12.B Attachment 1 NCMA Annual Report 2023 2025-07-01 (Online Only) — Pismo Beach City Council, July 1, 2025 (part 1 of 3)

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Northern Cities Management Area Technical Group
Northern Cities Management Area
2024 Annual Monitoring Report
Prepared for
City of Arroyo Grande  City of Grover Beach 
Oceano Community Services District  City of Pismo Beach April 2025
Prepared by:

GSI Water Solutions, Inc.
800 Quintana Road, Suite 2C, Morro Bay, CA 93442

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Northern Cities Management Area
2024 Annual Monitoring Report
This report was prepared by the staff of GSI Water Solutions, Inc., in collaboration with GEI Consultants, Inc., under the supervision of professionals whose signatures appear below. The findings or professional opinions were prepared in accordance with generally accepted professional engineering and geologic practice.

Michael McAlpin, PG
Supervising Hydrogeologist
Project Manager
Dave O’Rourke, PG, CHG
Principal Hydrogeologist

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Contents
Executive Summary .................................................................................................................................................. 1 Groundwater Conditions ...................................................................................................................................... 1 Groundwater Levels ......................................................................................................................................... 1 Change in Groundwater in Storage ................................................................................................................. 2 Groundwater Quality ......................................................................................................................................... 3 Water Supply and Production/Deliveries ............................................................................................................ 3 Threats to Water Supply ....................................................................................................................................... 4 SECTION 1: Introduction........................................................................................................................................... 7

1.1 History of Litigation .................................................................................................................................. 7

1.2 Description of the NCMA Technical Group ........................................................................................... 10

1.3 NCMA Technical Group Mission Statement ......................................................................................... 11

1.4 Coordination with Management Areas ................................................................................................. 11

1.5 Development of Monitoring Program .................................................................................................... 13

1.6 Groundwater Monitoring Network ......................................................................................................... 13

1.7 Recent and Ongoing Strategic Initiatives ............................................................................................. 17

1.7.1 Strategic Plan .................................................................................................................................. 17

1.7.2 Central Coast Blue .......................................................................................................................... 17

1.7.3 Phase 1 Groundwater Model ......................................................................................................... 17

1.7.4 Update of the Groundwater Management Agreement ................................................................. 18 SECTION 2: Basin Setting....................................................................................................................................... 19

2.1 Setting ..................................................................................................................................................... 19

2.2 Precipitation ........................................................................................................................................... 19

2.3 Evapotranspiration ................................................................................................................................. 23

2.4 Geology and Hydrogeology .................................................................................................................... 23

2.5 Groundwater Flow and Recharge .......................................................................................................... 24 SECTION 3: Groundwater Conditions .................................................................................................................... 27

3.1 Groundwater Levels ............................................................................................................................... 27

3.1.1 Groundwater Level Contour Maps ................................................................................................. 27

3.1.2 Historical Water Level Trends ........................................................................................................ 30

3.1.3 Sentry Wells and the Deep Well Index .......................................................................................... 30

3.2 Change in Groundwater in Storage ....................................................................................................... 42

3.3 Water Quality .......................................................................................................................................... 45

3.3.1 Quarterly Groundwater Monitoring ................................................................................................ 45

3.3.2 Analytical Results Summary ........................................................................................................... 48 SECTION 4: Water Supply and Production/Delivery ............................................................................................. 55

4.1 Water Supply .......................................................................................................................................... 55

4.1.1 Lopez Lake ...................................................................................................................................... 55

4.1.2 State Water Project ........................................................................................................................ 59

4.1.3 Groundwater ................................................................................................................................... 60

4.1.4 Developed Water ............................................................................................................................ 63

4.1.5 Other Supplies ................................................................................................................................ 64

4.1.6 Total Water Supply Availability ....................................................................................................... 64

4.2 Water Use ............................................................................................................................................... 66

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4.2.1 Agricultural Water Supply Requirements ...................................................................................... 66

4.2.2 Rural Use ......................................................................................................................................... 73

4.2.3 Urban Production for Potable Use ................................................................................................. 74

4.2.4 2024 Groundwater Pumpage ........................................................................................................ 74

4.2.5 Changes in Water Production ........................................................................................................ 77 SECTION 5: Comparison of Water Supply and Water Production ........................................................................ 81 SECTION 6: Threats to Water Supply ..................................................................................................................... 83

6.1 Threats to Local Groundwater Supply ................................................................................................... 83

6.1.1 Declining Water Levels ................................................................................................................... 83

6.1.2 Seawater Intrusion ......................................................................................................................... 84

6.2 Threats to State Water Project Supply .................................................................................................. 88

6.3 Threats to Lopez Lake Water Supply .................................................................................................... 88

6.3.1 Environmental Litigation (San Luis Obispo Coastkeeper vs. County of San Luis Obispo) ......... 88 SECTION 7: Management Activities ....................................................................................................................... 91

7.1 Strategic Plan ......................................................................................................................................... 91

7.1.1 Purpose and Background ............................................................................................................... 91

7.1.2 Mission Statement ......................................................................................................................... 91

7.1.3 Objectives of the NCMA TG ............................................................................................................ 91

7.1.4 Strategic Initiatives and Implementation Plan .............................................................................. 92

7.2 Management Objectives ........................................................................................................................ 92

7.2.1 Share Groundwater Resources and Manage Pumping ................................................................ 93

7.2.2 Enhance Management of NCMA Groundwater ............................................................................. 94

7.2.3 Monitor Supply and Demand and Share Information .................................................................. 95

7.2.4 Manage Groundwater Levels and Prevent Seawater Intrusion ................................................... 98

7.2.5 Protect Groundwater Quality ........................................................................................................100

7.2.6 Manage Cooperatively ..................................................................................................................101

