 50% for recharge. In critical years, no water is available and i n dry years, all of the water is expected to be used for recharge projects. An agreement is in place and parties need finalize design. Environmental review and permitting are still needed. NSJWCD and EBMUD are currently working to complete the pilot DREAM project. Facilities to complete the final phases of the pilot project are currently under construction and are expected to be completed by early 2022. Planning efforts for a larger scale banking project are underway. The project is expected to be 50% built out by 2028 and fully built out by 2035. EBMUD will receive a banked water credit of 50% of amount recharged, not to exceed 500 AF.
Appendix A includes the numbers provided by Jennifer Spaletta, which also includes edits to the existing CAL FED groundwate r recharge project and the Tracy Lake recharge project as part of NSJWCD utilizing more of its existing water right.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Baseline Water
Year Type
Annual Volume
(acre-feet per
year or AFY)
Notes
Drought 0
Dry 1,500
Normal 6,400 80% of Wet year supply
Wet 8,000
2.10 NSJWCD North System Modernization/Lakso Recharge
Submitting GSA: North San Joaquin Water Conservation District (NSJWCD) Project Source : GSP Project #12 (Chapter 6.2.5.4), 2022 SGM Implementation Grant Program Round 1 application, and personal communication with Jennifer Spaletta (Spaletta Law PC) and Daniel de Graaf (de Graaf Engineering) on April 18, 2022
Project Assumptions Confirmed By: Jennifer Spaletta (Spaletta Law PC) on May 4, 2022 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 surface water to farmers in -lieu of groundwater pumping and surface water for direct and Flood MAR recharge in the non -irrigation season. Water would come from NSJWCD Permit 10477 supplies, which are available in about 55 percent of years. The Lakso vineyard is located along the existing North System pipeline and includes very sandy soils that a re 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.
Project Volume:
The volumes for the project tabulated below were provided by Jennifer Spaletta on April 21, 2022. In wet and normal years, about 50% of the water will be used for agricultural purposes and 50% for recharge (likely via the Lakso Recharge Project). In critical years, no water is available and in dry years, all of the water is expected to be used for recharge pr ojects. The project is expected to be 50% built out by 2028 and fully built out by 2035.
The volumes below assume NSJWCD uses its full water right of 20,000 AFY between all of its projects in wet years, 80% of the 20,000 AFY or 16,000 AFY in normal years, and very limited quantities in dry years.
Appendix A includes the numbers provided by Jennifer Spaletta, which also includes edits to the existing CAL FED groundwater recharge project and the Tracy Lake recharge project as part of NSJWCD utilizing more of its existing water right.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Baseline Water
Year Type
Annual Volume
(acre-feet per
year or AFY)
Notes
Drought 0
Dry 1,000
Normal 3,200
Wet 4,000
2.11 Delta Water Treatment Plant Groundwater Recharge Improvements Project Geotechnical Investigation
Submitting GSA: City of Stockton
Project Source : GSP Project #20 (Chapter 6.2. 6.3), 2022 SGM Implementation Grant Program Round 1 application, and personal communication with Mel Lytle (City of Stockton), Eric Houston (City of Stockton), and Mitchell Maidrand (City of Stockton) on April 21, 2022 Project Assumptions Confirmed By : Received no response to draft assumptions sent out on May 3, 2022 and May 24, 2022
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 throug h 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 confir m 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.
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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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.
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 availabl e 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 AF Y 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 petition 2, 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
3. Results of Category A Projects in ESJWRM
This section provides a summary of the ESJ Subbasin ESJWRM 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) model results. 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Both models 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 11 Category A PMAs simulated as additional diversions in both PCBL-PMA and PCBL-CC- PMA models is provided in Table 1, along with fractions for recoverable loss (i.e., percolation or canal seepage), non-recoverable loss (i.e., evaporation), and delivery (i.e., amount delivered is equal to the t otal amount minus the recoverable and non-recoverable losses). The remaining 66 PCBL and PCBL-CC diversions are summarized in a separate document (Woodard & Curran, 2022).
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 1: Summary of ESJWRM Category A Projects Surface Water Deliveries ID Description Diversion
Location Delivery Area Primary
Use
Fraction Average Annual
Diversion*** (acre-
feet) RL* NL** Delivery
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% 13,400
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% 20,300
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% 11,500
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% 100% 3,700
73 North San Joaquin WCD
South System
Modernization
Mokelumne
River NSJWCD South System Ag 50% 0% 50% 5,500
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction Average Annual
Diversion*** (acre-
feet) RL* NL** Delivery
74 North San Joaquin WCD
Tecklenburg Recharge
Project
Mokelumne
River
Recharge basin located
in NSJWCD South
System
Recharge 100% 0% 0% 4,100
75 North San Joaquin WCD
South System
Groundwater Banking
with EBMUD
Mokelumne
River NSJWCD South System Ag 50% 0% 50% 5,600
76 North San Joaquin WCD
North System
Modernization/Lasko
Recharge
Mokelumne
River NSJWCD North System Ag 50% 0% 50% 2,600
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
*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)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.1 Projected Conditions Baseline with Category A Projects and Management Actions The section below summarizes the results for the PCBL -PMA as compared to the PCBL. Neither of these runs include climate change.
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 water demand for the Subbasin within the 52 -year simulation period is 1,256,100 acre-feet per year (AFY), consisting of approximately 1, 098,000 AFY of agricultural demand and 158,100 AFY of urban demand. This demand is met by an annual average of 5 71,100 AFY of surface water deliveries (490,400 AFY of agricultural and 80,700 AFY of urban deliveries) and is supplemented by 704,400 AFY of groundwater prod uction (627,200 AFY of agricultural and 77,200 AFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 19,600 AFY 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 proj ected 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 2. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 2Error! Reference source not found. and Error! Reference source not found. for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.
Table 2 also includes the PCBL results and a Category A projects benefit calculated as the PCBL-PMA results minus the PCBL results. The PCBL -PMA has an average of 37,600 AF Y more surface water for agricultural purposes and 5,100 AF Y more surface water for urban areas compared to the PCBL. For urban areas, this represents a comparable reduction in groundwater pumping of 5,000 AF Y. For agricultural areas, the increased surface water results in 33,400 AFY 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 2: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Comparison Between the PCBL (Version 2.0) and the PCBL-PMA
Land and Water Use Budget Component
Annual Average
PCBL
(Version
2.0)
PCBL-PMA
PMA Benefit
(PCBL-PMA
minus PCBL)
Agricultural Area (thousand acres) 359 359 0
Agricultural Demand (AFY) 1,099,900 1,098,000 -1,900
Agricultural Groundwater Pumping (AFY) 660,600 627,200 -33,400 Agricultural Surface Water Deliveries (AFY) 452,800 490,400 37,600 Agricultural Shortage (AFY)1 -13,500 -19,600 -6,100
Urban Area (thousand acres) 153 153 0
Urban Demand (AFY) 158,100 158,100 0
Urban Groundwater Pumping (AFY) 82,200 77,200 -5,000
Urban Surface Water Deliveries (AFY) 75,600 80,700 5,100 Urban Shortage (AFY)1 300 200 -100
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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 2: Eastern San Joaquin Subbasin Projected Agricultural Demand in the PCBL-PMA
Figure 3: Eastern San Joaquin Subbasin Projected Urban Demand in the PCBL-PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 remains the largest component in the groundwater budget with an annual average 712,900 AFY. The PCBL-PMA offsets this pumping with 290,100 AFY of deep percolation, a net gain from stream of 1 51,800 AFY, 186,200 AFY of other recharge, and a total subsurface inflow of 90,100 AFY.
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 c alibration, 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 -PMA is -5,300 AFY, with the negative sign actually indicating an absence of groundwater overdraft and an increase in storage over the 52 years of the PCBL-PMA. These annual averages are shown in Table 3. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 4.
Table 3 also includes the PCBL results and a Category A projects benefit calculated as the PCBL-PMA results minus the PCBL results . The results indicate that the Category A projects will resolve the PCBL Subbasin overdraft condition when impacts due to climate change are not included. Without projects, the modeling shows an average overdraft of 16,300 AFY over the 52 years of the PCBL simulat ion. With Category A projects in place, the modelling shows a projected overdraft of -5,300 AFY on average in the PCBL -PMA.
The PCBL-PMA shows an average increase of 21,600 AFY of groundwater in storage when compared to the PCBL. Compared to the PCBL, with Category A projects modeled, the PCBL -PMA has 38,400 AFY less groundwater pumping due to the new in-lieu recharge projects, 24,500 AFY more recharge (both direct recharge projects and canal seepage losses for the in -lieu recharge projects) , and 28,900 AFY less stream seepage into the groundwater system due to higher groundwater levels . Other hydrologic groundwater budget component differences are small between the PCBL and PCBL-PMA simulations.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 3: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL (Version 2.0) and the PCBL-PMA Hydrologic Groundwater Budget
Component
Annual Average
PCBL
(Version 2.0) PCBL-PMA
PMA Benefit
(PCBL-PMA
minus PCBL)
Deep Percolation (AF) 282,100 290,100 8,000
Other Recharge (AF) 161,700 186,200 24,500
Net Stream Seepage (AF) 180,700 151,800 -28,900
Net Boundary Inflow (AF) 110,400 90,100 -20,300
Groundwater Pumping (AF) 751,300 712,900 -38,400
Change in Groundwater Storage (AF) 16,300 -5,300 -21,600
Figure 4: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget in the PCBL - PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 as compared to the PCBL-CC.
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 water demand for the Subbasin within the 52 -year simulation period is 1,337,800 AFY, consisting of approximately 1,179,700 AFY of agricultural demand and 158,100 AFY of urban demand. This demand is met by an annual average of 570,700 AFY of surface water deliveries (490,200 AFY of agricultural and 80,500 AFY of urban deliveries) and is supplemented by 7 85,600 AFY of groundwater production (708,400 AFY of agricultural and 77,200 AFY of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is about 19,000 AFY 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 (g roundwater 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 4. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 5 and Figure 6 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.
Table 4 also includes the PCBL-CC results and a Category A projects benefit calculated as the PCBL-CC-PMA results minus the PCBL-CC results. The PCBL-CC-PMA has an average of 37,800 AFY more surface water for agricultural purposes and 5, 000 AFY more surface water for urban areas compa red to the PCBL -CC. For urban areas, this represents an equivalent reduction in groundwater pumping of 5,000 AFY. For agricultural areas, the increased surface water results in 34,000 AFY less groundwater pumping, a number smaller than the amount of surfac e 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 and PCBL -CC-PMA 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 2 and Table 4.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 4: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Comparison Between the PCBL-CC and the PCBL-CC-PMA
Land and Water Use Budget
Component
Annual Average
PCBL-CC PCBL-CC-PMA
PMA Benefit
(PCBL-CC-PMA
minus PCBL-CC)
Agricultural Area (thousand acres) 359 359 0
Agricultural Demand (AF) 1,181,300 1,179,700 -1,600
Agricultural Groundwater Pumping (AF) 742,400 708,400 -34,000 Agricultural Surface Water Deliveries (AF) 452,400 490,200 37,800 Agricultural Shortage (AF)1 -13,500 -18,900 -5,500
Urban Area (thousand acres) 153 153 0
Urban Demand (AF) 158,100 158,100 0
Urban Groundwater Pumping (AF) 82,200 77,200 -5,000
Urban Surface Water Deliveries (AF) 75,500 80,500 5,000 Urban Shortage (AF)1 400 400 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 5: Eastern San Joaquin Subbasin Projected Agricultural Demand in the PCBL -CC-PMA
Figure 6: Eastern San Joaquin Subbasin Projected Urban Demand in the PCBL-CC-PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 surroun ding 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 remains the largest component in the groundwater budget with an annual average 794,100 AFY. The PCBL-CC-PMA offsets this pumping with 293,000 AFY of deep percolation, a net gain from stream of 189,800 AFY, 189,900 AFY of other recharge, and a total subsurface inflow of 1 05,700 AFY annually. The cumulative change in groundwater storage can be calcula ted 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 -CC-PMA is 15,700 AFY, 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 5. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure 7.
Table 5 also includes the PCBL results and a Category A projects benefit calculated as the PCBL-PMA results minus the PCBL results . While the groundwater storage deficit in the PCBL is projected to be corrected through the implementation of Category A projects as seen in PCBL -PMA, the modeling shows that when climate change is factored in for the PCBL -CC-PMA, 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 has a projected overdraft of 38,100 AFY. When projects are added in, as simulated in PCBL-CC-PMA, this overdraft amount is reduced to 15,700 AFY, but still represents continuing groundwat er overdraft in the Subbasin that is not sustainable.
Compared to the PCBL -CC, with Category A projects modeled, the PCBL -CC-PMA has 39,000 AFY less groundwater pumping due to the new in-lieu recharge projects, 24, 600 AFY more recharge (both direct recharge projects and canal seepage losses for the in -lieu recharge projects) , and 28, 300 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-CC-PMA simulations.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 5: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL-CC and the PCBL-CC-PMA
Hydrologic Groundwater Budget
Component
Annual Average
PCBL-CC PCBL-CC-PMA
PMA Benefit
(PCBL-CC-PMA
minus PCBL-CC)
Deep Percolation (AF) 285,600 293,000 7,400
Other Recharge (AF) 165,300 189,900 24,600
Net Stream Seepage (AF) 218,100 189,800 -28,300
Net Boundary Inflow (AF) 126,000 105,700 -20,300
Groundwater Pumping (AF) 833,100 794,100 -39,000
Change in Groundwater Storage (AF) 38,100 15,700 -22,400
Figure 7: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget in the PCBL-CC- PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.3 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 8 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.
Figure 8: Groundwater Level Representative Monitoring Well Locations
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 and PCBL-CC-PMA as compared to the PCBL and PCBL -CC, respectively . Five representative monitoring network wells ( Well 01S09E05H002, Well Swenson-3, Well #3 Bear Creek , Well Hirschfeld (OID8) , and Well 01S10E04C001) reported groundwater
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
levels below their minimum thresholds for at least one month in any of the models evaluated (PCBL, PCBL- PMA, PCBL-CC, and PCBL-CC-PMA). The hydrographs of these five representative monitoring network wells are shown and discussed in Sections 3.3.1 and 3.3.2. The hydrographs for all of the 21 representative monitoring network wells are included in Appendix C. Subbasin undesirable results for groundwater levels are discussed in Section 3.3.3.
3.3.1 Projected Conditions Baseline without and with Category A Projects and Management Actions
Figure 9 shows the location of the two representative monitoring network wells (Well Swenson-3 and Well 01S10E04C001) with groundwater levels below their minimum thresholds at some any in the 52 -year projection of the PCBL (without climate change or Category A projects). Figure 10 shows the location of the one representative monitoring network well (Well 01S10E04C001) with groundwater levels below its MT in the PCBL-PMA.
Figure 11 shows the hydrograph of Well Swenson-3 and
Figure 12 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 (solid blue line), PCBL-PMA (dotted blue line), PCBL-CC (solid brown line), PCBL -CC-PMA (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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 9: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 10: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 11: Groundwater Level Hydrograph for Well Swenson-3
Figure 12: Groundwater Level Hydrograph for Well 01S10E04C001
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Under the PCBL (without climate change or Category A projects), both representative monitoring network wells with hydrographs shown above in Figure 11 and
Figure 12 (Well Swenson-3 and Well 01S10E04C00) exceed their minimum thresholds The text below discusses when and how often MT exceedances occur for the two wells:
• Well Swenson-3:
o Exceeds its MT in 48 months out of a total of 624 months (8% of all months) or 8 water years out of a total of 52 water years (15% of all water years). o The exceedances occur in October of Year 10 after 2 consecutive drought years, in July of Year 21 after 2 consecutive drought years with exceedances continuing for 5 consecutive water years in total, and in June of Year 47 after one drought year with exceedances continuing for 2 consecutive water years total.
• Well 01S10E04C00:
o Exceeds its MT in 314 months out of a total of 624 months (50% of all months) and 41 water years out of a total of 52 water years (79% of all water years). o The exceedances occur in August of Year 8 in a drought year with exceedances continuing for 8 consec utive water years in total, and in August of Year 20 after a drought year with exceedances continuing for the remainder of the PCBL (33 consecutive water years in total).
Under the PCBL with Category A projects (PCBL-PMA), only one representative monitoring network well (Well 01S10E04C00 shown in
Figure 12) exceeds its MT.
• Well 01S10E04C00:
o Exceeds its MT in 51 months out of a total of 624 months (8% of all months) and 10 water years out of a total of 52 water years (19% of all water years). o The exceedances occur in August of Year 10 after 2 consecutive drought years , in September of Year 22 after 3 consecutive drought years with exceedances continuing for 8 consecutive water years in total, and in July of Year 48 after 2 consecutive drought years.
As discussed in Section 3.1.2, 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 water budget scenario with projects included (PCBL -PMA), projections show only one well falling below its minimum threshold for groundwater levels as compared to the two wells in the PCBL without Category A projects. In other words, the Category A projects caused one well that was exceeding its MT in the PCBL to no longer exceed its MT the PCBL-PMA. This well, located in the City of Stockton , has groundwater levels increasing due to the Category A projects occurring nearby.
3.3.2 Projected Conditions Baseline with Climate Change and without and with Category A Projects and Management Actions
Figure 13 shows the location of the five representative monitoring network wells (Well 01S09E05H002, Well Swenson-3, Well #3 Bear Creek , Well Hirschfeld (OID8) , and Well 01S10E04C001) with projected groundwater levels falling below their MTs for groundwater levels at any point in the 52-year projection of the PCBL with climate change and without Category A projects (PCBL-CC). Figure 14 shows the location of
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
the three representative monitoring network wells (Well 01S09E05H002, Hirschfeld (OID8) , and Well 01S10E04C001) with groundwater levels falling below their MTs in the PCBL with climate change and with Category A projects (PCBL-CC-PMA).
Figure 15 shows the hydrograph of Well 01S09E05H002,
Figure 16 shows the hydrograph of Well #3 Bear Creek, and Figure 17 shows the hydrograph of Well Hirschfeld (OID8). The hydrographs for the other wells exceeding their MTs in the PCBL-CC and PCBL-CC- PMA were shown above in Figure 11 and
Figure 12. 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 (solid blue line), PCBL -PMA (dotted blue line), PCBL -CC (solid brown line), PCBL -CC-PMA (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.
Figure 13: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-CC
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 14: Groundwater Level Representative Monitoring Network Wells with MT Exceedances in the PCBL-CC-PMA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 15: Groundwater Level Hydrograph for Well 01S09E05H002
Figure 16: Groundwater Level Hydrograph for Well #3 Bear Creek
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 17: Groundwater Level Hydrograph for Well Hirschfeld (OID8)
Under the PCBL with climate change but without Category A projects (PCBL-CC), all five representative monitoring network wells (Well 01S09E05H002, Well Swenson-3, Well #3 Bear Creek, Well Hirschfeld (OID8), and Well 01S10E04C001) exceed their MTs.
• Well 01S09E05H002:
o Exceeds its MT in 151 months out of a total of 624 months (24% of all months) and 17 water years out of a total of 52 water years (33% of all water years). o The exceedances occur in October of Year 22 after 3 consecutive drought years with exceedances continuing for 10 consecutive water years in total, and in October of Year 46 after 2 consecutive dry years with exceedances continuing for the remainder of the simulation or 7 consecutive water years in total.
• Well Swenson-3:
o Exceeds its MT in 65 months out of a total of 624 months (10% of all months) and 10 water years out of a total of 52 water years (19% of all water years). o The exceedances occur in July of Year 9 after 1 drought year with exceedances continuing for 2 consecutive water years in total, in October of Year 21 after 2 consecutive drought years with exceedances continuing for 5 consecutive water years in total, and in May of Ye ar 47 after 1 drought year with exceedances continuing for 3 consecutive water years in total. • Well #3 Bear Creek:
o Exceeds its MT in 52 months out of a total of 624 months (8% of all months) and 29 water years out of a total of 52 water years (56% of all water years). o The exceedances occur in October of Year 22 after 3 consecutive drought years with exceedances continuing for 17 consecutive water years in total, in October of Year 40 after a dry year with exceedances continuing for 4 consecutive water years in total, and in October of
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Year 45 after a dry year with exceedances continuing for the remainder of the simulation or 8 consecutive water years in total.
• Well Hirschfeld (OID8):
o Exceeds its MT in 113 months out of a total of 624 months (18% of all months) and 13 water years out of a total of 52 water years (25% of all water years). o The exceedances occur in August of Year 22 after 3 consecutive drought years with exceedances continuing for 8 consecutive wate r years in total, and in September of Year 46 after 2 consecutive dry years with exceedances continuing for 5 consecutive water years in total. • Well 01S10E04C001:
o Exceeds its MT in 512 months out of a total of 624 months (82% of all months) and 47 water years out of a total of 52 water years (90% of all water years). o The exceedances occur in July of Year 6 after a normal year with exceedances continuing for the remainder of the simulation or 47 consecutive water years in total.