7.2.7 Encourage Water Conservation ...................................................................................................102

7.2.8 Evaluate Alternative Sources of Supply ......................................................................................107 SECTION 8: References ........................................................................................................................................109

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Tables
Table 1. NCMA Technical Group Representatives ................................................................................................ 11 Table 2. Lopez Lake (SLOFCWCD Zone 3 Contractors) Water Entitlements (AFY) ............................................. 55 Table 3. Lopez Lake Municipal Diversion LRRP Reduction Strategy .................................................................. 56 Table 4. Lopez Lake Downstream Release LRRP Reduction Strategy ................................................................ 56 Table 5. Lopez Lake Deliveries, 2024 ................................................................................................................... 59 Table 6. NCMA SWP Table A Allocations, Drought Buffers, Stored Water and 2024 Deliveries ....................... 60 Table 7. NCMA Groundwater Entitlement and Production from Santa Maria River Valley Groundwater Basin, 2024 ........................................................................................................................................................................ 63 Table 8. Baseline (Full Entitlement) Available Urban Water Supplies (AFY) ....................................................... 64 Table 9. Available Urban Water Supply, 2024 (AF) .............................................................................................. 65 Table 10. NCMA Crop Acreages and Calculated Evapotranspiration, 2024 ...................................................... 68 Table 11. Flow Terms Used in Root Zone Routing for IDC Model ....................................................................... 69 Table 12. IDC Model Results of Monthly Applied Water, 2024 ........................................................................... 72 Table 13. Estimated Rural Water Production, 2024 ............................................................................................ 73 Table 14. Historical Urban Water Production for Potable Use (Groundwater and Surface Water) ................... 74 Table 15. NCMA Groundwater Pumpage from Santa Maria River Valley Groundwater Basin, 2024 (AF) ....... 75 Table 16. Historical Total Water Use (Groundwater and Surface Water, AF) ..................................................... 77 Table 17. Water Production by Source, 2024 (AF) ............................................................................................... 82 Figures
Figure 1. Santa Maria River Valley Groundwater Basin ......................................................................................... 8 Figure 2. Northern Cities Management Area .......................................................................................................... 9 Figure 3. Locations of Monitoring Wells ................................................................................................................ 15 Figure 4. Depths of Monitoring Wells .................................................................................................................... 16 Figure 5. Annual Precipitation 1950 to 2024 ...................................................................................................... 20 Figure 6. Location of Precipitation Stations .......................................................................................................... 21 Figure 7. Monthly and Average Precipitation and Evapotranspiration ................................................................ 22 Figure 8. Groundwater Elevation Contours Spring 2024 ..................................................................................... 28 Figure 9. Groundwater Elevation Contours Fall 2024 ......................................................................................... 29 Figure 10. Selected Hydrographs .......................................................................................................................... 31 Figure 11. Sentry Well Hydrographs ...................................................................................................................... 32 Figure 12. Hydrograph of Deep Well Index Elevation ........................................................................................... 34

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Figure 13. Water Elevation, Conductivity, and Temperature, Well 24B03 ......................................................... 35 Figure 14. Water Elevation, Conductivity, and Temperature, Well 30F03 ......................................................... 36 Figure 15. Water Elevation, Conductivity, and Temperature, Well 30N02 ......................................................... 37 Figure 16. Water Elevation, Conductivity, and Temperature, Well 36L01 ......................................................... 38 Figure 17. Water Elevation, Conductivity, and Temperature, Well 36L02 ......................................................... 39 Figure 18. Water Elevation, Conductivity, and Temperature, Well 32C03 ......................................................... 40 Figure 19. Change in Groundwater Elevation, Deep Aquifer System, April 2023 to April 2024 ....................... 43 Figure 20. Change in Groundwater Elevation, Alluvial Aquifer, April 2023 to April 2024 ................................. 44 Figure 21. Chloride Concentrations in Monitoring Wells ..................................................................................... 46 Figure 22. Total Dissolved Solids Concentrations in Monitoring Wells ............................................................... 47 Figure 23. Piper Diagrams of Water Quality in Select Monitoring Wells (4-page figure, one for each quarter) ................................................................................................................................................................................. 50 Figure 24. Locations of Municipal Production Wells ............................................................................................ 62 Figure 25. NCMA Agricultural Land 2024 ............................................................................................................. 67 Figure 26. 2024 Estimated Agricultural Water Demand and Monthly Precipitation at the SLO No. 795 Gauge ................................................................................................................................................................................. 71 Figure 27. Municipal Water Use by Source ........................................................................................................... 76 Figure 28. Total Water Use (Urban, Rural, Agricultural) by Source ..................................................................... 78 Figure 29. Historical TDS, Chloride, and Sodium, Index Wells and 30N03 ........................................................ 85 Figure 30. Historical TDS, Chloride, and Sodium, Wells 30N02, MW-Blue and 36L01..................................... 86 Appendix
Appendix A NCMA Sentry Well Water Level and Water Quality Data

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Abbreviations and Acronyms
2005 Stipulation 2005 Stipulation for the Santa Maria River Valley Groundwater Basin Adjudication 2008 Judgement January 25, 2008 Judgment After Trial
2023 Annual Report Northern Cities Management Area 2023 Annual Monitoring Report AF acre-feet
AFY acre-feet per year
Arroyo Grande City of Arroyo Grande
APW advanced purified water
basin Santa Maria River Valley Groundwater Basin
bgs below ground surface
CCBRRWA Central Coast Blue Regional Recycled Water Authority CIMIS California Irrigation Management Information System County San Luis Obispo County
Court Superior Court of California, County of Santa Clara CSA County Service Area
CUP Consumptive Use Program
DDW Division of Drinking Water
Delta Sacramento-San Joaquin Delta
DRI Desert Research Institute
DWR California Department of Water Resources
ET evapotranspiration
Grover Beach City of Grover Beach
IDC 2015 Integrated Water Flow Model Demand Calculator
IRWMP Integrated Regional Water Management Plan
IWFM 2015 Integrated Water Flow Model
LRRP Low Reservoir Response Plan
MLLW mean lower low water
MSL mean sea level
NAVD 88 North American Vertical Datum of 1988
NCMA Monitoring
Program
Monitoring Program for the Northern Cities Management Area NCMA Northern Cities Management Area
NCSD Nipomo Community Services District
Nipomo station Nipomo Station (No. 202)
NMMA Nipomo Mesa Management Area

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NWP Nacimiento Water Project
OCSD Oceano Community Services District
PG&E Pacific Gas & Electric
Pismo Beach City of Pismo Beach
RWFPS Recycled Water Facility Planning Study
SGMA Sustainable Groundwater Management Act
SLOFCWCD County of San Luis Obispo Flood Control and Water Conservation District SMCL Secondary Maximum Contaminant Limit
SMGBMA Santa Maria Groundwater Basin Management Area
SMRVGB Santa Maria River Valley Groundwater Basin
SMVMA Santa Maria Valley Management Area
SNMP Salt and Nutrient Management Plan
SSLOCSD South San Luis Obispo County Sanitation District Strategic Plan NCMA Strategic Plan
SWP California State Water Project
TAC Technical Advisory Committee
TDS total dissolved solids
TG NCMA Technical Group
UWMP Urban Water Management Plan
WSC Water Systems Consulting, Inc.

WSCP Water Shortage Contingency Plan
WSPDP Water Supply, Production, and Delivery Plan
WWTP wastewater treatment plant

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Executive Summary
The 2024 Annual Monitoring Report for the Northern Cities Management Area (NCMA) (Annual Report) is prepared pursuant to the requirements of the 2005 Stipulation for the Santa Maria River Valley Groundwater Basin Adjudication (2005 Stipulation) and the January 25, 2008, Judgment After Trial (2008 Judgment). This 2024 Annual Report provides an assessment of hydrologic conditions for the NCMA based on data collected during the calendar year of record. As specified in the Judgment, the NCMA agencies, consisting of the cities of Arroyo Grande, Grover Beach, and Pismo Beach, and the Oceano Community Services District (OCSD), regularly monitor groundwater in the NCMA and analyze other data pertinent to water supply and demand, including the following:
Land and water use in the Santa Maria River Valley Groundwater Basin (SMRVGB or basin) Sources of supply to meet water demand
Groundwater conditions (including water levels and water quality) Amount and disposition of NCMA water supplies that are not groundwater Results of the data compilation and analysis for calendar year 2024 are documented and discussed in this 2024 Annual Report.

Groundwater Conditions
During 2024, groundwater elevations generally increased in the NCMA portion of the SMRVGB in response to above-average rainfall received during the 2022/2023 and 2023/2024 winter seasons. The rise in water level is not only a direct result of above-average precipitation but is also attributed groundwater recharge associated with the prolonged spill event of Lopez Lake from February 2024 through June 2024. Additionally, ongoing efforts by all NCMA agencies to minimize groundwater extraction and maximize surface water supply sources while maintaining water conservation practices and requirements implemented during the recent drought have contributed to increased groundwater elevations.

Groundwater Levels
The most significant issue potentially impacting the groundwater supply in the NCMA is seawater intrusion.

The NCMA agencies utilize the Deep Well Index (DWI) to determine if aquifer conditions indicate susceptibility to seawater intrusion. The DWI is calculated by averaging synoptic measurements of groundwater elevation in the three NCMA deep sentry wells near the coastline: wells 24B03, 30F03, and 30N02. A Deep Well Index value above 7.5 feet North American Vertical Datum 1988 (NAVD 88)1 indicates that sufficient groundwater flow occurs from the east to the coastline to prevent seawater intrusion. History has shown that a prolonged period in which the Deep Well Index level is below 7.5 feet indicates groundwater conditions that pose a risk of seawater intrusion. The following are evaluations of groundwater levels through the seasons in calendar year 2024:
Spring 2024. In the urbanized areas north of Arroyo Grande Creek, groundwater is extracted from the deep groundwater aquifers of the Paso Robles Formation and the Careaga Sand. The groundwater elevation contours in the deep aquifer system in the spring of 2024 generally showed a westerly to southwesterly 1 Note that 0.0 feet (NAVD 88) is 2.72 feet lower than mean sea level (MSL) and is 0.08 feet above the mean lower low water (MLLW) (which can be thought of as the average height of the lowest tides), as recorded at the Port San Luis tide station datum ( https://tidesandcurrents.noaa.gov/datums.html?id=9412110) .

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groundwater flow (see Figure 8, on page 28). Spring 2024 groundwater elevations in the deep aquifer system main production zone along the coast ranged from 11.3 to 18.1 feet above mean sea level (NAVD 88).

The Cienega Valley is in the central area of the NCMA, generally south of Arroyo Grande Creek. Most groundwater pumping in this area is from the relatively shallow (less than 100 feet deep) alluvial aquifer.

Agricultural groundwater production typically results in a seasonal drawdown of the alluvial aquifer in the valley. Historically, a portion of the recharge to the alluvial aquifer of the Cienega Valley came from the Paso Robles Formation aquifer on the Nipomo Mesa. However, this recharge mechanism appears to be slowing because of declining water levels on the Nipomo Mesa (see Section 2.5). This reduction of subsurface inflow exacerbates the seasonal drawdown of the alluvial aquifer in the Cienega Valley.