Under the PCBL with climate change and w ith Category A projects (PCBL-CC-PMA), three representative monitoring network wells (Well 01S09E05H002, Well Hirschfeld (OID8), and Well 01S10E04C001) exceed their MTs.
• Well 01S09E05H002:
o Exceeds its MT in 4 months out of a total of 624 months (1% of all months) and 2 water years out of a total of 52 water years (4% of all water years). o The exceedances occur in September of Year 24 after 5 consecutive drought years with exceedances continuing for 2 consecutive water years in total. • Well Hirschfeld (OID8):
o Exceeds its MT in 7 months out of a total of 624 months (1% of all months) and 2 water years out of a total of 52 water years (4% of all water years). o The exceedances occur in September of Year 24 after 5 consecutive drought years with exceedances continuing for 2 consecutive water years in total. • Well 01S10E04C001:
o Exceeds its MT in 375 months out of a total of 624 months (60% of all months) and 41 water years out of a total of 52 water years (79% of all water years). o The exceedances occur in July of Year 8 in a drought year with exceedances continuing for 8 consecutive water years in total, and in July of Year 20 after a drought year with exceedances continuing for the remainder of the simulation or 33 consecutive water years in total.
Similar to what was seen with the PCBL and PCBL-PMA and as discussed in Section 3.2.2, Category A projects raise groundwater levels in varying amounts across the Subbasin. As seen with the five wells with MT exceedances in the PCBL -CC, the effects of climate change may continue to significantly impact Subbasin groundwater overdra ft and groundwater levels in the future . In the PCBL water budget scenario with projects and climate change factored in (PCBL-CC-PMA), modeling results show three wells still falling below their MTs for groundwater levels in the 52-year projection. All three of these wells are clustered in the same area of the Subbasin, perhaps indicating the need for additional study or a targeted project or management action specific to this area. The two wells that exceeded their MTs under PCBL-CC, but no longer exceeded under PCBL-CC-PMA were located in the areas with Category A projects.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.3.3 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 18 shows the number of wells with 2 consecutive water years of exceedances in the PCBL, PCBL-CC, PCBL-PMA and PCBL-CC-PMA models over 51 years of the simulation (since Year 1 cannot have 2 conse cutive years of exceedances) . Table 6 shows the number of water years out of the total possible 51 years with 2 consecutive years of exceedances in the same four simulations. All of the simulations have consecutive water years with MT exceedances occurring in at least one well. Only the PCBL-CC model is considered to have an undesirable result with five simulation years (Year 23, 24, 25, 48, and 49) with five representative monitoring network wells exceeding their MTs. These five years are all during or immediately following extreme drought conditions. No undesirable results were triggered in the PCBL, PCBL-PMA, and PCBL-CC-PMA models.
Figure 18: Number of Wells with 2 Consecutive Water Years of Exceedances
Table 6: 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 2.0) PCBL-PMA PCBL-CC PCBL-CC-PMA
1 Well 34 7 18 38
2 Wells 5 0 13 0
3 Wells 0 0 4 1
4 Wells 0 0 6 0
5 Wells 0 0 5 0
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
4. References
Woodard & Curran. 2022. Eastern San Joaquin Water Resources Model (ESJWRM) Version 2.0 Update.
Prepared for Eastern San Joaquin Groundwater Authority.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
APPENDIX A: NSJWCD PROJECT NUMBERS PROVIDED BY JENNIFER SPALETTA ON APRIL 21, 2022
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
APPENDIX B: ADDITIONAL PROJECTS PROPOSED AS CATEGORY A
The following projects were initially proposed as Category A projects, but were removed due to a lack of additional information provided. The information below is the project understanding as was understood at the time.
City of Stockton Morada Detention Basin
Submitting GSA: City of Stockton and Woodbridge Irrigation District (WID) Project Source : Project not included in GSP. Added based on information provided by personal communication with Mel Lytle (City of Stockton), Eric Houston (City of Stockton), and Mitchell Maidrand (City of Stockton) on April 21, 2022.
Project Type: Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing water right held by WID under both pre-1914 and post-1914 appropriative rights. Stormwater may also be utilized for recharge purposes.
Delivery Area: Morada Detention Basin (approximately 14.2 acres) Project Overview: This project is part of an agreement between City of Stockton and Woodbridge Irrigation District in September 2017 to use three storm bas ins in the northern part of City of Stockton for groundwater recharge of WID water. WID plans to use its pre -1914 unappropriated flows from the Mokelumne River and routed through WID’s South Canal and the Davis -Dolan Lateral. These flows could be supplemented with recovered stormwater during the winter months. One basin, the Morada Detention Basin, previously had groundwater recharge operations occur over the seven years from 2003 through 2009 with previous studies conducted by USGS indicating a positive re sponse in groundwater levels due to recharge operations. WID plans to utilize two additional basins (Cannery Park Northwest and Northeast Basins) where Mokelumne River flows or flood release water will be applied for groundwater recharge. The original contract between City of Stockton and WID for the use of the storm basins expires on June 30, 2027 and will need to be extended.
Project Volume:
No information on the availability of WID’s excess Mokelumne River water has been provided. Until more information becomes available, no water is assumed to be recharged in this project.
Baseline Water
Year Type
Annual Volume
(acre-feet per
year or AFY)
Notes
Drought 0
Dry 0
Normal 0
Wet 0
Woodbridge Irrigation District Cannery Park Regulating Basins Submitting GSA: City of Stockton and Woodbridge Irrigation District (WID)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Project Source : Project not included in GSP. Added based on information provided by personal communication with Mel Lytle (City of Stockton), Eric Houston (City of Stockton), and Mit chell Maidrand (City of Stockton) on April 21, 2022.
Project Type: Direct Recharge
Water Source: This project relies on water from the Mokelumne River. This is an existing water right held by WID under both pre-1914 and post-1914 appropriative rights. Stormwater may also be utilized for recharge purposes.
Delivery Area: Cannery Park Northeast and Northwest Basins (approximately 15 acres) Project Overview: This project is part of an agreement between City of Stockton and Woodbridge Irrigation District in September 2017 to use three storm basins in the northern part of City of Stockton for groundwater r echarge of WID water. WID plans to use its pre -1914 unappropriated flows off the Mokelumne River and routed through WID’s South Canal and the Davis -Dolan Lateral. These flows could be supplemented with recovered stormwater during the winter months. One bas in, the Morada Detention Basin, previously had groundwater recharge operations occur over the seven years from 2003 through 2009 with previous studies conducted by USGS indicating a positive response in groundwater levels due to recharge operations. WID plans to utilize two additional basins (Cannery Park Northwest and Northeast Basins) where Mokelumne River flows or flood release water will be applied for groundwater recharge. The original contract between City of Stockton and WID for the use of the storm basins expires on June 30, 2027 and will need to be extended.
Project Volume:
No information on the availability of WID’s excess Mokelumne River water has been provided. Until more information becomes available, no water is assumed to be recharged in this project.
Baseline Water
Year Type
Annual Volume
(acre-feet per
year or AFY)
Notes
Drought 0
Dry 0
Normal 0
Wet 0
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
APPENDIX C: GROUNDWATER LEVEL HYDROGRAPHS
Figure C-1: Groundwater Level Representative Monitoring Well Locations
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-2: Groundwater Level Hydrograph for Well 01S09E05H002
Figure C-3: Groundwater Level Hydrograph for Well 01N07E14J002
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-4: Groundwater Level Hydrograph for Well Swenson-3
Figure C-5: Groundwater Level Hydrograph for Well 02N08E15M002
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-6: Groundwater Level Hydrograph for Well #3 Bear Creek
Figure C-7: Groundwater Level Hydrograph for Lodi City Well #2
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-8: Groundwater Level Hydrograph for Well 18
Figure C-9: Groundwater Level Hydrograph for Well 04N07E20H003M
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-10: Groundwater Level Hydrograph for Well 03N07E21L003
Figure C-11: Groundwater Level Hydrograph for Well Hirschfeld (OID8)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-12: Groundwater Level Hydrograph for Well Burnett (OID4)
Figure C-13: Groundwater Level Hydrograph for Well 02S07E31N001
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-14: Groundwater Level Hydrograph for Well 02S08E08A001
Figure C-15: Groundwater Level Hydrograph for Well 02N07E03D001
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-16: Groundwater Level Hydrograph for Well 01N09E05J001
Figure C-17: Groundwater Level Hydrograph for Well 02N07E29B001
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-18: Groundwater Level Hydrograph for Well 04N05E36H003
Figure C-19: Groundwater Level Hydrograph for Well 03N06E05N003
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-20: Groundwater Level Hydrograph for Well 04N05E24J004
Figure C-21: Groundwater Level Hydrograph for Well 01S10E26J001M
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure C-22: Groundwater Level Hydrograph for Well 01S10E04C001
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ATTACHMENT 3 – ESJWRM Version 2.0 Update
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin
Water Resources Model
(ESJWRM)
Version 2.0 Update
Prepared for:
Eastern San Joaquin Groundwater Authority
UPDATED DRAFT
June 2, 2022
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table of Contents
SECTION PAGE NO.
1 HISTORICAL CALIBRATION UPDATE ................................ ................................ ............................... 1
1.1 Model Code and Data Updates Since the Groundwater Sustainability Plan ............................... 1
1.1.1 IWFM Version ........................................................................................................................................... 3
1.1.2 Updated Data from the ESJWRM version used in the Stanislaus River Basin Plan ...... 3
1.1.3 Hydrologic Period................................................................................................................................... 3
1.1.4 Precipitation .............................................................................................................................................. 3
1.1.5 Land Use and Cropping Patterns ..................................................................................................... 4
1.1.6 Stream Inflow ........................................................................................................................................... 6
1.1.7 Boundary Conditions............................................................................................................................. 7
1.1.8 Urban Demand ........................................................................................................................................ 7
1.1.9 Surface Water Diversions .................................................................................................................... 8
1.1.10 Groundwater Pumping .......................................................................................................................19
1.1.11 Agricultural Operations ......................................................................................................................19
1.2 Calibration Updates and Results .................................................................................................................20
1.2.1 Calibration Process...............................................................................................................................20
1.2.1.1 Agricultural Demand Calibration ...................................................................................21
1.2.1.2 PEST-Assisted Aquifer Calibration .................................................................................21
1.2.2 Calibration Verification .......................................................................................................................21
1.2.2.1 Streamflow Calibration ......................................................................................................21
1.2.2.2 Groundwater Level Calibration .......................................................................................24
1.2.3 Sensitivity Analysis ...............................................................................................................................26
1.3 Historical Model Results .................................................................................................................................30
1.3.1 Land and Water Use Budget ............................................................................................................30
1.3.2 Hydrologic Groundwater Budget ...................................................................................................33 2 PROJECTED CONDITIONS BASELINE UPDATE ................................ ................................ .............. 35
2.1 Assumptions Used to Develop Projected Conditions Baseline Update ......................................35
2.1.1 Hydrology ................................................................................................................................................35
2.1.1.1 Precipitation and Hydrologic Water Year Types ......................................................35
2.1.1.2 Evapotranspiration ..............................................................................................................38
2.1.1.3 Streamflow ..............................................................................................................................38
2.1.2 Land Use and Cropping Patterns ...................................................................................................38
2.1.3 Water Supply and Demand ..............................................................................................................40
2.2 Projected Conditions Baseline Results ......................................................................................................41
2.2.1 Land and Water Use Water Budget ...............................................................................................41
2.2.2 Hydrologic Groundwater Budget ...................................................................................................44 3 PROJECTED CONDITIONS BASELINE UPDATE WITH CLIMATE CHANGE ................................ ... 46
3.1 Climate Change Background and Methods ...........................................................................................46
3.1.1 DWR Guidance .......................................................................................................................................46
3.1.2 Climate Change Methodology ........................................................................................................49
3.2 Projected Conditions Baseline with Climate Change Hydrology ...................................................49
3.2.1 Streamflow under Climate Change ...............................................................................................50
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.2.1.1 Unimpaired Flows ................................................................................................................51
3.2.1.2 Impaired Flows ......................................................................................................................54
3.2.2 Precipitation and Evapotranspiration under Climate Change ............................................60
3.2.2.1 Applying Change Factors to Precipitation .................................................................60
3.2.2.2 Applying Change Factors to Evapotranspiration .....................................................63
3.3 Projected Conditions Baseline with Climate Change Results ..........................................................66
3.3.1 Differences in Precipitation, Evapotranspiration, and Streamflow under Climate Change ......................................................................................................................................................66
3.3.2 Land and Water Use Budget ............................................................................................................68
3.3.3 Groundwater Budget ...........................................................................................................................71 4 CONCLUSIONS AND RECOMMENDATIONS ................................ ................................ .................. 74 5 REFERENCES ................................ ................................ ................................ ................................ ..... 75
Tables
Table 1: Summary of ESJWRM Stream Inflow Data
Table 2: Summary of ESJWRM Surface Water Deliveries
Table 3: Summary of ESJWRM Well Pumping
Table 4: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Averages Table 5: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Averages Table 6: Baseline Hydrologic Water Year Types
Table 7: ESJ Subbasin Land Use Acreages by Land Use Type Table 8: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Table 9: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Table 10: DWR-Provided Datasets
Table 11: Eastern San Joaquin Stream Inflows
Table 12: San Joaquin Valley Water Year Type Designations Table 13: Comparable Water Years (based on Precipitation) Table 14: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average for PCBL -CC Table 15: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Comparison Between the PCBL and the PCBL-CC
Table 16: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Table 17: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL and the PCBL-CC
Figures
Figure 1: 2016 Land Use
Figure 2: 2016 Cropping Pattern for ESJ Subbasin
Figure 3: Streamflow Calibration
Figure 4: Groundwater Level Calibration
Figure 5: Calibration Statistics
Figure 6: Sensitivity of Groundwater Level Residual Statistics in Entire ESJWRM Figure 7: Sensitivity of Change in Groundwater Storage in ESJ Subbasin Figure 8: Sensitivity of Deep Percolation in ESJ Subbasin
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 9: Eastern San Joaquin Subbasin Agricultural Demand Figure 10: Eastern San Joaquin Subbasin Urban Demand
Figure 11: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Figure 12: Historical Precipitation in Eastern San Joaquin Subbasin Figure 13: 2018 Land Use with Urban Sphere of Influence Boundaries Figure 14: 2018 Cropping Pattern for ESJ Subbasin
Figure 15: Eastern San Joaquin Subbasin Projected Agricultural Demand Figure 16: Eastern San Joaquin Subbasin Projected Urban Demand Figure 17: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget Figure 18: Eastern San Joaquin Climate Change Analysis Process Figure 19: Dry Creek Hydrograph
Figure 20: Dry Creek Exceedance Curve
Figure 21: Mokelumne River Hydrograph
Figure 22: Mokelumne River Exceedance Curve
Figure 23: Calaveras River Hydrograph
Figure 24: Calaveras River Exceedance Curve
Figure 25: Stanislaus River Hydrograph
Figure 26: Stanislaus River Exceedance Curve
Figure 27: San Joaquin River Hydrograph
Figure 28: San Joaquin River Exceedance Curve
Figure 29: Tuolumne River Hydrograph
Figure 30: Tuolumne River Exceedance Curve
Figure 31: Cosumnes River Hydrograph
Figure 32: Cosumnes River Exceedance Curve
Figure 33: Perturbed Precipitation Under Climate Change Figure 34: Perturbed Precipitation Exceedance Curve
Figure 35: Subbasin Precipitation Difference with Climate Change Conditions Figure 36: Monthly Evapotranspiration Variability for Almonds Figure 37: Monthly Evapotranspiration Variability for Walnuts Figure 38: Monthly Evapotranspiration Variability for Cherries Figure 40: Simulated Changes in Precipitation due to Climate Change Figure 41: Simulated Changes in Evapotranspiration due to Climate Change Figure 42: Simulated Changes in Groundwater Pumping due to Climate Change Figure 43: Eastern San Joaquin Subbasin Projected Agricultural Demand in the PCBL -CC Figure 44: Eastern San Joaquin Subbasin Projected Urban Demand in the PCBL-CC Figure 45: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget
Appendices
Appendix A: ESJWRM Version 2.0 Land and Water Use Budgets for each GSA Appendix B: PCBL Version 2.0 Land and Water Use Budgets for each GSA
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
1 Historical Calibration Update
The Eastern San Joaquin Water Resources Model (ESJWRM) was developed primarily to evaluate the current and recent historical groundwater conditions of the Eastern San Joaquin Groundwater Subbasin (ESJ Subbasin or Subbasin ) and simulate various current and future condition scenarios as part of the Groundwater Sustainability Plan (GSP) pr eparation process under the Sustainable Groundwater Management Act (SGMA) (Woodard & Curran, 2018a). The fine geographic scale of the model provides the opportunity for individual Groundwater Sustainability Agencies (GSAs) to evaluate the effect of changin g ESJ Subbasin conditions on smaller GSA areas. The Eastern San Joaquin Groundwater Authority (ESJGWA) was formed by a Joint Powers Agreement (JPA) and coordinates the SGMA activities for the Subbasin. The ESJGWA members include the 16 GSAs in the Subbasin.
ESJWRM uses the Integrated Water Flow Model (IWFM-2015) platform, has a finite element grid, includes data on a monthly time step, and covers the area of Cosumnes Subbasin, Eastern San Joaquin Subbasin, Modesto Subbasin, and the portion of the City of Lathrop east of San Joaquin River in the Tracy Subbasin .
The original development of ESJWRM was from 2016 through 2018, with application of ESJWRM to GSP development occurring from 2018 through 2020 and resulting in a November 2019 GSP (ESJGWA, 2019) .
The GSP version of the ESJWRM (ESJWRM Version 1.1), which covers Water Years (WY) 1995 through 2015 (October 1994 through September 30, 2015), was documented in an August 2018 report (Woodard & Curran, 2018a) as well as a February 2018 technical memorandum (Wo odard & Curran, 2018b). The earlier reports cover the development of the model, the model platform, the model framework, and all input data and results. This report serves as an update to the earlier model report (Woodard & Curran, 2018a) and only discusses portions of the model that were updated as part of the recent effort to develop ESJWRM Version 2.0, as well as a complete discussion of updated model results. This section includes all the updates made to ESJWRM Version 2.0.
1.1 Model Code and Data Updates Since the Groundwater Sustainability Plan Since the ESJ Subbasin GSP was finalized in November 2019, the ESJWRM has undergone three updates:
1. Extension of Data from Water Year 2016 through Water Year 2019
2. Extension of Data through Water Year 2020
3. Full Model Update and Recalibration (resulting in ESJWRM Version 2.0) The first two updates were completed as part of the preparation of ESJ Subbasin GSP annual reports to the Department of Water Resources ( DWR). These updates only included an extension of mode l time series data (i.e., land use, surface water diversions, groundwater well pumping, and urban demand) and the model provided estimates of total surface water supplies, groundwater pumping, and change in groundwater storage for the water year covered by the model report. The third and major update is the focus of this report and the majority of the work was performed in 2021. Through discussions with GSAs near the completion of the GSP, several areas for update and re finement in the ESJWRM were identified . The goals of the 2021 model update to ESJWRM Version 2.0 were to:
1. Confirm the data in the ESJWRM is the latest hydrologic , water supply , and operations data available. This includes updating issues identified through discussions with the GSAs as part of the GSP process and including newer data and techniques that were unavailable in the development of the original model.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
2. Refine the model calibration to ensure a reasonable representation of the hydrologic conditions in the ESJ Subbasin with the updated data and observation information.
3. Update the projected conditions baseline to estimate conditions in the ESJ Subbasin at buildout (approximately 2040) without GSP projects and potential climate change conditions. This update is discussed in Section 2.
4. Use the updated ESJWRM versions to develop water budgets at the GSA level to understand the water operations for each GSA to support a water accounting framework and assessment of benefits and impacts of sustainability actions at the GSA level . This is discussed in Section Error! Reference source not found..
The data update was completed through extensive outreach to GSAs and Subbasin agencies and coordination with the ESJGWA Technical Advisory Committee (TAC) , including meeting pre sentations and interaction with stakeholders. Data for the model update included a variety of agencies and GSAs. Below is a list of the agencies that provided data and input on the model update:
Agricultural Water Purveyors
• Calaveras County Water District (CCWD)
• Central San Joaquin Water Conservation District (CSJWCD) • North San Joaquin Water Conservation District (NSJWCD) • Oakdale Irrigation District (OID)
• South San Joaquin Irrigation District (SSJID)
• Stockton East Water District (SEWD)
• Woodbridge Irrigation District (WID)
Municipal Water Purveyors
• California Water Service Company Stockton District (Cal Water) • City of Escalon
• City of Lodi
• City of Manteca
• City of Ripon
• City of Stockton
• Linden County Water District (LCWD)
• Lockeford Community Services District (LCSD)
• Stockton East Water District (SEWD)
For the update to ESJWRM Version 2.0, more extensive coordination was appreciated from the following people:
• Eric Houston (City of Stockton)
• Justin Hopkins (SEWD)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
• Mike Henry (LCSD)
• Dave Fletcher (LCWD)
• Alan Nakanishi and Travis Kahrs (City of Lodi)
• Jennifer Spaletta (NSJWCD)
• Eric Thorburn and Emily Sheldon (OID)
• Brandon Nakagawa (SSJID)
• Matt Zidar and Glenn Prasad (San Joaquin County)
1.1.1 IWFM Version
The model platform, IWFM-2015, has had several upd ates since ESJWRM Version 1.1 was originally developed and the IWFM code has been updated to the latest release version (IWFM -2105 Version 1273) for ESJWRM Version 2.0. New IWFM versions typically include error fixes and larger code changes that may impact the underlying calculations and therefore model results . Changes between model versions are documented on DWR’s IWFM website ( https://water.ca.gov/Library/Modeling-and-Analysis/Modeling- Platforms/Integrated-Water-Flow-Model) and the latest IWFM technical memorandums are available online (Dogrul and Kadir, 2021a and 2021b).