Groundwater elevations in the alluvial aquifer in the Cienega Valley ranged from 10 feet to more than 50 feet above mean sea level (NAVD 88) in spring 2024. These data show an overall increase in alluvial groundwater elevations from April 2023 to April 2024.
Fall 2024. Groundwater level contours for October 2024 are presented in Figure 9, on page 29. October 2024 groundwater elevations in the deep aquifer system main production zone along the coast ranged from 10.7 to 15.9 feet above 0.0 feet (NAVD 88).

Groundwater elevations in the alluvial aquifer within the Cienega Valley in October 2024 were 2 to 12 feet lower than elevations at the start of the irrigation season in April 2024, which is a typical seasonal response to the irrigation season.
Deep Well Index. In 2024, the DWI started the year above the trigger value with an index value of 12.3 feet in January. The index value seasonal high occurred in April at 13.8 feet, and then generally declined throughout the rest of the year, finishing the year at about 11.51 feet (NAVD 88) (October 2024). NCMA/NMMA Boundary. The water elevation in the San Luis Obispo County monitoring well (Well 32C03), which was installed to monitor aquifer conditions along the NCMA/NMMA boundary, typically exhibits regular seasonal fluctuations. The groundwater elevation in 2024 continued to trend upward, consistent with reported groundwater levels in 2023. In 2024, the groundwater elevation in well 32C03 ranged from

12.8 feet (October 2024) to 23.0 feet (April 2024) above mean sea level (NAVD 88). This is a reversal from the seasonal low levels observed in 2021 and 2022, which were below 0.0 feet (NAVD 88). The 2024 seasonal high-water level in well 32C03 is the highest seen since 2012.

Change in Groundwater in Storage
The change in groundwater in storage in the NCMA portion of the SMRVGB between April 2023 and April 2024 is estimated by comparing water level grids created for these periods and calculating the volume change from April 2023 to April 2024. The same selection of wells is used from the previous year to the current year.

Separate estimates of change in groundwater in storage were computed for both the deep aquifer system and the alluvial aquifer and then summed to represent the total NCMA estimated change in groundwater in storage. A comparison of April water levels was chosen to comply with the California Department of Water Resources (DWR) recommended reporting requirements.2
An increase in groundwater in storage reflects a net increase in water levels across the aquifer. From April 2023 to April 2024, the NCMA portion of the SMRVGB experienced an overall net increase of groundwater in 2 On September 16, 2014, Governor Jerry Brown signed into law a three-bill legislative package, composed of Assembly Bill 1739 (Dickinson), Senate Bill (SB) 1168 (Pavley), and SB 1319 (Pavley), collectively known as the Sustainable Groundwater Management Act (SGMA).

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storage. The net increase in groundwater in storage from April 2023 to April 2024 is calculated to be approximately 530 acre-feet (AF); that is, there was approximately 530 AF more groundwater stored in the NCMA portion of the SMRVGB in April 2024 than in April 2023. This increase in groundwater in storage may be attributable to groundwater recharge from above-average precipitation received during the winter of 2023/2024 and from prolonged infiltration from Arroyo Grande Creek during the Lopez Lake spill event, which extended from February through June 2024.

Groundwater Quality
Analytical results of key water quality data (chloride, total dissolved solids [TDS], and sodium) in 2024 were generally consistent with historical concentrations and observed ranges of constituent concentrations. None of the water quality results from monitoring events throughout 2024 indicate an incipient episode or immediate threat of seawater intrusion.

Water Supply and Production/Deliveries
Total water use in the NCMA in 2024 (including urban use by the NCMA agencies plus agricultural irrigation and private pumping by rural water users) was 7,783 AF. Of this amount, Lopez Lake deliveries accounted for 4,173 AF, California State Water Project deliveries totaled 661 AF, and groundwater pumping from the NCMA portion of the SMRVGB accounted for approximately 2,949 AF. The City of Arroyo Grande produced 0 AF from its Pismo Formation wells, outside the SMRVGB, in 2024. The breakdown is shown in Table ES-1.

Urban water use in 2024 among the NCMA agencies was 5,356 AF, the second-lowest usage in at least the last 20 years. Urban water use in the past 18 years has ranged from 5,240 AF (2023) to 8,982 AF (2007).

There has been an overall decline in urban production since 2007, although there have been slight increases since 2016. The decline in pumpage since 2013 was, at least in part, a result of the statewide order by the governor to reduce the amount of water used in urban areas by 20 percent. That goal was achieved locally by conservation activities implemented by the NCMA agencies, and the relatively low urban water use has been maintained since then.

Agricultural acreage in the NCMA portion of the SMRVGB has remained relatively constant for more than 20 years. Thus, the annual applied water requirement for agricultural irrigation has been relatively stable, although it varies with climatic conditions. Acknowledging the variability resulting from climatic conditions, agricultural applied water is not expected to change significantly given the relative stability of applied irrigation acreage and cropping patterns in the NCMA. Changes in rural domestic pumping have not been significant.

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Table ES-1. Water Production by Source (AF), 2024
Agency Lopez Lake
State
Water
Project
SMRVGB
Groundwater
Other
Supplies1 Total
Urban Area
Arroyo Grande 1,965 0 59 0 2,024
Grover Beach 791 0 436 0 1,227
Pismo Beach 1,099 380 15 0 1,494
OCSD 318 281 12 0 611
Urban Water Use Total 4,173 661 522 0 5,356
Non-Urban Area
Agricultural Irrigation
Applied Water 0 0 2,307 0 2,307
Rural Water Users 0 0 80 0 80
Non-potable Applied
Irrigation Water (Arroyo
Grande)
0 0 40 0 40
Total 4,173 661 2,949 0 7,783
Notes
1 The category “Other Supplies” includes groundwater pumped from outside the NCMA boundaries.

AF = acre-feet NCMA = Northern Cities Management Area OCSD = Oceano Community Services District SMRVGB = Santa Maria River Valley Groundwater Basin

Threats to Water Supply
Total groundwater pumping (urban, agriculture, and rural domestic) from the SMRVGB in the NCMA was 2,949 AF in 2024, which is 31 percent of the court-accepted3 9,500 acre-feet per year (AFY) long-term safe yield of the NCMA portion of the SMRVGB.

When pumping is less than the safe yield of an aquifer, groundwater in storage should generally increase and result in an increase in groundwater levels. As such, groundwater elevations throughout the NCMA portion of the SMRVGB should rise if several consecutive years of groundwater pumping occur at 30 to 40 percent of the safe yield, which has been the case in the NCMA for the past decade. However, data from the past decade indicates that the aquifer is still in a tenuous position with respect to the threat of seawater intrusion.

According to the DWR Bulletin 63-3 report, both the Paso Robles Formation aquifer and the lower confined portion of the Cienega Valley alluvial aquifer are recharged primarily from subsurface groundwater inflow from the east, where the overlying confining layers are thin to nonexistent (DWR, 1970). These recharge areas to the east include inland reaches of Arroyo Grande Valley and portions of Nipomo Mesa (DWR, 1970). Any

3 The calculated, consensus safe yield value of 9,500 AFY for the NCMA portion of the SMRVGB was formalized in the 2002 Settlement Agreement through affirmation of the 2002 Groundwater Management Agreement among the NCMA agencies, which is described in more detail in Section 1.1 of this report.

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increase in regional pumping or any other changes that reduce recharge from the east could result in a groundwater deficit in the NCMA and vulnerability to seawater intrusion.

Historically, groundwater flowed westward from higher elevations in inland areas toward the ocean, thereby mitigating seawater intrusion. DWR (2002) documented a pumping depression in Spring 1975 in the deep aquifer system near Black Lake Canyon within the NMMA. By Spring 1995, DWR (2002) documented the pumping depression had expanded and reversed the coastward groundwater gradient. The groundwater pumping depression was documented in the first NMMA Annual Reports in 2008–2009.4 The development of a landward gradient in the southern portion of the NCMA, caused by the pumping depression in the NMMA, reduces the historical recharge volume of subsurface inflow into the NCMA from Nipomo Mesa. This reduction of subsurface inflow to the NCMA creates conditions more likely to result in seawater intrusion in the NCMA and NMMA and it exacerbates the seasonal drawdown of the alluvial aquifer in the Cienega Valley.

During 2024, the groundwater flow direction in the northern portion of the NCMA was predominantly toward the ocean. However, along the southeast corner of the NCMA at the boundary with NMMA, there is evidence of landward flow from NCMA into NMMA. See Section 3.1 for a discussion of groundwater levels during the 2024 calendar year.

During 2024, there were no indications of seawater intrusion. See Section 3.3 for a discussion of water quality analytical results during the 2024 calendar year.
4 As documented in NMMA annual reports, available at https://ncsd.ca.gov/resources/reports-by-subject . (Accessed January 30, 2024.)

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SECTION 1: Introduction
This Northern Cities Management Area 2024 Annual Monitoring Report (2024 Annual Report or Annual Report) summarizes hydrologic conditions for calendar year 2024 in the Northern Cities Management Area (NCMA) of the Santa Maria River Valley Groundwater Basin (SMRVGB or the basin) in San Luis Obispo County (County), California (Figure 1, on page 8). This report was prepared on behalf of four public agencies collectively referred to as the Northern Cities, which include the cities of Arroyo Grande (Arroyo Grande), Grover Beach (Grover Beach), Pismo Beach (Pismo Beach), and the Oceano Community Services District (OCSD)5,6 (Figure 2, on page 9). These agencies, along with local landowners, the County, and the County of San Luis Obispo Flood Control and Water Conservation District (SLOFCWCD) have managed local surface water and groundwater resources since the late 1970s to preserve the long-term integrity of water supplies.

1.1 History of Litigation
The rights to pump groundwater from the SMRVGB have been in litigation (adjudication) since the late 1990s.

The physical solution set forth in the 2005 Stipulation for the Santa Maria River Valley Groundwater Basin Adjudication (2005 Stipulation) and the January 25, 2008, Judgment After Trial (2008 Judgment)7 established requirements and goals for the management of the entire SMRVGB. The Superior Court of California, County of Santa Clara (Court) established three separate management areas, including the NCMA, the Nipomo Mesa Management Area (NMMA), and the Santa Maria Valley Management Area (SMVMA). The Court mandated that each management area form a technical group to monitor the groundwater conditions of its area, to continuously assess the hydrologic conditions of each area, and to prepare an annual report each year to provide the Court with a summary of the previous year’s conditions, actions, and threats.

The requirements for the annual report, as directed by the Court in the 2005 Stipulation (June 30, 2005, version, paragraph IV.D.3), are as follows:

Within one hundred and twenty days after each Year end, the Management Area Engineers will file an Annual Report with the Court. The Annual Report will summarize the results of the Monitoring Program, changes in groundwater supplies, and any threats to Groundwater supplies. The Annual Report shall also include a tabulation of Management Area water use, including Imported Water availability and use, Return Flow entitlement and use, other Developed Water availability and use, and Groundwater use. Any Stipulating Party may object to the Monitoring Program, the reported results, or the Annual Report by motion. 5 Each agency may also be individually referred to as an NCMA agency. 6 Portions of Arroyo Grande and Pismo Beach extend outside the NCMA. 7 Santa Maria Valley Water Conservation District v. City of Santa Maria, et al., Case #1-97-CV-770214 Filing #G-79046. (Cal., 2015).