1.1.2 Updated Data from the ESJWRM version used in the Stanislaus River Basin Plan A modified version of ESJWRM Version 1.1 was prepared as part of the Stanislaus River Basin Plan . The Stanislaus River Basin Plan, a collaborative effort by Oakdale Irrigation District (OID) and South San Joaquin Irrigation District (SSJID), is still in draft format and is discussed in the respective agricultural water management plans (AWMP) (OID, 2 021) (SSJID, 2021) . The changes made to the modified version of ESJWRM Version 1.1 were incorporated into the 2021 update to ESJWRM Version 2.0. The changes were focused on Modesto Subbasin and OID, both in ESJ Subbasin and in Modesto Subbasin. Changes included updating agricultural and urban pumping in Modesto Subbasin, surface water diversion and groundwater pumping time series, surface water diversion and groundwater pumping delivery areas for OID and Modesto Subbasin agencies, target soil moisture percentage, agricultural return flow fraction, and Modesto Reservoir seepage. Changes to the Modesto Subbasin are not discussed in detail in the sections below.
1.1.3 Hydrologic Period
The updated ESJWRM Version 2.0 simulates water years 1995 through 2 020 (October 1, 1994 through September 30, 2020). It was extended five water years from ESJWRM Version 1.1. Due to the extension of the period covered by the model, all model data with monthly or annual values had to be extended. These updates are listed in the sections below.
1.1.4 Precipitation
As with ESJWRM Version 1.1, rainfall data for the model area is derived from the PRISM (Precipitation - Elevation Regressions on Independent Slopes Model) database used in the DWR’s CALSIMETAW (California Simulation of Evapotranspiration of Applied Water) model. The database contains daily precipitation data from October 1, 1921 on a 4-kilometer grid throughout the model area (OSU, 2021). ESJWRM has monthly rainfall data defined for every model element and adjacent foothill watershed in order to preserve the spatial distribution of the monthly rainfall. Each of the model elements was mapped to the nearest of 364 available
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
PRISM reference nodes, uniformly distributed across the model domai n. ESJWRM Version 2.0 includes the mapped precipitation time series for water years 2016 through 2020.
1.1.5 Land Use and Cropping Patterns
ESJWRM Version 2.0 utilizes the same land use categories as ESJWRM Version 1.1 as documented in the earlier reports (Woodard & Curran, 2018a and 2018b). The data through water year 2015 is the same as ESJWRM Version 1.1, except for minor tweaks to land use around the Subbasin’s two smallest GSAs, Lockeford Community Services District (LCSD) and Linden County Water Distr ict (LCWD). Due to the small size of these GSAs, model elements did not exactly align wi th GSA boundaries, so agricultural land use associated with the surrounding districts, North San Joaquin Water Conservation District (NSJWCD) for LCSD and Stockton East Water District (SEWD) for LCWD, was included in elements representing these two small urban communities. In discussions with the GSAs, it was agreed that the agricultural land use would be removed from model elements assigned to LCSD (15 elements) and LCWD (5 elements). In total, this edit impacted an average of 250 acres per year.
DWR released a statewide crop mapping for 2016 that was completed using remote sensing methods to collect and process the data at the parcel scale and was then ground truthed for a high overall accuracy (DWR, 2016). This spatial land use data was mapped to ESJWRM model elements and assumed to represent land use for all extended water years (2016 through 2020). Based on discussions with SSJID and comparison with the most recent AWMP (SSJID, 2021), the 2016 land use for SSJID was replaced with the data for 2015 from ESJWRM Version 1.1.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 1: 2016 Land Use
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 2: 2016 Cropping Pattern for ESJ Subbasin
1.1.6 Stream Inflow
Stream inflows to the model were extended using updated data from United States Geological Survey (USGS) stream gages and the United States Army Corps of Engineers (USACE) reservoir releases. Dry Creek, with data estimated using a regression after January 1998, was updated using recent monthly averages for similar water year types. A column was added for SSJID system outflows to Stanislaus River, discussed further in Section 1.1.11 below. A table of stream input data may be found in Table 1.
Table 1: Summary of ESJWRM Stream Inflow Data
Stream Stream
Node Source Gage Name Period of Record
Average
Annual
Streamflow
(acre-feet)
Cosumnes
River 1 USGS
USGS 11335000:
Cosumnes River at
Michigan Bar, CA
October 1907 to
present/ongoing 397,000
Dry Creek 140
USGS
Estimated in C2VSim by
correlation with USGS
11329500: Dry Creek near
Galt, CA
Not continuous
October 1926 to
December 1997
29,000
USGS
Estimated in C2VSim by
correlation with USGS
11335000: Cosumnes River
at Michigan Bar, CA
Used October 1987
to September 1995
and January 1998
to September 2015
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Stream Stream
Node Source Gage Name Period of Record
Average
Annual
Streamflow
(acre-feet)
n/a
Average of Historical Data
by Month and Water Year
Type
Used October 2015
to present/ongoing
Mokelumne
River 290 USGS
USGS 11323500:
Mokelumne River below
Camanche Dam, CA
October 1904 to
present/ongoing 562,000
Calaveras River 758
USGS
USGS 11308900: Calaveras
River below New Hogan
Dam near Valley Springs,
CA
February 1961 to
September 1990 160,000
USACE New Hogan Dam releases October 1990 to
present/ongoing
Stanislaus River 1033 USGS
USGS 11302000: Stanislaus
River below Goodwin Dam
near Knights Ferry, CA
February 1957 to
present/ongoing 576,000
Tuolumne River 1248 USGS
USGS 11289650: Tuolumne
River below Lagrange Dam
near Lagrange, CA
October 1970 to
present/ongoing 905,000
San Joaquin
River 1497 USGS
USGS 11303500: San
Joaquin River near
Vernalis, CA
October 1923 to
present/ongoing 3,162,000
SSJID System
Outflows to
Stanislaus River
1212 SSJID n/a n/a 24,000
1.1.7 Boundary Conditions
The boundary conditions in the model remain the same as ESJWRM Version 1.1, with eastern flows from the Sierra Nevada Mountains simulated in the model as small watersheds, Camanche Reservoir seepage estimated using a constrained general head boundary condition, Woodward Reservoir and Modesto Reservoir seepage represented as stream diversions, flows from outside of the model area represented with general head boundary conditions , and groundwater levels at or near zero near the edges of the Sacramento-San Joaquin Delta are represented using specified head boundary conditions.
Data was extended through water year 2020 using a monthly average by water year type. Data for water years 2010 through 2015 were recalculated and updated in the model . The heads near the Delta were adjusted based on analysis of nearby observed groundwater levels.
1.1.8 Urban Demand
Urban demand, comprised of annual population and monthly per capita water use (PCWU), is specified for incorporated urban areas or communities and estimated for rural urban demand. Changes to ESJWRM Version 1.1 were to add specified urban areas for Jenny Lind (in Calaveras County with a portion of the city
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
outside of ESJ Subbasin) and in Modesto Subbasin (Oakdale, Riverbank, Waterford, and Modesto). City of Stockton, which was previously separated into portions for City of Stockton and California Water Service Company Stockton District (Cal Water) , was updat ed to separate out the areas of unincorporated San Joaquin County land from City of Stockton . All urban areas were reviewed and updated to match areas where urban surface water deliveries and urban groundwater pumping was supplied. Urban surface water supply is assumed to have both indoor and outdoor usage, of which excess outdoor use returns to the model streams or percolates into the groundwater system.
Updated population for w ater years 2016 through 2020 using data from the California Department of Finance (DOF, 2021) . The population for the entire Stockton area was updated for the entire model simulation period to data from the California Department of Finance . Based on review by LCSD, LCSD population for the entire model simulation period was updated using historical population and population projections in the 2016 LCSD Municipal Services Review (LCSD, 2016). The rural population, or people not in incorporated areas, was estimated by calculating an estimate of the rural population per acre in San Joaquin County and applying that population estimate to the unincorporated acreage of the model.
Urban demand was calculated for each area as the sum of the surface water (if the agency received surface water) and the groundwater pumping . The updated water supply is discussed in the sections below for surface water (Section 1.1.9) and groundwater (Section 1.1.1). The PCWU was then calculated for each agency as the monthly calculated demand divided by the annual population. Calculating the PCWU directly from the supplied water mitigates issues with urban surplus or shortage in the land and water use budget.
1.1.9 Surface Water Diversions
Surface water diversions were fully reorganized and renumbered in ESJWRM Version 2.0 and many additional diversions were included that were not in ESJWRM Version 1.1. Diversion edits included splitting NSJWCD’s agricultural diversion from Mokelumne River into two time series for the NSJWCD north and south service areas ; including NSJWCD r echarge projects; refinement of NSJWCD recharge and irrigation schedules; adjustments to Lodi’s data; adding the urban delivery of Calaveras River water from Calaveras County Water District (CCWD) to Jenny Lind (assuming 43% of Jenny Lind lies within ESJ Subbasin); updating OID north and south and SSJID deliveries to better represent what the AWMPs report for farm deliveries, recycled water deliveries, annual contract deliveries , and canal and drain seepage ; separating urban deliveries to City of Stockton area into separate time series for City of Stockton, Cal Water, and San Joaquin County users in City of Stockton ; separating SEWD diversion losses from Calaveras and Stanislaus Rivers into separate time series; additional diversions to Modesto Subbasin included as part of model refinements for the Stanislaus River Basin Plan; and the update of surface water delivery estimates for areas of the Delta and riparian user areas along the rivers.
All GSAs were provided all model historical supply data to review and updat e during the development of ESJWRM Version 2.0. Additionally, all surface water diversion delivery groups were reviewed and updated to reflect a more recent understanding of Subbasin surface water operations. A summary of diversions simulated in the model is provided in Table 2, along with fractions for recoverable loss (i.e., percolation or canal seepage), non-recoverable loss (i.e., evaporation), and delivery (i.e., amount delivered is equal to the total amount minus the recoverable and non -recoverable losses). ESJWRM Version 2.0 includes 66 diversions, 61 of which are listed in Table 2 and 5 diversions that are placeholders that are not currently being used in the model. The Projected Conditions Baseline Version 2.0 averages are also included in Table 2 and are discussed in Section 2.1.3.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 2: Summary of ESJWRM Surface Water Deliveries
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
1 Mokelumne River to
North San Joaquin
WCD North System
for Ag
Mokelumne
River
North San
Joaquin WCD
North System
Ag 50% 0% 50% 360 0 NSJWCD
2 Mokelumne River to
North San Joaquin
WCD South System
for Ag
Mokelumne
River
North San
Joaquin WCD
South System
Ag 50% 0% 50% 1,900 2,000 NSJWCD
3 Mokelumne River to
North San Joaquin
WCD for CALFED GW
Recharge Project
Mokelumne
River
CALFED GW
Recharge Project Recharge 100% 0% 0% 260 800 NSJWCD
4 Mokelumne River to
North San Joaquin
WCD For Tracy Lake
Recharge Project
Mokelumne
River
Tracy Lake
Recharge Project Recharge 50% 0% 50% 320 3,200 NSJWCD
5 Mokelumne River to
City of Lodi (by
agreement with
Woodbridge ID) for
M&I
Mokelumne
River City of Lodi Urban 0% 0% 100% 5,500 4,700 Lodi
6 Mokelumne River to
City of Lodi (by
agreement with
NSJWCD) for M&I
Mokelumne
River City of Lodi Urban 0% 0% 100% 370 0 Lodi
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
7 Mokelumne River to
City of Lodi (banked
from agreement with
WID) for M&I
Mokelumne
River City of Lodi Urban 0% 0% 100% 560 0 Lodi
8 Mokelumne River to
Woodbridge ID for
Ag
Mokelumne
River
Woodbridge
Irrigation District Ag 30% 2% 68% 58,800 44,200 WID
9 Mokelumne River
Export to Contra
Costa WD (by
agreement with
Woodbridge ID)
Mokelumne
River
Export out of
model Urban 0% 0% 100% 2,000 (one
year only) 0 WID
10 Mokelumne River to
City of Stockton for
Delta Water Supply
Project (by
agreement with
Woodbridge ID) for
M&I
Mokelumne
River City of Stockton Urban 0% 0% 100% 7,700 10,500 City of Stockton
11 San Joaquin River at
Empire Tract to City
of Stockton for Delta
Water Supply Project
for M&I
San Joaquin
River City of Stockton Urban 0% 0% 100% 8,500 21,600 City of Stockton
12 Calaveras River to
Bellota Pipeline to
Stockton East WD
WTP for M&I
Calaveras
River
Export out of
model (imported
in Diversions 14,
15, and 16)
Urban 0% 0% 100% 13,800 13,100 SEWD
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
13 Stanislaus River at
Goodwin Dam to
Farmington Flood
Control Basin to
Lower Farmington
Canal to Peters
Pipeline to Stockton
East WD WTP for
M&I
Import
(outside of
ESJWRM)
Export out of
model (imported
in Diversions 14,
15, and 16)
Urban 0% 0% 100% 29,400 49,900 SEWD
14 Stockton East WD
WTP to City of
Stockton for M&I
Import
(exported in
Diversions 12
and 13)
City of Stockton Urban 0% 0% 100% 18,800 5,100 UWMP
15 Stockton East WD
WTP to Cal Water for
M&I
Import
(exported in
Diversions 12
and 13)
Cal Water Urban 0% 0% 100% 21,800 19,300 UWMP
16 Stockton East WD
WTP to San Joaquin
County in Stockton
for M&I
Import
(exported in
Diversions 12
and 13)
San Joaquin
County in
Stockton
Urban 0% 0% 100% 1,400 1,500 UWMP
17 Calaveras River to
Calaveras County WD
for Ag
Import
(outside of
ESJWRM)
Calaveras County
WD Ag 9% 1% 90% 1,100 1,300 CCWD
18 Calaveras River to
Jenny Lind for M&I
Import
(outside of
ESJWRM)
Jenny Lind Urban 0% 0% 43% 1,800 1,800 CCWD
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
19 Calaveras River to
Stockton East WD for
Ag
Calaveras
River
Stockton East
Water District Ag 0% 0% 100% 23,600 21,100 SEWD
20 Calaveras River to
Stockton East WD
Losses
Calaveras
River
Stockton East
Water District,
including canals
Recharge 89% 11% 0% 19,300 15,200 SEWD
21 Calaveras River to
Farmington
Groundwater
Recharge Program
Calaveras
River
Farmington
Groundwater
Recharge
Program
Recharge 100% 0% 0% 1,400 5,200 SEWD
22 San Joaquin River to
North Delta for Ag
San Joaquin
River
North Delta
Subregion Ag 5% 1% 94% 139,600 125,800 Estimated
by model
23 San Joaquin River to
South Delta for Ag
San Joaquin
River
South Delta
Subregion Ag 5% 1% 94% 26,700 18,500 Estimated
by model
24 Stanislaus River at
Goodwin Dam to
Farmington Flood
Control Basin to
Lower Farmington
Canal to Stockton
East WD for Ag
Import
(outside of
ESJWRM)
Stockton East
Water District Ag 0% 0% 100% 4,400 6,800 SEWD
25 Stanislaus River to
Stockton East WD
Losses
Import
(outside of
ESJWRM)
Stockton East
Water District,
including canals
#N/A 88% 12% 0% 900 1,200 SEWD
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
26 Stanislaus River at
Goodwin Dam to
Farmington Flood
Control Basin via
Little Johns Creek and
Lower Farmington
Canal to Central San
Joaquin WCD for Ag
Import
(outside of
ESJWRM)
Central San
Joaquin WCD Ag 15% 2% 83% 30,000 24,300 SEWD
27 Stanislaus River to
Farmington
Groundwater
Recharge Program
Import
(outside of
ESJWRM)
Farmington
Groundwater
Recharge
Program
Recharge 100% 0% 0% 3,300 4,900 SEWD
28 Stanislaus River at
Goodwin Dam to
Oakdale ID North for
Ag
Import
(outside of
ESJWRM)
Export out of
model (imported
in Diversions 52,
55, and 57)
Ag 0% 0% 0% 98,800 88,000 OID
29 Stanislaus River at
Goodwin Dam to
Oakdale ID South for
Ag [Modesto
Subbasin]
Import
(outside of
ESJWRM)
Export out of
model (imported
in Diversions 53,
54, 56, and 58)
Ag 0% 0% 0% 136,400 121,500 OID
30 Stanislaus River to
Woodward Reservoir
to South San Joaquin
ID for Ag
Import
(outside of
ESJWRM)
Export out of
model (imported
in Diversions 59,
60, and 61)
Ag 0% 0% 0% 189,500 150,000 SSJID
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
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% 5,200 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% 6,800 10,700 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% 1,400 6,300 UWMP
36 Stanislaus River to
Woodward Reservoir
to Nick C. DeGroot
WTP to City of Ripon
for M&I
Import
(outside of
ESJWRM)
City of Ripon Urban 0% 0% 100% 0 0 UWMP
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
37 Tuolumne River to
Modesto ID for Ag
[Modesto Subbasin]
Import
(outside of
ESJWRM)
Modesto ID Ag 3% 19% 78% 232,500 196,000
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% 30,700 27,100
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% 2,800 2,300 C2VSim
40 Dry Creek to Riparian
for Ag [Split Across
Subbasins]
Dry Creek Riparian diverters
along river Ag 10% 2% 88% 5,600 6,400 C2VSim
41 Mokelumne River to
Riparian for Ag
Mokelumne
River
Riparian diverters
along river Ag 10% 2% 88% 9,600 11,300 C2VSim
42 Calaveras River to
Riparian for Ag
Calaveras
River
Riparian diverters
along river Ag 10% 2% 88% 11,400 10,900 C2VSim
43 Stanislaus River to
Riparian for Ag [Split
Across Subbasins]
Stanislaus
River
Riparian diverters
along river Ag 15% 3% 82% 30,600 30,400 C2VSim
44 Tuolumne River to
Riparian for Ag
[Modesto Subbasin]
Tuolumne
River
Riparian diverters
along river Ag 15% 3% 82% 6,100 6,300 C2VSim
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
45 San Joaquin River to
Riparian for Ag [Split
Across Subbasins]
San Joaquin
River
Riparian diverters
along river Ag 15% 3% 82% 5,800 5,900 C2VSim
46 Modesto ID
Groundwater
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of
ESJWRM)
Modesto ID Ag 0% 0% 100% 21,500 24,300
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% 33,100 32,200
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% 4,600 4,800
Stanislaus
River Basin
Plan
ESJWRM
Update
50 City of Waterford GW
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of
ESJWRM)
City of Waterford Urban 3% 1% 96% 1,700 1,500
Stanislaus
River Basin
Plan
ESJWRM
Update
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
51 City of Riverbank GW
Pumping Deliveries
[Modesto Subbasin]
Import
(outside of
ESJWRM)
City of Riverbank Urban 3% 1% 96% 4,500 4,400
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% 78,900 75,100 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% 121,000 114,400 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 3,300 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% 2,100 2,600 OID AWMP
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% 2,300 2,500 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 17,500 OID AWMP
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ID Description Diversion
Location Delivery Area Primary
Use
Fraction
ESJWRM
Version 2.0
Average
Annual
Diversion***
(acre-feet)
PCBL
Version 2.0
Average
Annual
Diversion***
(acre-feet)
Data
Source
RL* NL** Delivery
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% 18,300 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% 144,000 120,000 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 28,200 SSJID
AWMP
*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)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
1.1.10 Groundwater Pumping
Groundwater pumping within ESJWRM is separated into well - or element -based pumping. The former largely includes district -operated wells that feed into the surface water supply network, while the latter includes estimated private groundwater pumping.
Updates to ESJWRM Version 2.0 for well pumping was the addition of Modesto Subbasin wells included in the model updates made for the Stanislaus River Basin Plan and the addition of two OID wells. OID and SSJID district wells were updated to export water out of the model since the district groundwater pumping is included in the farm deliveries to SSJID, OID North, and OID South included as surface water deliveries.
Additionally, all groundwater pumping delivery groups were reviewed and updated to reflect a more recent understanding of Subbasin operations. Table 3 lists the number of wells by type and agency included in ESJWRM.
Element pumping is estimated by IWFM within the model simulation. Element pumping in ESJWRM Version
2.0 was updated to remove all model-calculated groundwater pumping for urban uses in urban areas.