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Date: January 28, 2020 Data Sources:

LEGENDNorthern Cities Management AreaNipomo Mesa Management AreaSanta Maria Valley Management AreaSanta Maria River Valley Groundwater BasinCounty Borders Santa Maria River Valley Groundwater Basin
FIGURE 1
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Date: February 26, 2020 Data Sources: DWR, NCMA, USGS, California Geological Survey, ESRI LEGENDNorthern Cities Management AreaNipomo Mesa Management AreaSanta Maria River Valley Groundwater BasinFaults (dashed where inferred)Streams Northern Cities Management Area
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This 2024 Annual Report satisfies the requirements of the Court. The annual report for each calendar year (January 1 to December 31) is submitted to the Court by April 30 of the following calendar year, pursuant to the 2005 Stipulation. Although the 2024 Annual Report is also published to the California Department of Water Resources (DWR) adjudicated basin reporting website, there is no deadline for submittal of annual reports for adjudicated basins.8
The collaborative water supply management approach of the NCMA agencies was recognized by the Court in the 2002 Groundwater Management Agreement (which was based on the 1983 Gentlemen’s Agreement), formalized in the Settlement Agreement Between Northern Cities, Northern Cities Landowners, and Other Parties (2002 Settlement Agreement or Settlement Agreement) and incorporated in the 2005 Stipulation. On June 30, 2005, the 2005 Stipulation, which included the 2002 Settlement Agreement, was agreed upon by numerous parties, including the NCMA agencies. The approach was then adopted by the Court in its 2008 Judgment. Although appeals to that decision were filed, a subsequent decision by the Sixth Appellate District (filed November 21, 2012) upheld the Judgment. On February 13, 2013, the Supreme Court of California denied a petition to review the decision.

Pursuant to the Court’s continuing jurisdiction, Arroyo Grande, Pismo Beach, and Grover Beach filed a motion on September 29, 2015, requesting that the Court impose moratoriums on certain water extraction and use by stipulating parties within the NMMA. Judge Kirwan denied the motion without prejudice. He did, however, order the parties to meet and confer to address the issues raised in the motion. There have been no meetings under the meet and confer process over the past few years. There are no updates to report for 2024. A motion to appoint a technical advisor to the Court occurred in 2021, which resulted in the Court selection of a technical advisor. The order by the Court precipitated a series of meetings and collaborative actions between the NCMA and NMMA agencies, including the tentative formation of a Seawater Intrusion Working Group (now inactive) to discuss the threat and potential solutions for possible seawater intrusion.

1.2 Description of the NCMA Technical Group
Pursuant to a requirement in the 2005 Stipulation, the NCMA Technical Group (TG) was formed (Paragraph IV.C and Paragraph VII). The TG is composed of representatives of each of the NCMA agencies, as listed in Table 1.
8 The link to the reporting system is available on this DWR page: https://water.ca.gov/Programs/Groundwater- Management/SGMA-Groundwater-Management/Adjudicated-Areas.

Applicability of GSP DWR reporting deadline to adjudicated basin annual reports is based on a DWR hosted Adjudication Area Reporting System Workshop on May 9, 2024.

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Table 1. NCMA Technical Group Representatives
Agency Representative
City of Arroyo Grande
Shannon Sweeney
City Engineer
Shane Taylor
Utilities Manager
City of Grover Beach
Gregory A. Ray, PE
Director of Public Works/City Engineer
R.J. (Jim) Garing, PE
Consulting City Engineer for Water and Sewer
City of Pismo Beach Rosemarie Gaglione, PE
Director of Public Works
Oceano Community Services
District
Peter Brown
General Manager
Notes
NCMA = Northern Cities Management Area PE = Professional Engineer The NCMA TG contracts with Water Systems Consulting, Inc. (WSC), to serve as staff extension to assist the TG in its roles and responsibilities in managing the water supply resources. The TG also contracts with GSI Water Solutions, Inc., and its subconsultant partner, GEI Consultants, Inc., to conduct the quarterly groundwater monitoring and sampling tasks, evaluate water demand and available supply, identify threats to water supply, and assist the TG in preparation of the annual report.

1.3 NCMA Technical Group Mission Statement
The NCMA TG developed the following mission statement to help guide ongoing initiatives and to capture the requirements outlined in the 2002 Groundwater Management Agreement, 2002 Settlement Agreement, 2005 Stipulation, and 2008 Judgment:

Preserve and enhance the sustainability of water supplies for the Northern Cities Area by:
Enhancing supply reliability
Protecting water quality
Maintaining cost-effective water supplies
Advancing the legacy of cooperative water resources management Promoting conjunctive use

1.4 Coordination with Management Areas
Since 1983, management of the NCMA has been based on cooperative efforts of the four NCMA agencies in continuing collaboration with the County, SLOFCWCD, and other local and state agencies. Specifically, the

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NCMA agencies have jointly monitored and managed their groundwater production and, in cooperation with the SLOFCWCD, invested in surface water supplies to reduce dependence on groundwater pumping and protect the groundwater resource. The NCMA TG hosts a meeting each year with agricultural representatives from throughout the NCMA to discuss the status of the basin, present the findings of the annual report, and develop collaborative strategies for protecting the groundwater resource. In addition to the efforts discussed in this 2024 Annual Report, cooperative management occurs through many means, including communication by the NCMA agencies in their respective public meetings, participation in the SLOFCWCD Zone 39 Advisory Committee (related to the management and operation of Lopez Lake, which is described further in Section 4.1.1), and participation in the Water Resources Advisory Committee (the County-wide advisory panel on water issues). The NCMA agencies are active participants in current and ongoing integrated regional water management efforts and participated in preparation and adoption of the 2019 update of the San Luis Obispo County Integrated Regional Water Management Plan (IRWMP). The IRWMP promotes integrated regional water management to ensure sustainable water uses, reliable water supplies, better water quality, environmental stewardship, efficient urban development, protection of agriculture, and a strong economy.