Table 3: Summary of ESJWRM Well Pumping
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 56 --- 8,200 0
Escalon 4 --- 1,400 0
Lathrop 6 --- 2,200 0
Linden County WD 4 --- 440 0
Lockeford CSD 4 --- 510 0
Lodi 29 --- 13,600 0
Manteca 15 31 9,300 1,300
Oakdale ID* --- 26 0 6,700
Ripon 9 9 3,900 1,000
SEWD 5 --- 590** 0
SSJID --- 28 0 5,200
Stockton 37 --- 8,500 0
Other Modesto
Subbasin Wells --- 246 0 68,000
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 2015-2020)
1.1.11 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Both SSJID and OID report large amounts of tailwater as outflow from the district s’ drainage systems in their respective AWMPs (SSJID, 2021) (OID, 2021) . For OID, the amount of tailwater from the district lands is represented through adjustments to the return flow fraction , which controls how much of applied water ultimately ends up as drainage to model stream nodes . For SSJID, since the majority of the tailwater ends up back in Stanislaus River the reported system outflows are included as a stream inflow to Stanislaus River below SSJID. The return flow fraction was likewise adjusted for SSJID’s area.
The reuse fraction is the percent of applied water that can be reused as irrigation to meet demand. Based on analysis of the OID 2020 AWMP (OID, 2021), the reuse fraction for OID model elements was set to 2%.
The target soil moisture specifies the fraction of field capacity that IWFM will iterate to and was utilized to adjust OID demand, first in the adjusted version of ESJWRM Version 1.1 prepared for the Stanislaus River Basin Plan and then adjusted based on analysis of the OID 2020 AWMP (OID, 2021) .
Canal and drain seepage for the agricultural agencies is included in surface water diversion information and discussed in Section 1.1.9 above. For agencies that may have surface water agreements where a portion of the delivery losses is assumed to occur in the river (e.g., NSJWCD), the interaction between the stream and the groundwater system is simulated separately in ESJWRM and assumed to account for the conveyance losses. This is considered a special case in the operational water budget discussed in Section Error! Reference source not found..
All other files that control agricultural operations were extended through water year 2020 by repeating the recent historical data.
1.2 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 2020 or water years 1996 through 2020 (25 years).
1.2.1 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
• Perform sensitivity analysis
• Conduct additional refinements to model as necessary
1.2.1.1 Agricultural Demand Calibration
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 calibration serves as the foundation of the IWFM calibration for agricultural areas, as demand estimated often translates directly to groundwater pumping, which is the primary stress on the groundwater system. To adjust agri cultural demand, element -level root zone parameters, particularly the soil hydraulic conductivity, were adjusted in accordance with the hydrologic soil group and area of the model. Soil hydraulic conductivity was adjusted in the areas of the model representing OID North, NSJWCD, and SSJID to better match reported groundwater pumping, demand, and per unit water use.
During agricultural demand calibration, also called root zone calibration , the curve numbers assigned to different land uses were also reviewed. Based on review of percolation of precipitation occurring in different areas of the model, the curve numbers for native and riparian land uses were adjusted. Additionally, refinements were made to the unsaturated zone initial soil moisture to standardize the amount of water in the unsaturated zone from year to year.
1.2.1.2 PEST-Assisted Aquifer Calibration
Aquifer parameter calibration of ESJWRM utilized a parametric grid covering the model area that reflected the scale at which parameters were adjusted througho ut 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.
Due to the complexities of calibrating an integrated water resources model, a hybrid approach for calibration was utilized to perform a manual calibration on initial water budgets and regional groundwater conditions and a PEST -assisted calibration using PE ST (Doherty, 2015) to achieve a refinement of the calibrated parameters that would result in a more accurate simulation. The use of the PEST software package is discussed further in Section 1.2.2.2.
1.2.2 Calibration Verification
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 (mainly g athered during TAC meetings), agricultural water management plans , urban water management plans , other local planning efforts, measured groundwater levels, and observed streamflow data.
1.2.2.1 Streamflow Calibration
Streamflow calibration is primarily performed by comparing the simulated streamflow with local observation data for 11 stream gages located on major streams. Data for these gages came from USGS , USACE, or the California Data Exchange Center (CDEC). Two of these stream gages (Mokelumne River below Camanche
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Dam and San Joaquin River near Vernalis) are duplicates of gages used to estimate stream inflow into the model area and were not referenced for streamflow cal ibration and only included as verification of the model setup.
Streambed hydraulic conductivity was adjusted during model calibration based on examination of stream flow hydrographs and stream reach water budgets. The portion of Mokelumne River through Cam anche Reservoir (Reach 3) was assigned a streambed hydraulic conductivity of zero since all the surface water - groundwater interaction is already represented by the constrained general head boundary condition representing Camanche Reservoir. Additionally, s treambed hydraulic conductivities were examined in the overlapping models of DWR’s California Central Valley Groundwater -Surface Water Simulation Model with fine grid (C2VSimFG) and the Cosumnes -South American -North American Integrated Water Resources Model (CoSANA) and adjusted for some corresponding streams.
Simulated stream flows were compared with observed records and exceedance charts were also used to check the model performance when simulating high and low flows at each gage location. Calibration results for select stream gages are included in Figure 3.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 3: Streamflow Calibration
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
1.2.2.2 Groundwater Level Calibration
The goal of groundwater level calibration is to achieve the maximum agreement between simulated and observed groundwater elevations at calibration w ells while maintaining reasonable values for aquifer parameters. During the calibration of ESJWRM Version 1.1 , 70 wells were ultimately selected that were representative of the long -term conditions of groundwater levels both at a local and regional scale in ESJWRM. This same set of calibration points was kept for ESJWRM Version 2.0, with the addition of GSP Representative Monitoring Network wells if they were not already included.
Simulated groundwater levels are calibrated to observed levels through adjustments to hydrogeologic parameters or aquifer parameters including hydraulic conductivity, specific storage, and specific yield. The automated parameter es timation tool, PEST, was used to assist in refinement of aquifer parameters to improve model calibration. PEST -assisted calibration is performed to interact with ESJWRM via input and output files and iteratively modifies parameter values to reduce an objective function representative of the model residual error. These modifications are made within identified bounds of reasonable values for each parameter. PEST -assisted calibration focused on the aquifer parameters such as horizontal and vertical conductivities and storage parameters. Between PEST -assisted calibration iterations, the modeling team revisited the land system and small watershed budgets and made manual adjustments where needed, until calibration goals were met.
The results of the groundwater level calibration indicate that the ESJWRM reasonably simulates the long - term hydrologic responses u nder various hydrologic conditions. Figure 4 shows a selection of calibration wells with their resulting groundwater level hydrographs showing the updated calibration of ESJWRM Version 2.0. All ESJWRM Version 2.0 groundwater level hydrographs may be downloaded as a Google Earth KMZ file at (Link to be provided).
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 4: Groundwater Level Calibration
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 f or 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.
• 44% of observed groundwater levels are within +/- 5 feet of its respective simulated values • 73% of observed groundwater levels are within +/- 10 feet of its respective simulated values • 96% of observed groundwater levels are within +/- 20 feet of its respective simulated values The residual histogram and scatter plot of simulated versus observ ed values for the ESJ Subbasin original calibration wells for the calibration period is shown in Figure 5. The scatter plot colors points by input data subregion. The highest elevations are seen in model subregions closer to the foothills (e.g., Subregion 5 and 17).
Figure 5: Calibration Statistics
1.2.3 Sensitivity Analysis
Sensitivity analysis is a way of investigating h ow 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
that parameter within its valid range. Conversely, an insensitive parameter means the cha nges 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. For this reason, sensitivit y analysis is an important step of the model calibration process. The sensitivity analysis serves the following purposes:
• To improve the understanding of input-output relationships • To quantify the impact of inaccuracies in model parameters • To evaluate the stability and robustness of the model • To understand the overall range of accuracy of the model results For these purposes, the following set of calibration parameters were selected for investigation under ESJWRM sensitivity analysis:
• Aquifer horizontal hydraulic conductivity (Kh) changed globally by factors of 0.5, 0.67, 1.5, 2.0 • Aquifer vertical hydraulic conductivity (Kv) changed globally by factors of 0.5, 0.67, 1.5, 2.0 • Aquitard vertical hydraulic conductivity (Kaqt) changed globally by factors of 0.5, 0.67, 1.5, 2.0 • Specific yield (Sy) changed globally by factors of 0.8, 1.2 • Specific storage (Ss) changed globally by factors of 0.1, 0.2, 5, 10 • Streambed hydraulic conductivity (Kstr) changed globally by factors of 0.2, 0.5, 2.0, 5.0 • Boundary condition conductance for both general and constrained general head (BC_Cond) changed globally by factors of 0.5, 0.67, 1.5, 2.0
• Saturated soil hydraulic conductivity (Ksoil) changed globally by factors of 0.2, 0.5, 2.0, 5.0 • Target soil moisture (TSM) changed globally by setting all values to 0.6 or 0.8 In the process of evaluating the sensitivity of model resul ts to certain parameter changes, the results from the 32 sensitivity runs were analyzed for the ESJ Subbasin and model as a whole and compared to the calibrated model in terms of the groundwater residual statistics. As the changes to the input parameters for sensitivity analysis were made globally, the changes in the model performance were also considered on a global or subregional scale. An improvement in the model performance based on changes in one parameter at a global scale does not necessarily mean im provements in the overall model performance and/or calibration, as the model is calibrated to a number of target parameters, only some of which may be included in the performance assessment during the sensitivity analysis.
Figure 6 presents the relative change in the three groundwater level residual statistics used in the evaluation of model calibration performance for 10 parameters in the entire EJSWRM for the calibration period. These three groundwater level residual statistics are:
• Root mean square error (RMSE): This statistic is a measure of how spread out the residuals are. • Average residual: This statistic measures how inaccurate simulation results are with respect t o the corresponding observations on average.
• Correlation coefficient (R 2): This statistic is a measure of the strength of the linear relationship between the simulated and observed pairs.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
In the calibrated model residual statistics shown in Figure 5, the RMSE is 10.12 feet, the average residual is -3.01 feet, and the R 2 is 0.93. In Figure 6, the impact of the parameter sensitivity on the average residual from the calibration value of -3.01 feet is always too much of an increase or almost no change. In all the runs, the R2 of 0.93, which ideally would increase in a better calibrated model, either decreases or remains about the same as the calibrated model. Similarly, the RMSE of 10.12 feet would decrease in a better calibrated model; however, all the sensitivity runs either increase or have no impact on the RMSE.
Figure 7 and Figure 8 look at the change in calibration period average ESJ Subbasin change in storage and deep percolation ( both parameters from the hydrologic groundwater budget) . Both figures show h ow sensitive change in storage and deep percolation are to changes in parameters, notably aquifer horizontal hydraulic conductivity (Kh), streambed hydraulic conductivity (Kstr), saturated soil hydraulic conductivity (Ksoil), and target soil moisture (TSM) . Even relatively minor changes to those parameters can have large impacts on the ultimate model results.
None of the sensitivity runs resulted in a significant improvement in statistics or results. This means that the model is stable and that the calibration is at or near an optimal point when global parameter changes are considered.
Figure 6: Sensitivity of Groundwater Level Residual Statistics in Entire ESJWRM
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 7: Sensitivity of Change in Groundwater Storage in ESJ Subbasin
Figure 8: Sensitivity of Deep Percolation in ESJ Subbasin
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
1.3 Historical Model Results
A water budget balances supplies, demands, and a ny 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 revie wed 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 ESJWRM Version 2.0 water budget results are summarized in the following sections.
1.3.1 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 1,262 thousand acre- feet (TAF), consisting of 1,145 TAF agricultural demand and 117 TAF urban demand. This demand was met by an annual average of 5 67 TAF of surface water deliveries ( 512 TAF of agricultural and 5 5 TAF of urban deliveries) and was suppleme nted by 699 TAF of groundwater production (6 38 TAF of agricultural and 62 TAF of urban pumping). The average annual water s hortage for the Subbasin within the calibration period was 5 TAF. Of this annual average, all of the surplus is from agricultural excess and the urban shortage is extremely minor at 0.15 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 9 and Figure 10 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 4 shows the annual averages described above for ESJWRM Version 2.0’s calibration period. Compared to ESJWRM Version 1.1 ESJ Subbasin averages, which had a calibration period through 2015 instead of 2020,
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
the biggest differences in ESJWRM Version 2.0 for the comparable calibration period are in the agricultural land and water use budget. Due to refinements to the agricultural surface water diversions (primarily due to OID , but also due to changes to SSJID, Delta, and riparian diversions ), the surface water deliveries increased by 70 TA F comp ared to ESJWRM Version 1.1 . Additional root zone calibration adjusted agricultural demand for several agencies (OID North, NSJWCD, and SSJID), resulting in ESJWRM Version 2.0 having more demand than ESJWRM Version 1.1. The refinement of delivery groups and estimated diversions reduced the surplus in ESJWRM Version 1.1 by 11 TAF, which resulted in less element pumping in ESJWRM Version 2.0. For the urban budget, the refinement of delivery groups (especially for Stockton area urban users), how demand was inpu t into the model, and diversion amounts eliminated the surplus in ESJWRM Version 1.1.
The corresponding land and water use budgets for both agricultural and urban water demands are included for each GSA in Appendix A. OID is separated out into two separate water budgets: North and South . OID North is a GSA and OID South (not a GSA) is part of Modesto Subbasin . LCSD and LCWD do not have any agricultural demand and therefore a figure is not included.
Table 4: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Averages Land and Water Use Budget Component
ESJWRM
Version 2.0
Annual
Average for
WY 1996-
2020
Agricultural Area (thousand acres) 385
Agricultural Demand (TAF) 1,145
Agricultural Groundwater Pumping (TAF) 638
Agricultural Surface Water Deliveries (TAF) 512
Agricultural Surplus (TAF)1 5
Urban Area (thousand acres) 96
Urban Demand (TAF) 117
Urban Groundwater Pumping (TAF) 62
Urban Surface Water Deliveries (TAF) 55
Urban Shortage (TAF)1 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 9: Eastern San Joaquin Subbasin Agricultural Demand
Figure 10: Eastern San Joaquin Subbasin Urban Demand
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
1.3.2 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 s ubbasins 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 709 TAF of pumping, offset by 262 TAF of deep percolation, a net gain from stream of 129 TAF, 169 TAF of other recharge, and a net boundary inflow of 1 13 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 37 TAFY. These averages are shown in Table 5 and the Subbasin annual groundwater budget is shown in Figure 11.
Table 5 shows the annual averages described above for ESJWRM Version 2.0’s calibration period. The average annual change in storage estimation determined using ESJWRM Version 1.1 was 41 TAF. The latest update and calibration of the model to ESJWRM Version 2.0 has refined this estimate to an average annual change in storage of 37 TAF over the extended calibration period through 2020 . The difference in these estimates is due in large part to the difference in the calibration period, as well as the overhaul of surface water data, especially with regards to OID, and the update to the overall model calibration. This difference in change in storage is well within the ranges observed in the sensitivity analysis discussed in Section 1.2.3.
Other differences observed in the groundwater budget between ESJWRM Version 2.0 and ESJWRM Version
1.1, using the comparable calibration period, are an increase in deep percolation in ESJWRM Version 2.0, most likely caused by increased applied surface water and changes to the root zone calibration, and a decrease in net stream seepage in ESJWRM Version 2.0 due to changes in groundwater levels near streams caused by other groundwater budget components.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 5: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Averages Hydrologic Groundwater Budget Component
ESJWRM
Version 2.0
Annual
Average for
WY 1996-2020
Deep Percolation (TAF) 262
Other Recharge (TAF) 169
Net Stream Seepage (TAF) 129
Net Boundary Inflow (TAF) 113
Groundwater Pumping (TAF) 709
Change in Groundwater Storage (TAF) 37
Figure 11: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
2 Projected Conditions Baseline Update
The refinements and enhancements made to the historical data for the updated historical calibration ESJWRM (ESJWRM Version 2.0) 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 ESJWRM Version 2.0 extended dataset and calibration results is referred to as PCBL Version 2.0. This section presents the key data sources and assumptions used to develop the PCBL Version 2.0 and provides the mo del results.
The PCBL used to develop the projected water budget s 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.
2.1 Assumptions Used to Develop Projected Conditions Baseline Update This section discusses the assumptions made in converting PCBL Version 1.0 to PCBL Version 2.0. The data and calibration parameters were updated to be consistent with the historical ESJWRM Version 2.0. Initial groundwater levels and soil conditions in the PCBL represent those at the end of the simulation period of the historical ESJWRM Version 2.0 (September 30, 2020).
2.1.1 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 uses 52 years of hydrology data from water years 1969 through 2020 (October 1968 through September 30, 2020). The projected 52 years of hydrology used in PCBL Version 2.0 was maintained and extended to meet the SGMA requirements to evaluate how the Subbasin’s surface and groundwater systems may react under representative hydrologic conditions.
2.1.1.1 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 2.0. Figure 12 shows the Subbasin annual precipitation (blue columns), average precipitation (green line) of approximately 15 inches, and cumulative departure from mean precipitation (orange line) for each water year from 1969 through 2020 . 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 a nalyzed, 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.
Each year on the x -axis in Figure 12 is indicated with the San Joaquin Valley Water Year Hydrologic Classification Index published by DWR. The 52 years of the PCBL, from WY 1969 through 2020, represent a range of hydrologic conditions, as identified by the water year t ypes in the San Joaquin Valley Water Year Hydrologic Classification, which classifies water years 1901 through 2020 as Wet (W), Above Normal (AN),
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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. In the 52 years of hydrology used in the PCBL Version
2.0, there are 14 Critical years, 9 Dry years, 4 Below Normal years, 7 Above Normal years, and 18 Wet years.
Figure 12: Historical Precipitation in Eastern San Joaquin Subbasin
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 23 Dry years, 11 Normal years, and 18 Wet years. These baseline water year types (Table 6) are used in the remainder of the PCBL data development and results discussion.
As evident in Figure 12, there are three periods of extreme drought in which there are sequences of critical years where the cumulative departure from mean precipitation drops signific antly in a steep slope . To capture future extreme dry year periods that may occur in the PCBL, the following 10 water years were designated as Drought periods: 1976 -1977, 1987-1992, and 2014 -2015. Drought years are highlighted in red on the x -axis of Figure 12 and distinguished in Table 6. Though the most recent drought lasted fro m 2012 through 2015, the selected baseline drought years only included 2014 and 2015 as those were the most critical years in which supplies and demands were most impacted.
An 11-year period (WY 2010-2020) 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
historical data in ESJWRM Version 2.0 during these years and because the distribution of water year types was relatively consistent with the overall PCBL hydrology.
Table 6: Baseline Hydrologic Water Year Types
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 27 1995 Wet Wet
2 1970 Above Normal Normal 28 1996 Wet Wet
3 1971 Below Normal Normal 29 1997 Wet Wet
4 1972 Dry Dry 30 1998 Wet Wet
5 1973 Above Normal Normal 31 1999 Above Normal Normal 6 1974 Wet Wet 32 2000 Above Normal Normal
7 1975 Wet Wet 33 2001 Dry Dry
8 1976 Critical Drought 34 2002 Dry Dry
9 1977 Critical Drought 35 2003 Below Normal Normal
10 1978 Wet Wet 36 2004 Dry Dry
11 1979 Above Normal Normal 37 2005 Wet Wet
12 1980 Wet Wet 38 2006 Wet Wet
13 1981 Dry Dry 39 2007 Critical Dry
14 1982 Wet Wet 40 2008 Critical Dry
15 1983 Wet Wet 41 2009 Below Normal Normal
16 1984 Above Normal Normal 42 2010 Above Normal Normal 17 1985 Dry Dry 43 2011 Wet Wet
18 1986 Wet Wet 44 2012 Dry Dry
19 1987 Critical Drought 45 2013 Critical Dry
20 1988 Critical Drought 46 2014 Critical Drought
21 1989 Critical Drought 47 2015 Critical Drought
22 1990 Critical Drought 48 2016 Dry Dry
23 1991 Critical Drought 49 2017 Wet Wet
24 1992 Critical Drought 50 2018 Below Normal Normal
25 1993 Wet Wet 51 2019 Wet Wet
26 1994 Critical Dry 52 2020 Dry Dry
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
2.1.1.2 Evapotranspiration
No changes to evapotranspiration in ESJ Subbasin were implemented in PCBL Version 2.0. ESJWM Version
2.0 evapotranspiration by land use type and by model subregion is assumed to be consistent into the future.
2.1.1.3 Streamflow
No change was assumed in PCBL Versi on 2.0 to all stream inflows. SSJID system outflows were calculated based on the 11-year aggregated water year type average of historical data for WY 2010-2020.
2.1.2 Land Use and Cropping Patterns
PCBL Version 2.0 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 model-wide land use survey from DWR (DWR, 2018d), 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 sam e edits were made to elements representing LCSD and LCWD to remove agricultural land, as described above for ESJWRM Version 2.0 discussed in Section 1.1.5. The land use data for OID area is adjusted to reflect the information consistent with the OID AWMP.