Since the 2008 Judgment, the NCMA TG has taken the lead in cooperative management of its management area. The NCMA TG has met monthly (at a minimum) for many years and continued to do so throughout 2024.

The TG also participates in the Santa Maria Groundwater Basin Management Area (SMGBMA) technical subcommittee, formed in 2009; however, no meetings of the SMGBMA were held in 2024. The purpose of the SMGBMA technical subcommittee is to coordinate efforts among the three management areas (NCMA, NMMA, SMVMA) such as sharing data throughout the year and during preparation of the annual report, reviewing and commenting on technical work efforts of other management areas, standardizing monitoring protocols, considering projects and grant opportunities of joint interest and benefit, and sharing information and data among the managers of the three management areas.

The outcomes of the motion that Arroyo Grande, Pismo Beach, and Grover Beach filed on September 29, 2015 (see Section 1.1), include increased discussion and collaboration between the NCMA and NMMA. One of the initiatives was the formation of an NCMA-NMMA Management Coordination Committee that has met several times since 2018 to discuss items of mutual concern and develop strategies for addressing the concerns.

Another area of increased mutual collaboration between the NCMA and NMMA was the formation in 2016 of a technical team to collaboratively develop a single data set of water level data points as part of preparing a consistent set of semiannual water level contour maps for the NCMA and NMMA. Those efforts continued into and throughout 2024 and resulted in the development of consistent water level contouring (and enhanced understanding of groundwater conditions) throughout the NCMA and NMMA. 9 Flood Control Zone 3 (Lopez Project) is operated by SLOFCWCD to operate Lopez Reservoir for municipal and agricultural water supplies. It was established to operate the Lopez water supply system and is a wholesale supplier. The contractors in Zone 3 include the communities of Oceano, Grover Beach, Pismo Beach, Arroyo Grande, and County Service Area (CSA) 12 (including the Avila Beach area).

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1.5 Development of Monitoring Program
The 2008 Judgment orders the stipulating parties to comply with all terms of the 2005 Stipulation. As specified in the Judgment and as outlined in the Monitoring Program for the Northern Cities Management Area (Todd, 2008) (NCMA Monitoring Program), the NCMA agencies are to conduct groundwater monitoring of wells in the NCMA. In accordance with requirements of the Judgment, the NCMA agencies collect and analyze data pertinent to water supply and demand, including the following:
Land and water use in the NCMA portion of the SMRVGB
Sources of supply to meet those uses
Groundwater conditions (including water levels and water quality) Amount and disposition of other sources of water supply in the NCMA The NCMA Monitoring Program requires that the NCMA agencies gather and compile pertinent information on a calendar-year basis; this is accomplished through data collected by NCMA agencies (including necessary field work), the SLOFCWCD, and by other public agencies. Periodic reports, such as Urban Water Management Plans (UWMPs) prepared by Arroyo Grande, Grover Beach, and Pismo Beach, provide information about demand, supply, and water supply facilities. Annual data are added to the comprehensive NCMA database and analyzed. Results of the data compilation and analysis for 2024 are documented and discussed in this 2024 Annual Report.

As shown in Figure 1, on page 8, the NCMA represents the northernmost portion of the SMRVGB as defined in the 2005 Stipulation. Adjoining the NCMA to the south and east is the NMMA; the SMVMA encompasses the remainder of the SMRVGB. Figure 2, on page 9, shows the locations of the four NCMA agencies in the NCMA.

1.6 Groundwater Monitoring Network
The NCMA Monitoring Program includes (1) compilation of groundwater elevation data from the County, (2) water quality and groundwater elevation monitoring data from the network of sentry and monitoring wells in the NCMA, and (3) groundwater elevation data from municipal pumping wells. Analysis of these data is summarized below in accordance with the NCMA Monitoring Program (Todd, 2008) and as modified as additional well data and data sources have become available over the years.

Approximately 150 wells within the NCMA were monitored for water levels by the County at some time during the past few decades. The County currently monitors the water level in 50 wells within the NCMA on a semiannual basis in April and October. The County monitoring program includes four sentry well clusters (piezometers) along the coast, a four-well cluster in Oceano, and County Monitoring Well No. 3 (12N/35W- 32C03) (County Monitoring Well No. 3 [32C03]) located on the eastern NCMA boundary between the NCMA and NMMA (Figure 3, on page 15). The County monitors more than 125 additional wells in the NMMA portion of the SMRVGB within the County. Beginning in 2009, the NCMA agencies initiated a quarterly sentry well monitoring program to supplement the County’s semiannual schedule.

To monitor overall changes in groundwater conditions, representative wells within the NCMA were selected for the preparation of hydrographs and evaluation of water level changes. Wells were selected based on the following criteria:
The wells must be part of the County’s current monitoring program or part of a public agency’s regular monitoring program.
Detailed location information must be available.

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Construction details of the wells must be available.
The locations of the wells should have a wide geographic distribution. The historical record of water level data must be long and relatively complete.

Many of the wells that have been used in the program are production wells that were not designed for monitoring purposes (i.e., the wells are screened across various production zones). Moreover, many of the wells are active production wells or are located near active wells and are, therefore, potentially subject to localized pumping effects that result in measurements that are lower than the regionally representative water level. These effects are not always apparent at the time of measurement, and data cannot easily be identified as representing static groundwater levels in specific zones (e.g., unconfined or deep confined to semi- confined). Therefore, data should be considered in its entirety when developing a general representation of groundwater conditions.