To represent the extent of urban buildout in 2040, the urban areas in 2018 land use dataset were expanded to either the sphere of influence or general plan boundarie s and are held constant during the simulation.
The areas with urban buildout are shown in Figure 13 and 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 la nd 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, c ropping 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 34,000 acres and undeveloped acreage decreases by under 15,000 acres. Table 7 shows the differences between the DWR 2018 data and the ultimate baseline acreage once urban buildout was incorporated. Figure 14 is a pie chart of the PCBL Version 2.0 cropping pattern.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 13: 2018 Land Use with Urban Sphere of Influence Boundaries
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 7: ESJ Subbasin Land Use Acreages by Land Use Type Land Use Type DWR 2018
Survey Baseline Model Change from
DWR 2018 Survey
Ag Acreage 392,112 358,340 -33,772
Urban Acreage 104,858 153,484 48,625
Undeveloped
Acreage 255,143 240,289 -14,853
Riparian 12,579 12,579 0
Figure 14: 2018 Cropping Pattern for ESJ Subbasin
2.1.3 Water Supply and Demand
Urban water demand in the PCBL Version 2.0 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 20 20 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 t he 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 the purpose of the modeling, supply was assumed to meet the demand with no surplus.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Agricultural water supply largely used the 11 -year averages of grouped water year types from the recent historical data (WY 2010 -2020). All PCBL annual average surface water diversion volumes are included in Table 2.
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.
2.2 Projected Conditions Baseline Results
This section provides a summary of the ESJWRM PCBL Version 2.0 results.
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 projected water demand for the Subbasin within the 52-year simulation period is 1,258 thousand acre-feet (TAF), consisting of approximately 1,100 TAF expected agricultural demand and 158 TAF expected urban demand. This demand is met by an annual average of 528 TAF of surface water deliveries (453 TAF of agricultural and 76 TAF of urban deliveries) and is supplemented by 743 TAF of groundwater production (661 TAF of agricultural and 82 TAF of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 13 TAF 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 suppl y (groundwater pumping an d 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 8. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 15 and Figure 16 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.
The corresponding average annual agricultural and urban demand figures for the projected conditions baseline are included for each GSA in Appendix B. As in the historical model LCSD and LCWD do not have projected agricultural demand and therefore the figure is not included. At full buildout to the sphere of
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
influence boundaries, City of Stockton GSA, San Joaquin County #2, and City of Manteca GSA do not have agricultural demand and therefore figures for those GSAs are also not included.
Table 8: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Land and Water Use Budget Component
PCBL
Version 2.0
Annual
Average
Agricultural Area (thousand acres) 359
Agricultural Demand (TAF) 1,100
Agricultural Groundwater Pumping (TAF) 661
Agricultural Surface Water Deliveries (TAF) 453
Agricultural Surplus (TAF)1 13
Urban Area (thousand acres) 153
Urban Demand (TAF) 158
Urban Groundwater Pumping (TAF) 82
Urban Surface Water Deliveries (TAF) 76
Urban Shortage (TAF)1 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 d emands. 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 15: Eastern San Joaquin Subbasin Projected Agricultural Demand
Figure 16: Eastern San Joaquin Subbasin Projected Urban Demand
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 Version 2.0 remains the largest component in the groundwater budget with an annual average 751 TAF. The PCBL offsets this pumping with 282 TAF of deep percolation, a net gain from stream of 181 TAF, 162 TAF of other recharge, and a total subsurface inflow of 110 TAF 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, al l 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 is 16 TAFY. These annual averages are shown in Table 9. The groundwater budgets, with average cumulative change in storage, are shown for the ESJ Subbasin in Figure
17. Table 9: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Hydrologic Groundwater Budget Component
PCBL
Version 2.0
Annual
Average
Deep Percolation (TAF) 282
Other Recharge (TAF) 162
Net Stream Seepage (TAF) 181
Net Boundary Inflow (TAF) 110
Groundwater Pumping (TAF) 751
Change in Groundwater Storage (TAF) 16
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 17: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3 Projected Conditions Baseline Update with Climate Change With the update of the PCBL Version 2.0, the potential impact of climate chang e 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 is referred to as PCBL-CC Version 2.0.
Largely, PCBL-CC Version 1.0 and Vers ion 2.0 use the same perturbation factors, but PCBL -CC Version 2.0 extends the simulation time period by two years. This section presents the climate change methodology, data sources, and assumptions used to develop the PCBL-CC Version 2.0 and provides the model results.
In PCBL-CC Version 1 .0, the ESJGWA decided to use 20 70 Central Tendency perturbation factors as a reasonable estimation of the impact of climate change. PCBL-CC Version 2.0 also used 2070 Central Tendency climate change conditions.
3.1 Climate Change Background and Methods
SGMA requires taking into consideration uncertainties associated with climate change in the development of GSPs.
Consistent with Sec tion 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.”
3.1.1 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 guid ance document ( CA DWR, 2018b ). The “best available
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
information” related to climate change in the Eastern San Joaquin 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:
• 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 (CA DWR, 2018c). The guidance document details the approach, development, applications, and limitations of the datasets available from the SGMA Data Viewer (CA DWR, 2018c). The Water Budget BMP describes in greater detail how DWR recommends projected water budgets with climate change be estimated (CA DWR, 2016). The Desktop IWFM Tools are available to estimate the projected precipitation and evapotranspiration inputs under climate change conditions (CA DWR, 2018b).
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 18 shows the overall process developed for the Subbasin consistent with the Climate Change Resource Guide (CA DWR, 2018b) and describes workflow beginning with projec ted conditions inputs and assumptions to perturbed 2070 conditions for the projected conditions.
Figure 18: Eastern San Joaquin Climate Change Analysis Process The process described in Figure 18 of developing a projected water budget with and without climate change was discussed with DWR staff 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 10: DWR-Provided DatasetsTable 10 summarizes the forecasted variable datasets provided by DWR that were used to carry out the climate change analysis (CA DWR, 2018b). The Variable Infiltration Capacity (VIC) model referred to in Table 10 is the fully mechanistic hydrologic model used by DWR to derive hydrographs under standard and climate change conditions.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 10: DWR-Provided Datasets
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
3.1.2 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 Eastern San Joaquin Subbasin, sea level rise was not included.
The method for perturbing the streamflow, precipitation, and evapotranspiration input files is descr ibed in the following sections. A future scenario of 2070 climate forecasts was evaluated in this analysis, consistent with DWR guidance (CA DWR, 2018b). 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 (CA DWR, 2018b). The 2070 central tendency amo ng 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 2.0 completed as part of the 2021 update of the historical and projected conditions model.
This PCBL Version 2.0 has a 52-year simulation baseline period with hydrology from WY 2019 and WY 2020 incorporated. Updates to the PCBL are documented in Section 2. Model results from the updated PCBL-CC are reported in Section 3.3.
3.2 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.2.1 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 surfa ce 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 t he state are not used directly. Instead, relative perturbation factors were used to derive surface water inflows and diversions for use in ESJWRM.
Local tributaries and smaller streams within Eastern San Joaquin 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 (CA DWR, 2018b). Therefore, Mokelumne River flows used the perturbation factor method for consistency with the methodology applied to smaller streams. 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 11Table 11: Eastern San Joaquin Stream Inflows presents the impaired and unimpaired streams in the ESJWRM for the Eastern San Joaquin Subbasin.
Table 11: Eastern San Joaquin Stream Inflows
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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.2.1.1 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; howev er, the model hydrologic period runs from Water Year 1969-2018. 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 (CA DWR, 2018a).
DWR uses five designations ranging from driest to wettest conditions: Critical, Dry, Below Normal, Above Normal, and Wet. Table 12Table 12: San Joaquin Valley Water Year Type Designations below shows the year type designations used to synthesize the remaining years (2011-2018).
The PCBL with climate change scenario reported in the GSP only used hydrology baseline years through 2018. In the updated PCBL-CC reported in this TM, WY 2019 and WY 2020 are incorporated and added to Table 12 below. The climate change perturbation was carried out for the two additional years of simulation using methods consistent with how the rest of the synthesized years were calculated in the GSP fo r unimpaired streamflows.
As part of the update to the PCBL, 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.
Table 12: 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
2013 Critical
2014 Critical
2015 Critical
2016 Dry
2017 Wet
2018 Below Normal
2019 Wet
2020 Dry
Figure 19 shows the perturbed time series against the projected conditions scenario time series for Dry Creek through the 52 -year simulation period and Figure 20 presents the exceedance probability curve.
Figure 21 and Figure 22 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.
Figure 19: Dry Creek Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 20: Dry Creek Exceedance Curve
Figure 21: Mokelumne River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 22: Mokelumne River Exceedance Curve
3.2.1.2 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 -2018, streamflow was synthesized based on flows from WY 1969-2003 and the DWR year type index shown in Table 12 (CA DWR, 2018a). 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 sim ilar 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. Therefo re, 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 betwe en 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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 in flows 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 two additional years of simulation using methods consistent with how the rest of the synthesized years were calculated in the GSP for impaired streamflows.
Figure 23 through Figure 28 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 52-year simulation.
Figure 29 through Figure 32 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.
Figure 23: Calaveras River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 24: Calaveras River Exceedance Curve
Figure 25: Stanislaus River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 26: Stanislaus River Exceedance Curve
Figure 27: San Joaquin River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 28: San Joaquin River Exceedance Curve
Figure 29: Tuolumne River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 30: Tuolumne River Exceedance Curve
Figure 31: Cosumnes River Hydrograph
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 32: Cosumnes River Exceedance Curve
3.2.2 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 (CA DWR, 2018b).
DWR used a macroscale hydrologic model that so lves 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 Detrend ed 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 (CA DWR, 2018c).
3.2.2.1 Applying Change Factors to Precipitation
DWR change factors were multiplied by historical precipi tation to generate projected precipitation under the 2070 central tendency future scenario using the Desktop IWFM GIS tool (CA DWR, 2018c). 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 6 years of the time series were synthesized according to his torically comparable water years. The perturbation factor from the corresponding month of the comparable year was applied to the baseline of the missing years (2012-2018) to generate projected values. Months with no precipitation in the baseline were assumed to have a monthly
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 13. These comparable years were determined by comparing total San Joaquin Valley runoff, DWR year type index, and total annual Subbasin precipitation.
The same approach reported in the GSP to synthesizing years that are not included in the DWR dataset was used to extend the simulation for two additional years. The comparable water years used to represent WY 2019 and WY 2020 hydrology have been added to Table 13 below.
Table 13: Comparable Water Years (based on Precipitation) 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
The resulting perturbed precipitation values and the baseline precipitation values for the representative historical period can be found in Figure 33. The exceedance plot for these two times series can be found in Figure 34, both updated for 52 years of projected conditions simulation . The absolute difference between the PCBL-CC and the PCBL are shown in Figure 35.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 33: Perturbed Precipitation Under Climate Change
Figure 34: Perturbed Precipitation Exceedance Curve
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 35: Subbasin Precipitation Difference with Climate Change Conditions
3.2.2.2 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 o f 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, as shown for vineyards in Error! Reference source not found..
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 36 through Figure 38.
There were no changes made to the projected conditions simulation for evapotranspiration in the PCBL 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 52 year simulation.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 36: Monthly Evapotranspiration Variability for Almonds
Figure 37: Monthly Evapotranspiration Variability for Walnuts
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 38: Monthly Evapotranspiration Variability for Cherries
Figure 39: Monthly Evapotranspiration Variability for Vineyards
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.3 Projected Conditions Baseline with Climate Change Results This section provides a summary of the ESJWRM PCBL-CC Version 2.0 results.
3.3.1 Differences in Precipitation, Evapotranspiration, and Streamflow under Climate Change
Under the climate change scenario (PCBL-CC), the average annual precipitation is overall 10 percent higher than the projected conditions scenario (PCBL), increasing from 985,000 AFY to 1,082,000 AFY or from about
15.5 in/year to 17.0 in/year. Similarly, the average annual volume of evapotranspiration in PCBL-CC is 8 percent higher than the PCBL, increasing to 1,441,000 AFY from 1,362,000 AFY. Despite there being higher flows in streams in PCBL-CC, the anticipated surface water diversions were not expected to change in PCBL- CC 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, private groundwater production is simulated to increase by approximately 10 percent, from 751,000 AFY to 833,000 AFY. Under climate change conditions, due to increased groundwater use d riven by higher agricultural demands, the depletion in aquifer storage is expected to increase by about 134 percent to an average annual storage change of 38,000 AFY in the PCBL-CC, from 16,000 AFY in the PCBL. A graphical representation of simulated changes to precipitation, evapotranspiration, and groundwater pumping are presented in Error! Reference source not found. though Error! Reference source not found. . Full water budgets for the land surface and groundwater systems are discussed in Sections 3.3.2 and 3.3.3.
Figure 40: Simulated Changes in Precipitation due to Climate Change
Note: Negative indicates PCBL value was larger and positive indicates PCBL-CC was larger. The climate change scenario largely has more precipitation than the projected conditions scenario.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 41: Simulated Changes in Evapotranspiration due to Climate Change
Note: PCBL-CC evapotranspiration is always larger than the PCBL for all simulated years.
Figure 42: Simulated Changes in Groundwater Pumping due to Climate Change
Note: PCBL-CC groundwater pumping is always larger than the PCBL for all simulated years.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.3.2 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 agricu ltural 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 52-year simulation period is 1,339 thousand acre-feet (TAF), consisting of approximately 1,181 TAF expected agricultural demand and 158 TAF expected urban demand. This demand is met by an annual average o f 528 TAF of surface water deliveries (452 TAF of agricultural and 76 TAF of urban deliveries) and is supplemented by 825 TAF of groundwater production (742 TAF of agricultural and 82 TAF of urban pumping). Due to uncertainties in the estimation of projected agricultural demand and historical supply records, there is 13 TAF 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 14. The annual land and water use budgets across the ESJ Subbasin are shown in Figure 43 and Figure 44 for the Subbasin as a whole, showing the agricultural and urban, respectively, demands plotted with water supplies.
A comparison between the PCBL and the PCBL-CC is included in Table 15. As shown in Section 3.3.1 and Figure 41, evapotranspiration is higher in the PCBL -CC compared to the PCBL in every year of the simulation. This higher evapotranspiration translates to a higher agricultural demand in the PCBL-CC of 81,400 AFY, which must be met by increased groundwater pumping of 81,800 AFY. The slight difference between the demand increase and the groundwater pumping increase is due to a decrease in 400 AFY of agricultural surface water deliveries . Small changes in surface water availability in streams occurred in the PCBL -CC compared to the PCBL 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 versus the PCBL, aside from a minor difference in surface water diversions that was balanced by a small increase in urban shortage.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 14: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average for
PCBL-CC
Land and Water Use Budget Component
PCBL-CC
Annual
Average
Agricultural Area (thousand acres) 359
Agricultural Demand (TAF) 1,181
Agricultural Groundwater Pumping (TAF) 742
Agricultural Surface Water Deliveries (TAF) 452
Agricultural Surplus (TAF) 13
Urban Area (thousand acres) 153
Urban Demand (TAF) 158
Urban Groundwater Pumping (TAF) 82
Urban Surface Water Deliveries (TAF) 76
Urban Shortage (TAF) 0
Table 15: Eastern San Joaquin Subbasin Land and Water Use Budget Annual Average Comparison Between the PCBL and the PCBL-CC
Annual Average
Land and Water Use Budget
Component PCBL PCBL-CC
Climate Change
Impact (PCBL-CC
minus PCBL)
Agricultural Area (acres) 358,600 358,600 0
Agricultural Demand (AF) 1,099,900 1,181,300 81,400
Agricultural Groundwater Pumping (AF) 660,600 742,400 81,800 Agricultural Surface Water Deliveries (AF) 452,800 452,400 -400 Agricultural Surplus (AF) 13,500 13,500 0
Urban Area (acres) 153,400 153,400 0
Urban Demand (AF) 158,100 158,100 0
Urban Groundwater Pumping (AF) 82,200 82,200 0
Urban Surface Water Deliveries (AF) 75,600 75,500 -100
Urban Shortage (AF) 300 400 100
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 43: Eastern San Joaquin Subbasin Projected Agricultural Demand in the PCBL-CC
Figure 44: Eastern San Joaquin Subbasin Projected Urban Demand in the PCBL-CC
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
3.3.3 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 remains the largest component in the groundwater budget with an annual average 833 TAF. The PCBL -CC offsets this pumping with 28 6 TAF of deep percolation, a net gain from stream of 218 TAF, 165 TAF of other recharge, and a total subsurface inflow of 126 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 is 38 TAFY. These annual averages are shown in Table 16. The groundwater budget, with cumulative change in storage, is shown for the ESJ Subbasin in Figure 45.
A comparison of the PCBL and the PCBL-CC is shown in Table 17. The increase in groundwater pumping of 81,800 AFY is due to the increase in evapotranspiration and therefore increased agricultural demand as discussed above in Section 3.3.2 and
Table 15. Additionally, increase d precipitation in most years as shown in Error! Reference source not found. and discussed in Section 3.3.1, leads to overall increased deep percolation from precipitation and other recharge (spe cifically 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 PCBL -CC, which may also allow for more stream seepage into the groundwater system.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Table 16: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Hydrologic Groundwater Budget
Component
PCBL-CC Annual
Average
Deep Percolation (TAF) 286
Other Recharge (TAF) 165
Net Stream Seepage (TAF) 218
Net Boundary Inflow (TAF) 126
Groundwater Pumping (TAF) 833
Change in Groundwater Storage (TAF) 38
Table 17: Eastern San Joaquin Subbasin Hydrologic Groundwater Budget Annual Average Comparison Between the PCBL and the PCBL-CC
Annual Average
Hydrologic Groundwater Budget
Component PCBL PCBL-CC
Climate Change
Impact (PCBL-CC
minus PCBL)
Deep Percolation (AF) 282,100 285,600 3,500
Other Recharge (AF) 161,700 165,300 3,600
Net Stream Seepage (AF) 180,700 218,100 37,400
Net Boundary Inflow (AF) 110,400 126,000 15,700
Groundwater Pumping (AF) 751,300 833,100 81,800
Change in Groundwater Storage (AF) 16,300 38,100 21,800
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Figure 45: Eastern San Joaquin Subbasin Projected Hydrologic Groundwater Budget
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
4 Conclusions and Recommendations
The updated ESJWRM Version 2.0 is a robust, com prehensive, defensible, and well-established model for assessing the water resources in the ESJ Subbasin under historical and projected conditions using PCBL Version 2.0 . 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 s eries of ET values for use in the model.
• Refine infiltration of precipitation . The current version of the IDC is based on parameters from the DWR C2VSim model. Further refinements can be made to reflect the local soil conditions and rainfall runoff patterns.
• Refine surface water deliveries in Cosumnes Subbasin. The surface water deliveries in the Cosumnes Subbasin are currently at the subregion level and do not have the detailed spatial resolution of other areas within the ESJ Subbasin. This data may be ver ified and updated with modeling in that subbasin completed to meet the requirements of SGMA. • Update land use as needed. As part of the statewide SGMA support, the DWR prepares statewide land use surveys every other year. It is recommended that the appropri ate land use surveys be incorporated in the historical model, as well as the projected baseline as necessary and needed. • Integration with GRAT . ESJGWA is in the process of developing a Groundwater Recharge Assessment Tool (GRAT). It is recommended to integrate the ESJWRM with the GRAT to better assess the implications of any water recharge on the state of the basin and distribution of benefits. • Climate change refinement. The approach developed for the GSP and used in the PCBL -CC Version 2.0 update is based on the methodology in DWR’s guidance document (CA DWR, 2018b) and uses “best available information” related to climate change in the Eastern San Joaquin 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.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
5 References
California Department of Finance (DOF). Downloaded March 2021. E-4 Population Estimates for Cities, Counties, and the State, 2011 -2020 with 2010 Census Benchmark.
https://www.dof.ca.gov/Forecasting/Demographics/Estimates/e-4/2010-21/.
Department of Water Resources. 2016. Best Management Practices for the Sustainable Management of Groundwater Water Budget.
Department of Water Resources (DWR). Statewide Crop Mapping 2016. Downloaded for groundwater subbasins in model area. https://gis.water.ca.gov/app/CADWRLandUseViewer/.
Department of Water Resources (DWR). 2018a. Chronological Reconstructed Sacramento and San Joaquin Valley Water Year Hydrologic Classifications Indices.
Department of Water Resources (DWR) . 2018b. Guidance for Climate Change Data Use During Groundwater Sustainability Plan Development.
Department of Water Resources (DWR). 2018c. SGMA Data Viewer.
Department of Water Resources (DWR). 2018d. Statewide Crop Mapping 2018. Downloaded for groundwater subbasins in model area. https://gis.water.ca.gov/app/CADWRLandUseViewer/.
Dogrul, Emin C. and Tariq N. Kadir . 2021a. Integrated Water Flow Model Theoretical Documentation (IWFM - 2015), Revision 1273. Bay-Delta Office, California Department of Water Resources. September 2021. https://data.cnra.ca.gov/dataset/iwfm-integrated-water-flow-model/resource/64b1047a-39ff-46db-8b93- 1e6f95e50865.
Dogrul, Emin C. and Tariq N. Kadir. 2021b. DWR Technical Memorandum: Theoretical Documentation and User’s Manual for IWFM Demand Calculator (IDC-2015), Revision 1273. Bay-Delta Office, California Department of Water Resources. September 2021. https://data.cnra.ca.gov/dataset/iwfm-integrated-water-flow- model/resource/64b1047a-39ff-46db-8b93-1e6f95e50865.
Doherty, J., 2015. Calibration and Uncert ainty Analysis for Complex Environmental Models. Watermark Numerical Computing, Brisbane, Australia. ISBN: 978-0-9943786-0-6.
Eastern San Joaquin Groundwater Authority (ESJGWA). 2019. Eastern San Joaquin Groundwater Subbasin Groundwater Sustainability Plan. November 2019.
Lockeford Community Services District (LCWD). 2016. Final Lockeford Community Services District Municipal Services Review. Prepared for San Joaquin County Local Agency Formation Commission. September 2016.
Oakdale Irrigation District (OID) . 2021. 2020 Agricultural Water Management Plan. Prepared by Davids Engineering. March 2021.
Oregon State University (OSU). Downloaded March 2021. PRISM Climate Group. http://prism.oregonstate.edu.
South San Joaquin Irrigation District (SSJID) . 2021. 20 20 Agricultural Water Management Plan. Prepared by Davids Engineering. Adopted March 23, 2021.
Woodard & Curran. 2018a. Eastern San Joaquin Water Resources Model (ESJWRM) Final Report. August 2018 .
Woodard & Curran. 2018b. Eastern San Joaquin Water Resourc es Model Agricultural and Urban Demand Estimates Technical Memorandum. February 2018.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 1 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
TECHNICAL MEMORANDUM NO. 2 – Drinking Water &
Shallow Wells
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Matt Zidar, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Leslie Dumas and Natalie Cochran/Woodard & Curran DATE: June 24, 2022
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s November 18, 2021 Consultation Initiation Letter - Response to DWR Deficiency 1(d) and 1(e) and Corrective Actions
The Eastern San Joaquin Groundwater Authority (ESJGWA or GWA) received a Consultation Initiation Letter (Letter) on November 18, 2021 (Attachment 1), from the California Department of Water Resources (DWR).
The Letter identified two potential deficiencies wi th the Eastern San Joaquin Groundwater Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) which may preclude DWR’s approval, as well as potential corrective actions to address each potential deficiency. The Letter thus initiated consultation between DWR, the Plan Manager, and the Subbasin’s groundwater sustainability agencies (GSAs) regarding the amount of time needed to address the potential deficiencies and corrective actions. A subsequent meeting with DWR was held on April 4, 2022 to discuss the Subbasin’ s proposed approach to a ddressing the identified deficiencies. The analysis presented in this memorand um was completed in response to the Letter, based on direction provided by the ESJGWA, the Subbasin GSAs and DWR. It is intended to supplement the Eastern San Joaquin GSP that was submitted in January 2020 and fill potential gaps identified in the Letter provided by DWR.
Deficiency 1, as described in the DWR November 18, 2021 letter, is summarized as follows:
Potential Deficiency 1: The GSP lack s sufficient justification for determining that undesirable results for chronic lowering of groundwater levels, subsidence, and depletion of intercon nected 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.
The letter then went on to identify six potential corrective actions that could address this deficiency. This Technical Memorandum (TM) was prepared to address th e deficiency as described in Potential Correction Actions 1(d) and 1(e) which states the following:
“1(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 region al hydrologic conditions. In that scenario, the
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 2 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
GSAs should explain the ration ale 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 unreas onable. 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 th resholds and describe anticipat ed effects of the thresholds on beneficial uses and users of groundwater. Furt hermore, the GSAs should explain whether other drinking water users that may rely on shallow we lls, 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.
1(e) The GSAs should revise the GSP to describe how they would addr ess 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 di scussion, 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.” The following subsections provide a response to each of the Potential Corrective Action subparts listed above, and include a discussion with supplemental information, analysis, justification, and data needed to support the GSP and address each issue identified.
Potential Corrective Action 1(d)-1: Explain the rationale for determining groundwater levels can exceed those thresholds at 25% of monitoring sites for two consecutive years before the effects would be considered significant and unreasonable.
Initial Review Provided by DWR
The Letter states 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. 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.” As a Potential Corrective Action, the following is suggested: “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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 3 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
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.” Supplemental Information in Response to DWR Letter
Explanation of Rationale For Threshold Exceedance
Refer to “Response to DWR Deficiency 1(a) and 1( b)” technical memorandum for discussion regarding removal of the water-year type requirement from the definition of an undesirable result for the chronic lowering of groundwater levels minimum threshold. As noted in this TM, the revised definition of an undesirable result for the chronic lowering of gr oundwater levels is when at least 25 percent of representative monitoring wells used to monitor groundwater levels (5 of 20 representative monitoring wells in the Subbasin) fall below their minimum level th resholds for two consecutive years. Significant and unreasonable impacts that may oc cur when the minimum thresholds are exceeded for more than two consecutive years includes de-watering of a subset of the existing groundwater infrastructure, starting with the shallowest wells, which are generally domestic wells, and adverse effects on GDEs .
Two consecutive years of minimum threshold exceedance s are used to determine if an undesirable result has occurred to establish a pattern rather than an isolated event. The lowering of groundwater levels during two consecutive dry or critically-dry years is not considered to be unreasonable unless the levels do not rebound to above the thresholds fo llowing wet conditions or are otherwise mitigated through adaptive management or implementation of projects and management actions. While statistically, three data points are required to establish a tr end, three years of exceedances was felt to be too extreme, whereas a single exceedance was not sufficient to establish a trend. Therefore, the two consecutive years was selected as part of this definition.
At least 25 percent of representative monitoring wells used to monitor groundwater levels falling below their minimum thresholds for two consecutive years was presented to the Eastern San Joaquin Technical Advisory Committee (ESJ TAC) during the April 10, 2019 meeting and was appr oved by the Eastern San Joaquin Groundwater Authority (ESJGWA) Board during the May 8, 2019 meeting. Opportunity was available for public comment during the Public Draft GSP 45-day review period from July 10, 2019 to August 25, 2019. The Eastern San Joaquin Water Resources Model (ESJWRM) results under th e projected conditions baseline scenario were used to evaluate minimum threshold exceedances, and the model results considered in determining that a 25 percent exceedance threshold was sufficient to determine that undesirable results would occur subbasin-wide (e.g., were not a localized event).
As the GSP is implemented, the defin ition of undesirable results for th e chronic lowering of groundwater sustainability indicator, as well as all other applicable sustainability indicators, will continue to be evaluated to determine it supports the sustainability goal of the Subbasin.
Potential Corrective Action 1(d)-2: Explain how other factors they identified as "potential undesirable results" (e.g., adverse impacts to environmental uses and users) factored into
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 4 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
selecting minimum thresholds and describe anticipated effects of the thresholds on beneficial uses and users of groundwater
Initial Review Provided by DWR
The Letter states the GSP “…builds an analysis of domestic wells going dry into its minimum thresholds, thereby considering the fact ors 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 pumpin g capacity or increased pumping costs for shallow groundwater users, or adverse impacts to environmental uses and users.” As a Potential Corrective Action, the following is suggested: “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.”
Supplemental Information in Response to DWR Letter
Explanation of Other Factors in Potential Undesirable Results During GSP development (and as stated under Section 3.2.1.1.1 of the GSP), potential undesirable results identified by stakeholders included a 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 Adverse impacts to environmental uses and user s, including interconne cted surface waters and groundwater-dependent ecosystems (GDEs)
As stated under Section 3.2.1.2 of the GSP, the minimum thresholds for chronic lowering of groundwater levels are the shallower at each representative monitoring well site of the following:
The deeper of 1992 and 2015-2016 historical groundwater levels with a buffer of 100 percent of historical range applied, or
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 5 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
The 10th percentile domestic well total depth of wells within a 3-mile radius of the monitoring well.1,2 To develop these thresholds, members of the ESJGWA Board, TAC, and Workgroup evaluated the potential for undesirable results based on past , present, and future conditions. In addition to anecdotal on-the- ground data, data from DWR and Subbasin GSAs, as well as information from reports and planning documents, were used to identify how a given area falls into any one of three general conditions: 1) Areas with significant and unreasonable existing issues, 2) Areas that previously had issues, and 3) Areas that have never had issues. Each of the three conditions correspond to a diffe rent pathway to setting minimum thresholds. Classification of the various areas were based on input from GSAs and stakeholders and review of prior planning documents.
Areas with significant and unre asonable existing issues: thes e areas are considered to have undesirable results, and minimum thresholds ar e set to 2015 in accordance with Sustainable Groundwater Management Act (SGMA) legislation. No areas were identified by the ESJGWA Board or other stakeholders under this condition within the Subbasin. Areas that previously ha d significant and unreasonable issues : for areas with historical but not current significant and unreasonable results (as identified by GSAs, stakeholders, and prior planning documents), historical levels were considered in the development of minimum thresholds in addition to existing basin management criteria.
Areas that have never had signif icant and unreasonable issues: in areas that have never had recognized issues (e.g., cones of depression), discussions on what the ESJGWA would consider to be significant and unreasonable drove identification of potential thresholds, and minimum thresholds were developed based on the preservation of future beneficial uses.
The ESJGWA Board and Advisory Co mmittee reviewed previously adopte d groundwater-related planning documents including the 2014 ESJ Integrated Regional Water Management Plan (IRWMP), the 2004 Groundwater Management Plan (GMP), Agricultural Water Management Plans (AWMPs), and the Mokelumne Watershed Interregional Sustainability Evaluation (MokeWISE) Water Program. These
1 A radius of 2 miles was used for well 0307E21L003 to reflect domestic well depths in close proximity to the Mokelumne River.
2 In municipalities with ordinances requiring the use of City water (water provided by the City’s municipal wells), the 10th percentile municipal well depth is used in place of the 10th percentile domestic well depth criteria.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 6 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
documents provided a starting point for setting mi nimum thresholds. The ESJ IRWMP indicates fall 1992 groundwater elevation levels as a historically low benchmark for the Subbasin, stating “The Eastern San Joaquin Groundwater Basin contour measured in 1992 is proposed as the basin management framework baseline. Groundwater fell to its lowest recorded elev ation in 1992 following a si gnificant drought period and it is considered undesirable to drop below this level” (Eastern San Joaquin County GBA, 2014). This language, although developed within the SGMA framework, has severed as a starting point for developing minimum thresholds under SGMA.
Fall 1992 groundwater levels were examined and compared to levels following the recent drought (fall 2015- 2016) using groundwater elevation da ta from officially monitored California Statewide Groundwater Elevation Monitoring (CASGEM) wells, voluntarily monitored CASGEM wells, clustered and nested wells, and San Joaquin County database wells (described in fu rther detail in Section 2.1.1.1 of the GSP). This examination showed that groundwate r levels in some areas of the Subbasin have recovered since 1992, with much of the central portion of the Subbasin show ing an increase of greater than 10 feet. However, groundwater levels in other portions of the Subbasi n have further decreased below 1992 levels without undesirable effects being observed by the GSAs and other stakeholders. In many cases, areas that experienced undesirable effects in 1992 put mitigation measures in place, often deepening wells, meaning that 1992 groundwater levels would no longer trigger undesirable effects.
The deepest conditions between fourth quarter 1992 and 2015-2016 groundwater levels were examined to develop a greater understanding of po tential impacts to beneficial uses experienced under historical low groundwater levels. These years were chosen based on the threshold language in the ESJ IRWMP and also to capture the end of the two most recent droughts. Fourth quarter 2014 data were used in the northwest corner of the Subbasin, where data are limited.
Individual GSAs confirmed understan ding of the historical lows based on their experience and data, provided feedback on groundwater conditions for thei r GSAs, and indicated if undesirable results could occur if the minimum threshold wa s set deeper than the deeper of 1992 and 2015-2016 based on their understanding. GSAs then identified potential wells to be included in the representative monitoring network for the groundwater level sustainability indicator bas ed on the adequate spatial coverage, availability of historical data, and reliability of the monitoring well. For the majority of the Subbasin, GSA representatives identified no undesirable results, even if groundwater were to reach historical low groundwater levels. As a starting point, a potential minimum threshold was considered for each representative monitoring well based on the lower of 1992 or 2015-2016 values unless ot herwise indicated. A buffe r was subtracted from the minimum 1992 or 2015 groundwater elevation. The buffer was calculated by finding the difference between the minimum and maximum groundwater level over the historical record for each representative monitoring well. The subtraction of the buffer provides a range in which groundwater levels may continue to decline during implementation of projects and management ac tions until sustainable yield is reached. The buffer allows for flexibility to ac count for natural fluctuations in ground water levels but would avoid significant and unreasonable impacts to groundwater levels.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 7 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
Information used to support development of well-specific minimum thresholds is included in Appendix 3- A and 3-B of the GSP.
Potential Corrective Action 1(d)-3: Explain whether other drinking water users that rely on shallow wells were considered or conduct outreach to shallow well users and incorporate their wells into consideration of site-specific MTs and MOs Initial Review Provided by DWR
The Letter states “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 flexibilit y. 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. 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.” 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.
As a Potential Corrective Action, the following is suggested: “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.”
Supplemental Information in Response to DWR Letter
Explanation of Drinking Water User Consideration
The ESJGWA Board determined that de watering of domestic wells may be a potential undesirable result that could potentially be used to confirm the adequacy of the minimum threshold methodology. Domestic wells are generally shallower than agricultural and m unicipal wells and thus more sensitive to undesirable effects such as wells going dry. Additionally, the loss of a domestic well usually results in a loss of water for consumption, cooking, and sanitary purposes, which can often have substantial impacts on the users of the water and can be financially difficult for the well owner to replace. The 10th percentile domestic well depth (i.e., the depth of the top 10 th percent most shallow well) was exam ined within a radius around the monitoring well representative of local conditions. A radius of three miles arou nd each representative monitoring well was used to identify the 10th percentile domestic well construction depth. For representative monitoring well 03N07E21L003, a 2-mile radius was used due to variations in groundwater levels due to its
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 8 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
proximity to the Mokelumne River. The 3-mile radius of each representative monitoring well (including the 2-mile radius of monitoring well 03N07E21L003), in cludes an average of 400 domestic wells each, collectively capturing approximately 76 percent of the domestic wells in the Subbasin. In cases where the 10th percentile domestic well depth was shallower than the historical drought low with the buffer, that value was developed as the minimum threshold to prevent undesirable results associated with dewatering wells in the Subbasin.
Domestic well data were retrieved from the Online System for Well Completion Reports (OSWCR) database, which is sparsely populated with information on total casing depth, screening intervals, and the age of the well. The 10
th percentile well depth was chosen due to the unc ertainty in the database and to account for the fact that domestic wells may have been drilled to a very shallow depth prior to the current well drilling standards enforced by local jurisdictions and/or have reached the end of their lifecycle. The 10th percentile domestic well depth for groundwater levels is protective of approximately 90 percent of the domestic wells in the OSWCR dataset and is used as a criterion for determining if a decline in groundwater levels is significant and unreasonable under SGMA. In municipalities with ordinances requiring the use of City water (water provided by the City ’s municipal wells), the 10th percentile municipal well depth is used in place of the 10th percentile domestic well depth criteria. Further more, removal of the dry water year designation from the definition of identification of undesirable results ensures that groundwater levels will not decline below the established minimum thresholds (See Technical Memorandum No. 1 – Undesirable Result Definition and Projects and Management Actions).
Potential Corrective Action 1(e)-1: Describe how they [the GSAs] 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.
Initial Review Provided by DWR
The Letter states “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.”
As a Potential Corrective Action, the following is suggested: “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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 9 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
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.”
Supplemental Information in Response to DWR Letter
Addressing Drinking Water Impacts
Refer to “Response to DWR Deficiency 1(a) and 1( b)” technical memorandum for discussion regarding removal of the water-year type requirement from the definition of an undesirable result for the chronic lowering of groundwater levels minimum threshold. As noted in this TM, the revised definition of an undesirable result for the chronic lowering of gr oundwater levels is when at least 25 percent of representative monitoring wells used to monitor groundwater levels (5 of 20 representative monitoring wells in the Subbasin) fall below their minimum level thresholds for two consecutive years.
The Eastern San Joaquin GSP contains 23 projects, where additional projects that support SGMA objectives have been identified since GSP adoption and submitta l. Refer to “Response to DWR Deficiency 1(a) and 1(b)” technical memorandum for the latest project information and how the projects will mitigate overdraft conditions. The majority of projects in the GSP include groundwater recharge utilizing existing and pending surface water rights, which will elevate groundwater levels within the project benefitting areas throughout the Subbasin.
The basis for design and selection of the sustainable management criteria (SMCs) is the lowest drought- related groundwater conditions ob served. The GWA and GSAs focused the GSP goals on the long-term sustainability of the Subbasin and implementation of projects that would help all beneficial users to have a reliable and resilient water supply, even in time of drought, and provide the ability to respond to climate change. The GWA and GSAs are supportive of ongoing agricultural, urban, and industrial water conservation efforts and to achieving the highest levels of water use efficiency technically achievable. It should be noted that water conservation programs have been successful in reducing urban and agricultural water demands such that those demands have become “hardened” and are less able to be reduced in time of drought without real impacts to the quality of life or economy. GSP projects and management actions are to reduce overdraft, and are designed to prov ide sustainable supplies through a dr ought without severe impacts to quality of life or the economy.
The GSP was not targeted toward emergency responses to drought or the short- term impacts associated with drought since this is the focus of the County Office of Emergency Services (OES) and a requirement for the water purveyors. In addition, the prevailing urban water management plans (UWMPs) and agricultural water management plans (AWMPs) identify water co nservation goals and demand reduction targets, including water shortage contingency plans, and the GWA and GSAs are supportive of those plans (and the drought contingency responses) and will encourage the lead agencies for those plans to implement actions and programs consistent with local and state requirements. The GWA will work to better coordinate with
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 10 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
the OES and urban purveyors to support emergenc y drought response efforts. The GWA and GSP development has included representatives from the urban suppliers and will continue to seek opportunities to engage with OES, the urban purveyors and to work to identify mutual goals, objectives and project opportunities.
With the removal of the water-year type requirement from the definition of an undesirable result for the chronic lowering of groundwater levels minimum threshold, established minimum thresholds will not allow for continued lowering of groundwater levels that will likely most severely impact shallow domestic well users. As noted in the prior explan ation, the depth of shallow domestic wells and production wells was considered in establishing the numerical minimum thresholds at the representa tive monitoring sites, thereby considering the depths of and potential impacts to drinking water users relying on groundwater. If drinking water impacts are observed during GSP impl ementation as a result of the established minimum thresholds, the ESJGWA will evaluate the need to revise the minimum thresh old methodology and/or implement additional projects or management actions to mitigate such impacts (as described in the “Response to DWR Deficiency 1(a) and 1(b)” tech nical memorandum). The GWA and GSAs will evaluate other programs as part of the adaptive manage ment strategy, and annual program evaluation and reporting. Neither SGMA nor the California Water Co de include requirements to mitigate for small and domestic systems or to include drought contingency pl ans in a GSP as this is the responsibility of other agencies or members of a GSA/GWA. If there is a statutory requirement included in the SGMA legislation at a future date, the GWA and GSAs will evaluate their programs and consider a well mitigation program.
In the meantime, the following management actions will be included:
1. Outreach to domestic well owners and small water systems. This will include information related to forecasted water levels with and without projects to inform subsequent investments decisions for well improvement and replacement.
2. Production and distribution of current and fo recasted groundwater level information to be provided to well permit applicants to inform the permitting process.
3. Review of well standards to evaluate opportunities to establish standards to better reflect current and forecasted groundwater level conditions.
4. The GWA and GSAs will actively promote small systems interties and/or consolidation of their systems to achieve supply reliability.
The future five-year update to the GSP will more closely evaluate and include information on UWMP water shortage contingency plans, and the GWA will coordi nate with the County OES to support emergency drought responses and plans.
The GSAs recognize that domestic wells may be impacted by declining groundwater levels, as well as other factors, including but not limited to, end of useful life. The GSAs intentionally set the minimum thresholds in the GSP to avoid domestic well failures due to declining groundwater levels. However, the GSAs recognize the need for a back-up process to mi tigate the impact of GSP managemen t on domestic well failures, if
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 11 Woodard & Curran, Inc.
TM2 - ESJ GSP Deficiency 1(d) and (e) Response_24Jun2022 June 2022
necessary. As part of the five-year update to the GSP, the GSAs, through the GWA, will identify additional management actions that can be implemented to address this situation, including considering development of a domestic well mitigation policy and program (“DWMP”).
REFERENCES
San Joaquin County Groundwater Basin Authorit y (Eastern San Joaquin County GBA). (2014). Eastern San Joaquin Integrated Regional Water Management Plan Update.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ATTACHMENT 1 – DWR Consultation Initiation Letter
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
November 18, 2021
Kris Balaji, PMP, P.E.
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 i nitiates
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. T he 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
determina
tion. 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 GSA s 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 GSA s should also provide a companion document with track ed changes of modifications made to address deficiencies. The GSA s 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 GSA s 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 GSA s 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
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 pot ential 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 h eading 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 G roundwater 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
qualitat
ive 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 GSA s, 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 e valuate 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 dr y water -year type s 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B 1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
• Chronic l
owering 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, t he 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 non- dry 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 classifications 15 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Department s
taff also find this methodology inconsistent with other portions of the GSP .
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 th e 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 GSA s 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 e limination of long -term overdraft conditions in the Subbasin. H owever, the GSP does not sufficient ly detail how projects and management actions, in conjunction with the proposed chronic lowering of groundwater levels sustainable management criteria, will o ffset 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 subsidence
19 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.2 1.3
1.4 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 T he 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 GS P states allows for operational flexibility .22 These minimum threshold values generally allow groundwater levels to decline below historic lows; minimum thresholds defined us ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.1 2
2.2 2.3
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 p rojects 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 GSA s 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 tota l 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 wit h a definition of undesirable result s 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 th eir 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.4 2.5
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
include an al
lowance 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 GSA s 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 achiev ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Potential Deficiency 2. The GSP does not provide enough information to support the use of the chronic lowering of g roundwater 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. H owever, 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 H owever, the GSP does not identify specific
infrastructure locations, particularly those associated with public saf ety, 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 s ubsidence, 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.1 3.2
3.3 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 driv ing 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, t he GSP is unclear on whether the conditions required to identify an undesirable result for chroni c 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 subsidence
34 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.4 3.5
3.6 3.7
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 suffic ient 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 preventati ve 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 1 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
TECHNICAL MEMORANDUM NO. 3 - Groundwater Quality
Degradation in Areas where further Groundwater Level Decline is Allowed
TO: Paul Gosselin, California Department of Water Resources Deputy Director CC: Kris Balaji, on behalf of the Eastern San Joaquin Groundwater Authority PREPARED BY: Matt Zidar, San Joaquin County Public Works, Water Resources Division Leslie Dumas and Natalie Cochran/Woodard & Curran
DATE: June 24, 2022
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s November 18, 2021 Consultation Initiation Letter - Response to DWR Deficiency 1(f) and Corrective Actions
The Eastern San Joaquin Groundwater Authority (ESJGWA) received a Consultation Initiation Letter (Letter) on November 18, 2021 (Attachment 1), from the Calif ornia Department of Water Resources (DWR). The Letter identified two potential deficiencies with the Eastern San Joaquin Groundwater Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) which may preclude DWR’s approval, as well as potential corrective actions to address each potential deficiency. The Letter thus initiated consultation between DWR, the Plan Manager, and the Subbasin’s groundwater sustainability agencies (GSAs) regarding the amount of time needed to address the potential deficiencies and corrective actions. A subsequent meeting with DWR was held on April 4, 2022 to discuss the Subbasin’s proposed approach to addressing the identified deficiencies.
The analysis presented in this memorandum was completed in resp onse to the Letter, based on direction provided by the ESJGWA, the Subbasin GSAs and DWR. It is intended to supplement the Eastern San Joaquin GSP that was submitted in January 2020 and fill potential gaps identified in the Letter provided by DWR.
Deficiency 1, as described in the DWR November 18, 2021 letter, is summarized as follows:
Potential Deficiency 1: The GSP lack s sufficient justification for determining that undesirable results for chronic lowering of groundwater levels, subsidence, and depletion of intercon nected 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.
The letter then went on to identify six potential corrective actions that could address this deficiency. This Technical Memorandum (TM) was prepared to address th e deficiency as described in Potential Correction Actions 1(f), which states the following:
“1(f) The GSP should be revised to explain how the GSAs will assess groundwa ter quality degradation in areas where further groundwater level decline, below historic lows, is allowed via the minimum thresholds. The GSAs should further describe ho w 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 coor dinate with water quality regulatory agencies and
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 2 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
programs in the Subbasin to understand and develop a process for determining if continued lowering of groundwater levels is resu lting in degraded water quality in the Subbasin during GSP implementation.”
The following subsections provide a response to each of the Potential Corrective Action 1(f) subparts listed above, and include a discussion with supplemental information, analysis, justification, and data needed to support the GSP and to address each issue identified.
Potential Corrective Action 1(f)-1: 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.
Initial Review Provided by DWR
The Letter states the GSAs “…have not explained how those groundwater level declines [allowed for by the GSP’s minimum thresholds] 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.”
As a Potential Corrective Action, the following is suggested: “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.”
Proposed Supplemental Information in Response to DWR Letter Explanation of Groundwater Level Declines and Degradation of Water Quality The only clear correlation between gr oundwater levels and water quality impairment from constituents of concern are related to the regional migration of poor-quality water from under the Delta to the groundwater pumping trough that is east of the City of Stockton. A gradient fr om the Delta toward the east causes the migration of poor-quality water into the Subbasin’s principal aquifers which can be exacerbated by increased pumping east of the Delta. U.S. Geologic Survey (USGS) data and prior studies suggest that high chloride groundwater is the result of the eastern movement of bracki sh San Joaquin Delta water and the upward movement of saline water associated with older marine deposits underlying freshwater aquifer units (Izbicki, 2006). Chloride and total dissolved solids (TDS ) have been the indicato r constituents for this potential degradation mechanism.
Other than for the movement of poor-quality saline groundwater from the Delta eastward as a result changes in groundwater gradients (whether occurring naturally, induced by groundwater pumping, and/or as a result of some other hydrologically-related pa rameter), there is no simple correlation between groundwater levels and groundwater quality (as characterized by a large number of naturally-occurring constituents such as manganese, arsenic, boron, and manmade constituents such as 1,2,3-TCP and PFOS.
Numerical modeling is one method of evaluating the hydraulic conditions which could cause migration and mixing of poor-quality water and the resultant degradation in groundwater quality; however, with the exception of simulating project-specific impacts, simulating long-term basin management would be difficult
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 3 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
and speculative given the large number of potential constituents of concern and possible sources of those constituents.
This potential for regional migration of saline wa ters was one of the reasons for developing prior groundwater management plans and the Integrated Conjunctive Use Pr ogram, and for implementing related Project Management Actions (PMAs) over the past 20 years. Projects implemented to date include projects to reduce groundwater pumping by providin g treated surface water in- lieu of groundwater use, such as the City of Stockton’s Delta Diversion Pr oject, which diverts Delta water for treatment and distribution in lieu of groundwater supplies. The Stoc kton East Water District (SEWD) Dr. Joe Waidhofer Water Treatment Plant also treats and purveys surface water to urban contractors, including the County of San Joaquin, City of Stockton, and California Water Service. These two in-lieu projects have helped decrease groundwater pumping and have allowed for recovery of groundwater levels on the order of 14 to 20 feet.
This has reduced, but not eliminated, the eastern migration of poor-quality water from the Delta into the Subbasin by reducing the groundwater hydraulic gradient eastward from the Delta.
Implementation of the other PMAs included in the Eastern San Joaquin (ESJ) Groundwater Sustainability Plan (GSP) is intended to raise groundwater levels or, at minimum, keep levels in the operating zone defined as the elevations between the Measurable Objective (MO) and the Minimum Threshold (MT) established to avoid undesirable results. These sustainable management criteria were set specifically to help prevent the further migration of saline water. The relationsh ip between the MOs and MT s for groundwater levels considered water quality and the afore-described saline water migrat ion because there was a known potential and causality, even if no clear correlations.
There are dedicated monitoring wells that have been constructed in the past 20 years and a production well network which together serve as sent inels to track chloride and TDS as indicators of the saline water and potential migration (please see ESJ GSP Figure 2-58, pg. 2-84) and to moni tor the sustainability indicators for this management problem. These wells are also part of the ESJ GS P representative monitoring well network.
California Code of Regulations (CCR) Title 22 establis hes water quality standards for drinking water contaminants. A secondary MCL (SMCL) is defined for a variety of parameters, including chloride and TDS.
Secondary MCLs are based on user acceptability of th e quality of drinking water, as opposed to being established to protect human heal th. For the purposes of this GSP, comparing chloride and TDS concentrations to their respective SMCLs is the basis for monitoring the above-described groundwater quality concerns in the Eastern San Joaquin Subbasin. [should reference data for the water in or under the Delta that is of concern – do levels of chloride and/or TDS in these waters exceed SMCLs? i.e. do they pose a risk of causing exceedances in adjacent groundwater?] Nexus Between GWL and WQ
Except for the potential for regional migration of saline water, there is no evidence or historical data to indicate that there is relationship between lowering of groundwater levels and groundwater quality degradation. We have not observed, nor can we anti cipate, any causal connection between groundwater management actions that can be undertaken by GSAs, and lowering gr oundwater levels that would result in degradation associated with other constituents of concern.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 4 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
There are, however, potential mechanisms for lowering groundwater levels to influence water quality. These include:
Falling groundwater levels which may cause migrat ion of already-contaminated groundwater from natural sources, nonpoint sources (salt, nitrate), or a plume from a point source where a potential responsible party is known.
Rising groundwater levels creating changes in oxidation potential and mobilization of arsenic. Rising groundwater levels from recharge operations or reduce pumping that could mobilize nitrates or salts in the vadose zone.
The GSP reviews water quality issues regarding nitrates, arsenic, and salts, referencing Regional Water Quality Control Board (RWQCB) programs under the Central Valley Water Quality Control Plan, and those of the State Water Resources Contro l Board, including the Irrigated Lands Regulatory Program and the CVSALTS initiative, generally describin g these programs and relationship to these efforts. The intent is to acknowledge those jurisdictions and authorities, crea te awareness of the areas of responsibility for management and regulation, and identify where there are known water quality issues and impairments to beneficial use being addressed through those auth orities. The GSP acknow ledges the Central Valley Regional Water Quality Control Board (RWQCB)/ State Water Resources Control Board (SWRCB) responsibilities, including those of the Division of Drinking Water, and documents these programs and how they influence the GSAs PMAs and groundwater management in the region to be consistent and respectful of the authorities and programs of these related agencies . This includes local Environmental Health Department authorities to protect drinking water quality, health, and safety.
There may be a relationship between PMAs to be implemented by GSAs that merit review at the time such projects are proposed and subject to California Environmental Quality Act (CEQA), and if potential impacts are identified during scoping and th e input of the responsible or trus tee agencies. Any PMA that could result in violation of MCLs as a threshold of significance would require mitigation and monitoring to ensure there are no negative effects. For example, groundwater recharge has been observed to result in short term increases in nitrogen concentration in groundwater due to the flushing of nitrate from the soil and/or vadose zone to the water table. This known potential negative effect would require evaluation during project development and ongoing monitoring and mitigation during operation. The rising water table associated with a recharge project could also in tersect with nitrogen entrained in the pore space in the vadose zone and mobilizing this constituent. Both effects have been observed to be short term in nature as more clean water is recharged over time and typically improves ambient water quality. Regardless, impacts would be evaluated and mitigated as required under CEQA.
Varying groundwater levels may al so change geochemical conditions and result in oxidation and mobilization of some elements. This is one mechanism for mobilizing arsenic; however, there is not enough data to evaluate causal relationship or correlations with groundwater levels at this time. The GSP notes the monitoring well and drinking water well monitoring and reporting of arsenic levels.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 5 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
Potential Corrective Action 1(f)-2: Describe how they will coordinate with the appropriate groundwater users, including drinking water, environmental, and irrigation users as identified in the GSP
Initial Review Provided by DWR
The Letter states “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 to tal dissolved solids, it is clear that the GSAs did not consider, or at least did not document, the potentia l for degradation to occur due to further lowering of groundwater levels beyond the historic low.”
As a Potential Corrective Action, the following is suggested: “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.”
Supplemental Information in Response to DWR Letter
GSAs Assessment of Groundwater Quality Degradation
The ESJ GSP and PMAs are designed to prevent further groundwater level declines below the historic level and MTs established. The representative water quality monitoring well network in the area where lowering of groundwater levels may lead to degradation of water quality, along with tr acking of other regional monitoring by the RWQCB, SWRCB and local water purveyors, will allow the GSAs to observe water quality conditions and identify when groundwater level MTs are exceeded to determine if water quality exceeds the SMCLs at the MT for the constituents of concern referenced in the GSP. If groundwater level MTs and groundwater quality SMCLs as MTs are exceeded, the GWA will convene a working group consisting of GSAs, regulators and local water purveyors to conduct and publish an assessment of the effect of groundwater management activities on the documented exceedance and propose timely corrective actions to manage groundwater diffe rently, if needed, to avoid exacerbating the exceedance and to address the resultant undesirable results.
Through the ESJGWA, the GSAs will collaborate and share data with other programs monitoring water quality data to observe both ambient and regulated conditions.
Coordination with Groundwater Users
GSP implementation by th e ESJGWA includes stakeholder coordi nation, outreach and engagement of groundwater users, and seeks to involve representatives of the different beneficial uses and users, including non-governmental organizations. The ESJGWA mainta ins a web site, is working to implement a data management system to provide transparent access to available ground water level and quality data, and produces and distributes the requir ed Annual Report which is a primary tool for communicating basin conditions and progress in achieving sustainability. The Annual Report includes documentation of efforts to coordinate with the other monito ring and regulatory programs to br ing data and information into the
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 6 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
ESJGWA discussions and build awareness of how groundwater levels and quality may be managed together to achieve sustainability.
The Subbasin’s Technical Advisory Committee will be used to review monitoring data from the GSP programs, and to integrate information from other monitoring programs into the Annual Report to identify where constituents of concern are degrading water quality and will seek to define if there is a relationship between groundwater levels and impacts to beneficial use.
Potential Corrective Action 1(f)-3: 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 Initial Review Provided by DWR
The Letter states “While Department staff are not aware of evidence sufficient to conclu de that the GSAs acted unreasonably by focusing on to tal dissolved solids, it is clear that the GSAs did not consider, or at least did not document, the potentia l for degradation to occur due to further lowering of groundwater levels beyond the historic lows.”
As a Potential Corrective Action, the following is suggested: “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.” Supplemental Information in Response to DWR Letter
Coordination with Water Quality Regulatory Agencies and Programs The primary state authority for protecting water quality under the Porter Cologne Water Act is the SWRCB and RWQCB via the Water Quality Control Plans (also known as Basin Plans) which define the beneficial uses of water (including groundwater), set water quality numeric and narrative objectives, establish priorities, and implement programs to manage both point and non- point sources of contamination. The Water Boards coordinate with the other state programs including, the Department of Pesticide Regulation.
Section 3.2.3.1.1 of the GSP discusses the Irrigated Lands Regulatory Program (ILRP) and Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS), two existing regulatory programs for the monitoring and regulation of nitrate and salts in the Central Valley. Under the ILRP, the San Joaquin County & Delta Water Quality Coalition (Coalition) is required to test and potentially mitigate for nitrate in domestic wells. The Coalition has 40 trend monitoring wells throughout San Joaquin County that are sampled yearly to determine the nitrate levels in the groundwater. They also hold grower meetings and conduct outreach to growers on best management practices that are protective of water quality for both surface water and groundwater. The Coalition completed its Groundwater Assessment Report in 2015 that identified areas that were highly susceptible to nitrate from agriculture leaching into groundwater (High Vulnerability Areas). The Coalition also analyzes monitoring data and grower-prepared nitrate
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 7 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
management plan information to determine if the growers follow the requirements of the Irrigated Lands Regulatory Program. The Coalition then reports this analysis with required information to the Central Valley Regional Water Quality Board on an annual basis.
Additionally, the 2017 Salt and Nitrate Control Program, developed by CV-SALTS, identifies long-term nitrate management requirements (CVRWQCB, 2016). The Eastern San Joaquin Basin is Priority 2 Basin under the nitrate control program. The CV-SALTS Prioritization and Optimization (P&O) Study is a long- term effort to develop, plan and implement solutions for managing and controlling salt accumulation in the Valley.
In May 2018, because of CV-SALTS program efforts, a new Salt and Nitrate Management Plan (SNMP) was approved by the Central Valley Regional Water Quality Control Board as Amendments to the Basin Plans for the Sacramento River, San Joaquin River Basin and the Tulare Lake Basin. The State Water Resources Control Board then directed targeted revisions to the Amendments adopted by the Central Valley Water Board. The following Proposed Revisions were approved with an effective date of November 10, 2021. Salt and Nitrate Control Program Basin Plan Amendments – Proposed Revisions (2021) Salt and Nitrate Control Program – Basin Plan Amendment (2019) The State Water Resources Control Board Division of Drinking Water and local health agencies monitor drinking water quality to protect public health and safety. Their programs and the proposed ESJ monitoring should share data to better diagnose and treat potential or known water quality impairments.
ESJGWA and GSA Project Management Actions
The ESJ GSP also proposes the following program management actions for the Subbasin GSAs to be coordinated through the ESJGWA. These include:
1. Regular Process for coordination
a. The ESJGWA will hold an annual “groundwater water quality state of the basin” meeting or workshop in January and invite the members of the Coalitions to present the results of the monitoring program.
b. The ESJ Technical Advisory Committ ee (TAC) will invite participation and ex officio representation from the RWQCB staff to receive regular information regarding ILRP, CV-SALTS and any planned updates or amendments to the San Joaquin Water Quality Control Plan.
2. Monitoring
a. The ESJGWA will seek to develop monitoring and data sharing agreements with the Coalition. b. ESJGWA staff will work with the local Enviro nmental Health Division and SWRCB Division of Drinking to identify drinking water wells which are nearing or have exceeded MCLs or SMCLs, noting the location, number of wells and the constituents of concern.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 8 Woodard & Curran, Inc.
TM3 - ESJ GSP Deficiency 1(f) Response_24Jun22 June 2022
3. Data Management. Where possible, the ESJGWA will include the water quality data collected via other monitoring networks in their annual assessments, and will use this information to further evaluate trends and any correlations between groundwater levels, the groundwater level MTs, and observed water quality conditions.
4. Annual Report. Beyond the reporting of data from the GSP groundwater level and water quality monitoring network, the ESJ Annual Report will include expanded groundwater quality discussion to document:
a. The annual results of the Coalitions monitoring program b. Known impairments identified by the RWQCB pursuant to the Water Quality Control Plans c. Wells and locations where MCLs have been exceeded as identified by the SWRCB Division of Drinking Water, consumer confidence reports, or the local Environmental Health Department
REFERENCES
Central Valley Regional Water Quality Control Board. 2022. Irrigated Lands Regulatory Program, Program Brochure. As viewed at
https://www.waterboards.ca.gov/centralvalley/water_issues/irrigated_lands/outreach_brochure.pdf.
Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS). 2016. Central Valley Region Salt and Nitrate Management Plan, Final Document for Central Valley Water Board Consideration.
December. As viewed at https://www.cvsalinity.org/resources/basin-planning/ CV-SALTS. 2022. New Salt Control Program for the Central Valley. January. As viewed at https://cvsalinity- my.sharepoint.com/personal/cv-
salts_cvsalinity_org/_layouts/15/onedrive.aspx?id=%2Fpersonal%2Fcv%2Dsalts%5Fcvsalinity%5Forg%2FD ocuments%2FWebsite%5FResources%2FGeneral%20Information%20Materials%2FSalt%20Control%20Fact %20Sheet%201%2D13%2D21%2Epdf&parent=%2Fpersonal%2Fcv%2Dsalts%5Fcvsalinity%5Forg%2FDocu ments%2FWebsite%5FResources%2FGeneral%20Information%20Materials&ga=1.
CV-SALTS. 2022. Salt Control Program and P&O Study Update. February. As viewed at https://cvsalinity- my.sharepoint.com/personal/cv-
salts_cvsalinity_org/Documents/Website_Resources/General%20Information%20Materials/Salt%20Control %20Program%20Brief%20final%203-15-22.pdf?ga=1.
Izbicki, John A., Loren F. Metzger, Kelly R. McPherson, Rhett R. Everett, and George L. Bennett V. 2006.
Sources of High-Chloride Water to Wells, Eastern San Joaquin Ground-Water Subbasin, California. U.S.
Geological Survey Open File Report 2006-1309. As viewed at https://pubs.usgs.gov/of/2006/1309/pdf/ofr2006-1309.pdf
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 1 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
TECHNICAL MEMORANDUM NO. 4 – LAND SUBSIDENCE
TO: Paul Gosselin, California Department of Water Resources Deputy Director PREPARED BY: Kris Balaji, on behalf of the Eastern San Joaquin Groundwater Authority DATE: June 24, 2022
RE: Eastern San Joaquin Groundwater Authority Response to DWR’s November 18, 2021 Consultation Initiation Letter – Response to Potential Deficiency No. 2 and Corrective Actions
1. Introduction
The Eastern San Joaquin Groundwater Authority (ESJGWA) received a Consultation Initiation Letter (Letter) on November 18, 2021 (Attachment 1), from the California Department of Water Resources (DWR). The Letter identified two potential deficiencies with the Eastern San Joaquin Groundwater Subbasin (Subbasin) Groundwater Sustainability Plan (GSP) which may preclude DWR’s approval, as well as potential corrective actions to address each potential deficiency. The Letter thus initiated consultation between DWR, the Plan Manager, and the Subbasin’s groundwater sustainability agencies (GSAs) regarding the amount of time needed to address the potential deficiencies and corrective actions. A subsequent meeting with DWR was held on April 4, 2022 to discuss the Subbasin’s proposed approach to addressing the identified deficiencies. The analysis presented in this memorandum was completed in response to the Letter, based on direction provided by the ESJGWA, the Subbasin GSAs and DWR. It is intended to supplement the Eastern San Joaquin GSP that was submitted in January 2020 and fill potential gaps identified in the Letter provided by DWR.
The following sections provide a response to the Potential Corrective Actions identified under Potential Deficiency 2.
2. Potential Deficiency 2
Potential Deficiency 2. The GSP does not provide enough information to support the use of the chronic lowering of groundwater levels sustainable management criteria and representative monitoring network as a proxy for land subsidence
Under Potential Deficiency 2, DWR identified deficiencies rela ted to the use of the chronic lowering of groundwater levels sustainable management criteria and representative monitoring network as a proxy for land subsidence.
Specifically, DWR requests additional information demonstr ating significant correlation between groundwater levels and land subsidence to demonstrate that groundwater level minimum thresholds represent a reasonable proxy for avoiding land subsidence undesirable results. The GSAs must additionally demonstrate how the monitoring network is adequate to identify undesirable results for land subsidence.
To address findings identified under Potential Deficiency 2, DWR has put forward Potential Corrective Action 2 for GSA consideration. Potential Corrective Action 2 contains three subparts, which are summarized below. Potential Corrective Action 2-1: Identify the total extent and rates of subsidence that critical infrastructure in the Subbasin can tolerate during GSP implementation. Potential Corrective Action 2-2: Document a significant correlation between groundwater levels and specific amounts or rates of land subsidence. Account for potential subsidence related to groundwater level declines below historic lows and further declines that would exceed minimum threshold levels. Demonstrate that
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 2 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
groundwater level declines allowed during GSP implemen tation are preventative of the rates and extent of land subsidence.
Potential Corrective Action 2-3: Explain how the groundwater level representative monitoring network is sufficient to detect significant and unreasonable rates or extents of land subsidence that may substantially interfere with land uses.
The following subsections provide a response to each of t he Potential Corrective Action subparts listed above, and include a discussion with supplemental information, analysis, justification, and data needed to support the GSP and address each issue identified.
Potential Corrective Action 2-1: Identify the total extent and rates of subsidence that critical infrastructure in the Subbasin can tolerate during GSP implementation Initial Review Provided by DWR
The Letter states the GSP “does not adequately identify or define minimum thresholds and undesirable results for land subsidence… [and] 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”. The Letter further clarifies that, “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.”
As a Potential Corrective Action, the following is suggested: “The GSA 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.” Supplemental Information in Response to DWR Letter
Identification of Critical Infrastructure
The GSP describes an undesirable result for land subsidence in the Eastern San Joaquin Subbasin as occurring if land subsidence substantially interferes with beneficial uses of groundwater and infrastructure within the Subbasin over the planning and implementation horizon of the GSP. In coordi nation with the San Joaquin County Department of Public Works and the San Joaquin County Office of Emergency Services, the following infrastructure types have been identified as those potentially at risk for interference from land subsidence, if it were to occur in the Subbasin. Please note that, as discussed with DWR during the April 4
th meeting, due to the sensitive nature of the critical infrastructure, specific infrastructure are not named and, rather, only the principal categories of these types of infrastructure are discussed below.
Critical infrastructure at risk for subsidence impacts:
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 facilities
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 3 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
The Subbasin is served by an extensive road network, including major interstate highways. The San Joaquin County Department of Public Works maintains the County’s 120-mile network of underground facilities, over 1,600 miles of roadway, 265 bridges, and 364 minor structures. In additi on, San Joaquin County supports air service, a deep water port, transcontinental rail, and commuter trains. Major roadways located within the Subbasin boundary include Interstate 5 (I-5) and multiple State Routes (4, 12, 26, 88, 99, 120). Major bridges in the Subbasin serve both automobile and railroad transport. Major bridges in the subbasin include the San Joaquin River Bridge, Littlejohns Creek Bridge, Mormon Slough Bridge, and the Union Pacific Mossdale Bridge East.
Service buildings within the Subbasin include fire stations, hospitals, jails and correction facilities, police stations, and wastewater plants. The County also maintains 30 water systems with 52 wells, 3 sewage treatment plants, 9 sewage pumping stations, 68 storm drain pumping stations, and over 300 miles of levees and flood channels. In general, major pipelines that run through the County are in areas south of Lodi and southw est of Tracy along the foothills (outside of the Subbasin boundary).
In addition to identi fying critical infrastructure at risk for subsidence impacts, the ESJGWA has worked with OES to identify the total subsidence load that critical infrastructure in the Subbasin can tolerate during GSP implementation, and what would be considered an undesirable result. Through input from OES, the critical infrastructure in the Subbasin can generally tolerate a significant amount of uniform se ttlement 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. However, it is worth noting that it is less common for subsidence to cause significant local differential sediment. In addition, the San Joaquin County 2017 Local Hazard Mitigation Plan identifies land subsidence as a potential cause for levee breakage; however, the hazard of subsidence is ranked “not likely” to occur.
Potential Corrective Action 2-2: Document a significant correlation between groundwater levels and specific amounts or rates of land subsidence. Account for potential subsidence related to groundwater level declines below historic lows and further declines that would exceed minimum threshold levels. Demonstrate that groundwater level declines allowed during GSP implementation are preventative of the rates and extent of land subsidence.
Initial Review Provided by DWR
The second part of this Potential Corrective Action see ks additional information to document a significant correlation between groundwater levels and land subsidence. The Letter states the GSP “fails to provide adequate evidence to evaluate further [the correlation between groundwater levels and land subsidence], specifically concerning potential subsidence caused by groundwater levels falling below historic lows, as would be allowed by the groundwater level minimum threshold set in the GSP. The Letter further states that 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”, “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”, and “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.” As a Potential Corrective Action, the following is suggested: “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
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 4 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
sensed data provided by the Department, extensometers, or GPS stations) until such time that the GSAs can establish a correlation.”
Supplemental Information in Response to DWR Letter
Areas Potentially At-Risk for Subsidence
As discussed in the GSP, despite long-term declining groundwater levels in the Subbasin, there are no historical records of impacts from land subsidence in the Eastern San Joaquin Subbasin. Figure 1 shows regional subsidence produced from TRE Altamira Interferometric Synthetic Aperture Radar (InSAR) data, provided by DWR for SGMA application. This figure illustrates that subsidence has historically been minimal in the Subbasin and surrounding areas (ranging from -0.1 to 0.1 feet of vertical displacement annually). This corresponds with what San Joaquin County Public Works and San Joaquin County Office of Emergency Services staff have observed anecdotally, that the Subbasin has not historically experienced issues with land subsidence.
In the Subbasin, there are two potential mechanisms that could potentially contribute to inelastic land subsidence: 1) groundwater extraction resulting in dewatering and collapse of compressible clays in the subsurface, 2) and the oxidation of peaty soils.
Mechanism 1: Subsidence Caused by Dewatering and Collapse of Compressible Clays The first mechanism for inelastic land subsidence involves the presence of compressible clays and strata in the subsurface, which are not known to be common in the Eastern San Joaquin Subbasin. The Corcoran Clay is one type of subsurface material that is potentially predisposed to compression, especially in the San Joaquin Valley. While dominant in basins to the south, the extent of Corcoran Clay within the Eastern San Joaquin Subbasin is limited to the extreme southwest corner of the Subbasin, near the City of Manteca. Figure 2 shows the extent of Corcoran Clay within the Subbasin. This figure also includes hydrographs for two monitoring wells located in this area, one in the Representative monitoring network for chronic lowering of groundwater levels, and one in the Broad monitoring network for chronic lowering of groundwater levels. In addition, there are two other Broad groundwater level monitoring network wells that fall within the Corcoran Clay boundary but are outside of the boundary of the available Corcoran Clay depth raster dataset. As shown in the hydrographs provided, historical water levels have remained relatively constant in this area and are well above the Corcoran Clay elevation.
Well 02S07E31N001M (shown as well “A” in Figure 1) is in the Representative monitoring network for chronic lowering of groundwater levels. This well is located in the South Delta Water Agency (SDWA) GSA and has a minimum threshold set at 1.5 feet mean sea level (ft MSL), which while below t he historical average, is still well above the Corcoran Clay elevation at that location (-176 ft MSL). The ESJGWA has ident ified a numeric trigger for groundwater levels at which subsidence would become a concern as -150 ft MSL in the portion of the Subbasin were Corcoran Clay is present.
This numeric trigger was selected based on available Corcoran Clay elevation data and is intended to capture the shallowest Corcoran Clay in the Subbasin.
The Corcoran Clay layer in the Subbasin is not anticipated to become dewatered if groundwater levels do not drop below the elevation at which Corcoran Clay is present. Because the minimum thresholds for groundwater levels in the portion of the Subbasin where Corcoran Clay is present are higher in the aquifer than the elevation of the Corcoran Clay, groundwater levels are not anticipated to drop below the elevation at which Corcoran Clay is present. Therefore, if groundwater levels are maintained above their minimum thresholds, the Corcoran Clay layer, which is lower in elevation, would not become dewatered and therefore would not become compressed. Thus, the chronic lowering of groundwater levels minimum threshold is protective against dewatering of Corcoran Clay in the Subbasin.
Figure 3 (GSP Hydrogeologic Cross-Section E-E’) shows the extent of Corcoran Clay in cross-section. As shown, the Corcoran Clay becomes interbedded with the sands and silt of the upper Turlock Lake Formation. Here, the clay is typically 20 to over 100 feet thick and is locally eroded and interfingered with coarser materials at its margin. It is not found in the central and northern portions of the Subbasin.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 5 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Mechanism 2: Subsidence Caused by the Oxidation of Peaty Soils The second mechanism for inelastic land subsidence in the Subbasin area, the oxidation of peaty soils, does not appear to be directly related to groundwater pumping in the Subbasin (the management mechanism for Subbasin sustainability). As shown in Figure 4, the organic basin soils are restricted to the lower Sacramento-San Joaquin River Delta (Delta) portion of the Subbasin. Peat, muck, and clay loam are terms commonly applied to soils in this group.
Figure 5 shows the distribution of present-day modeled subsidence rates due to the oxidation of peaty soils in the Delta region, which ranges from 0 to 1.84 centimeters per year.
There are numerous factors that contribute to peat oxidation-related subsidence. Generally, these include (1) shrinkage due to dewatering, (2) consolidation due to loss of buoyant force and loading, (3) wind and water erosion, (4) oxidation of soil organic matter, and (5) burning. According to findings presented in Present-day oxidative subsidence of organic soils and mitigation in the Sacramento-San Joaquin Delta, California, USA (Deverel et al., 2016), subsidence rates in the Sacramento-San Joaquin Delta are primarily related to soil organic matter content, and secondarily to water- and land-management practices that determine depth to groundwater. This paper identifies rice cultivation and permanently flooded wetlands as the primary mitigation tools. As noted by Deverel et. al., depth to groundwater on Delta subsided islands is controlled primarily by networks of drainage ditches that feed to island drainage pumping stations that, in turn, continuously discharge drainage water to Delta channels. Drainage ditches collect water that seeps from adjacent channels and deep percolation of applied irrigation water. There are few depth-to-groundwater measurements in Delta organic soils and, in general, groundwater levels have been maintained at about 0.8–1.2 meters below land surface as the result of drainage system operation. Deverel also notes that based on his experience in working in the organic soils throughout the Delta since the early 1980s, depth to groundwater has not changed substantially over time in most places and prior research indicates a lack of change in Delta groundwater levels since the late 1980s (Deverel et al. 2016).
Figure 6 shows annual groundwater pumping in the Subbasin for Water Year 2021 and indicates that minimal groundwater extraction occurs in this area of the Subbasin.
Supplemental Land Subsidence Monitoring
To further supplement the land subsidence data collection efforts put forward in the GSP, continuous global positioning system (CGPS) data, InSAR data, and ot her subsidence data have been, and will continue to be, evaluated annually by the ESJGWA in coordination with the planned use of chronic lowering of groundwater level minimum thresholds as a proxy for land subsidence. The GSAs will monitor these data sets to better understand and report actual subsidence that occurs (if any) as groundwater levels decline.
These data will be compiled and evaluated each year as part of the data assessment and production of the Annual Report, submitted to DWR each April 1. In addition, the ESJGWA will revisit the Hydrogeologic Conceptual Model (HCM) presented in the Subbasin’s GSP after DWR’s Airborne Electromagnetic (AEM) data become available. 1 At that time, the ESJGWA will adju st the representative monitoring network and methods as needed based on improved basin understanding to refine their methods for monitoring for inelastic land subsidence. This analysis and any subsequent revisions will be incorporated in the GSP five-year update.
In time, the ESJGWA will endeavor to identify a correlation between groundwater levels and subsidence, as suggested by DWR. Below is a description of land subsidence datasets currently available for ESJGWA use and analysis.
UNAVCO’s Plate Boundary Observatory Program – Reporting since 2004, the UNAVCO (formerly University Navigation Satellite Timing and Ranging or NAVSTAR Consortium) Plate Boundary Observatory network consists of a
1 DWR is conducting AEM surveys in California’s high- and medium-priority groundwater basins, where data collection is feasible, to assist local water managers as they implement the Sustainable Groundwater Management Act (SGMA) to manage groundwater for long term sustainability. AEM surveys began in the summer of 2021 and will continue over the next several years. Eastern San Joaquin Subbasin is included in DWR's Survey Area 6, which is expected to be surveyed April 3-23, 2022, per the Tentative AEM Survey Schedule released by DWR. By this schedule, AEM data for the Subbasin is tentatively expected to be available in the first quarter of 2023.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 6 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
network of about 1,100 CGPS and meteorology stations in the western United States to measure deformation resulting from the constant motion of the Pacific and North American tectonic plates in the western United States. Stations located within the Subbasin contain data from at least 2006 to current and include Station P309, located east of Linden, and Station P273, located west of Lodi. Other stations are also available in nearby Subbasins.
United States Geological Survey – The USGS report Land Subsidence along the Delta-Mendota Canal in the Northern Part of the San Joaquin Valley, California, 2003-10 (Sneed et al., 2013) presents land subsidence data in the southwestern portion of the Eastern San Joaquin Subbasin from 2007 to 2010. Data for about 100 square miles of the Subbasin were recorded using InSAR processing, a satellite-based remote sensing technique that can detect ground- surface deformation. Two InSAR techniques were used: conventional InSAR and persistent scatter (PS) InSAR. Both sources of data were collected from the Japanese Aerospace Exploration Agency’s Advanced Land Observing Satellite.
Other -– DWR has made two InSAR datasets available for SGMA application: TRE Altamira InSAR point and raster data and NASA JPL raster data. Vertical displacement approximations in both datasets are collected by the European Space Agency’s Sentinel-1A satellite. The two different datasets represent two di fferent processing results, one by TRE Altamira Inc. and one by NASA JPL. The TRE Altamira data have coverage between January 2015 and October 2020. Both annual and total raster datasets from TRE Altamira are available and represent interpolations of the vertical displacement point features. The NASA JPL processed dataset spans Spring of 2015 to Summer of 2017.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 7 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Note: This dataset represents measurements of vertical ground surface displacement in between spring 2015 and summer 2017 (TRE Altamira, 2019).
Figure 1. Subsidence (Annual Rate of Vertical Displacement)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 8 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Figure 2. Extent of Corcoran Clay in the Eastern San Joaquin Subbasin with Select Representative Well Hydrographs
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 9 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Figure 3. Hydrogeologic Cross-Section E-E’
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 10 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Figure 4. Soil Depositional Areas
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 11 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Source: Present-day oxidative subsidence of organic soils and mitigation in the Sacramento-San Joaquin Delta, California, USA (Deverel et. al, 2016)
Figure 5. Oxidative Subsidence Rates in the Sacramento- San Joaquin Delta
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 12 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Figure 6. Average Annual Groundwater Pumping (Water Year 2021)
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 13 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
Potential Corrective Action 2-3: Explain how the groundwater level representative monitoring network is sufficient to detect significant and unreasonable rates or extents of land subsidence that may substantially interfere with land uses.
Initial Review Provided by DWR
The third part of the Potential Corrective Action under Deficiency 2 seeks additional information on how the chronic lowering of groundwater levels representative monitoring network is sufficient to detect significant and unreasonable subsidence that may substantially interfere with land uses, specifically any identified infrastructure of concern. The Letter states 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.” In addition, the Letter states, “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.” As a Potential Corrective Action, the following is suggested: “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.” Supplemental Information in Response to DWR Letter
The decision to use the groundwater levels representative monitoring network as a proxy for land subsidence was based on the information discussed in the prior section of this document. The GSAs recognize that additional land subsidence data collection and monitoring in the Subbasin over the first few years of GSP implementation will be an important indicator in assessing if the groundwater levels representative monitoring network alone will be sufficient to evaluate potential movement towards significant and unreasonable impacts to infrastructure due to inelastic land subsidence, particularly given that the Subbasin has not historically experienced issues related to land subsidence.
For this reason, and in response to DWR’s suggestion to incorporate continued analysis of available InSAR data to cover areas with data gaps, the GSAs have committed to annual collection and evaluation of land subsidence data from publicly available sources, including CGPS, InSAR, and other data sources, for assessment with data collected from its representative monitoring network. Data will be evaluated annually, and if subsidence is apparent, projects and management actions in that area will be triggered. The ESJGWA will establish a trigger value of 0.25 feet (annual rate of vertical displacement) at which point an analysis will occur to determine if the subsidence is directly related to groundwater management, and if deemed so, additional projects and management actions are triggered.
The ESJGWA has also determined that, following receipt of the DWR’s AEM data, the GSAs will re-evaluate and update the representative monitoring network for land subsidence as part of GSP five-year update and in coordination with improvements and refinements to the GSP HCM through the use of the AEM survey data and new boring log data that becomes available.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Eastern San Joaquin Groundwater Authority 14 Woodard & Curran, Inc.
TM 4 - ESJ GSP Deficiency 2 Response_24Jun2022.docx June 2022
REFERENCES
Deverel, Steven J., Timothy Ingrum, and David Leighton (2016), Present-day oxidative subsidence of organic soils and mitigation in the Sacramento-San Joaquin Delta, California, USA. Hydrogeology Journal (2016) 24:569-586.
Sneed, Michelle, Justin T. Brandt, and Mike Solt (2013), Land Subsidence along the Delta-Mendota Canal in the Northern Part of the San Joaquin Valley, California, 2003-10. U.S. Geological Survey Scientific Investigations Report 2013-5142. As viewed at https://pubs.er.usgs.gov/publication/sir20135142.
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
ATTACHMENT 1 – DWR Consultation Initiation Letter
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
November 18, 2021
Kris Balaji, PMP, P.E.
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 i nitiates
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. T he 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
determina
tion. 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 GSA s 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 GSA s should also provide a companion document with track ed changes of modifications made to address deficiencies. The GSA s 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 GSA s 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 GSA s 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
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 pot ential 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 h eading 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 G roundwater 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
qualitat
ive 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 GSA s, 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 e valuate 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 dr y water -year type s 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B 1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
• Chronic l
owering 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, t he 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 non- dry 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 classifications 15 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.1 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Department s
taff also find this methodology inconsistent with other portions of the GSP .
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 th e 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 GSA s 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 e limination of long -term overdraft conditions in the Subbasin. H owever, the GSP does not sufficient ly detail how projects and management actions, in conjunction with the proposed chronic lowering of groundwater levels sustainable management criteria, will o ffset 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 subsidence
19 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
1.2 1.3
1.4 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 T he 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 GS P states allows for operational flexibility .22 These minimum threshold values generally allow groundwater levels to decline below historic lows; minimum thresholds defined us ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.1 2
2.2 2.3
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 p rojects 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 GSA s 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 tota l 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 wit h a definition of undesirable result s 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 th eir 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
2.4 2.5
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
include an al
lowance 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 GSA s 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 achiev ing 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
Potential Deficiency 2. The GSP does not provide enough information to support the use of the chronic lowering of g roundwater 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. H owever, 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 H owever, the GSP does not identify specific
infrastructure locations, particularly those associated with public saf ety, 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 s ubsidence, 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.1 3.2
3.3 DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 driv ing 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, t he GSP is unclear on whether the conditions required to identify an undesirable result for chroni c 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 subsidence
34 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).
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
3.4 3.5
3.6 3.7
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT
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 suffic ient 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 preventati ve 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.
DocuSign Envelope ID: 90098AF4-85B5-4D3D-9995-AF15E867F30B
DRAFT ATTACHMENT B
ATTACHMENT C
DRAFT