The “sentry” wells (32S/12E-24Bxx, 32S/13E-30Fxx, 32S/13E-30Nxx, and 12N/36W-36Lxx) are a critical element of the groundwater monitoring network and are designed to provide an early warning system to identify potential seawater intrusion in the aquifer (Figure 3, on page 15). Each sentry well consists of a cluster of multiple wells that allows for the measurement of groundwater elevation and quality from discrete depths.

Also shown in Figure 3, on page 15, is the OCSD observation well cluster, a dedicated monitoring well cluster located just seaward of OCSD production well 810, and County Monitoring Well No. 3 (32C03). Figure 4, on page 16, shows the depth and well names of the sentry well clusters, the OCSD observation well cluster, and County Monitoring Well No. 3 (32C03).

Traditionally, the wells were divided into three basic depth categories—shallow, intermediate, and deep—to describe the relative depths of each monitoring well within the cluster. The basic depth categories do not necessarily describe the geologic unit and relative depth of the unit that the screened portion of the well monitors. It is important, however, to recognize and identify the geologic unit that each well monitors. The water level responses and water quality changes are quite different in wells that monitor the shallow alluvial unit (24B01, 30F01, and 30N01), the Paso Robles Formation (24B02, 30F02, 30N02, 30N03, 36L01, OCSD MW-Green, OCSD MW-Blue, and 32C03), and the deeper Careaga Sand (24B03, 30F03, 36L02, OCSD MW-Silver, and OCSD MW-Yellow 11). The significance of this level of differentiation will be studied more extensively in the future.

Since the sentry well monitoring program began in 2009, 63 monitoring events have been conducted. These monitoring events include the collection of synoptic groundwater elevation data and water quality samples for laboratory analysis.
10 MW-Yellow, the deepest completion in the OCSD well cluster has been removed from the NCMA Monitoring Program as a result of apparent casing failure. See Section 3.1.3, for more details. 11 Note that OCSD MW-Yellow was removed from the monitoring program in the second quarter of 2022 (see details in Section 3.3.1).

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FIGURE 4. DEPTHS OF MONITORING WELLS
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1.7 Recent and Ongoing Strategic Initiatives

1.7.1 Strategic Plan
An NCMA Strategic Plan (Strategic Plan) was first developed in 2014 to provide the NCMA TG with a mission statement to guide future initiatives, provide a framework for identifying and communicating water resource planning goals and objectives, and formalize a 10-year work plan for implementation of those efforts (WSC, 2014). Several key objectives were identified related to enhancing water supply reliability, improving water resource management, and increasing effective public outreach. Implementation of these efforts continued throughout 2024. Several key strategies were identified by the TG for improving the sustainability of the water resource. Strategic initiatives were developed for each key strategy. The TG then developed an implementation plan for the key strategies that include current, short-term, and long-term time frames for initiatives that could be completed within 1 year, 5 years, and more than 5 years.

Work began in 2024 to update the 2020 Strategic Plan, which is anticipated to be completed in the first half of 2025.

A more detailed description of the Strategic Plan is provided in Section 7.1.

1.7.2 Central Coast Blue
Central Coast Blue is a regional recycled water project with original partner agencies consisting of Arroyo Grande, Grover Beach, and Pismo Beach, with Pismo Beach serving as the lead agency. The OCSD and South San Luis Obispo County Sanitation District (SSLOCSD) are currently not members of the joint powers authority, however, both agencies have expressed support for the project and are key stakeholders in this regional project. The project is intended to develop a sustainable, drought-resilient water supply and help protect the SMRVGB. On March 18, 2024, the CCBRRWA Board of Directors received an update on project costs, funding, and financing for the proposed Central Coast Blue Project. Significant increases in project costs, a loss of state grant funding, and improvements in local water supply conditions have prompted leaders to stop project design and permitting until the impacts of these recent developments can be evaluated. (CCBRRWA, 2024) In response to these funding challenges, the partner agencies will re-evaluate their current water supply needs and consider Project alternatives. Arroyo Grande and Grover Beach withdrew from the Central Coast Blue Project as originally conceived in 2024. Additionally, the program management team is exploring options that would reduce Project costs and leaders are advocating to secure additional grants. As a result, project construction—initially planned to break ground in summer 2024—has been delayed (CCBRRWA, 2024).

1.7.3 Phase 1 Groundwater Model
As part of Central Coast Blue planning and technical studies, a localized groundwater flow model (the Phase 1A model) was developed for the northern portion of the NCMA. The Phase 1A model evaluated the concept of injecting advanced purified water (APW) into the SMRVGB to increase aquifer recharge, improve water supply reliability, and help prevent future occurrences of seawater intrusion (CHG, 2017). Based on the results of the Phase 1A model and through funding from the SSLOCSD Supplemental Environmental Program, work was initiated in 2017 and continued through 2020 for the development of the Phase 1B groundwater flow model (Geoscience Support Services, 2019). The domain of the Phase 1B model covers the entire NCMA, NMMA, and the portion of the SMVMA north of the Santa Maria River.

The original purpose of the Phase 1B model was to expand the Phase 1A model and use the expanded model to evaluate a series of groundwater injection and extraction scenarios to support planning for Central Coast

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Blue. The Phase 1B model was used to (1) more completely understand the groundwater conditions of the NCMA portion of the SMRVGB, (2) understand the groundwater flow dynamics and components of the groundwater water balance of the aquifer, (3) identify the locations of the proposed injection wells, (4) quantify the amount of water that can be injected, (5) evaluate strategies for preventing seawater intrusion, and (6) develop estimates of the overall yield that the project would produce.

The Phase 1C Groundwater Model, developed in 2021 (Geoscience Support Services, 2021), re-evaluated the location of the offshore seawater-freshwater interface in light of airborne geophysical studies conducted off the coast of Pismo Beach. The Model continues to be a tool for the NCMA agencies to further evaluate basin yield and basin management initiatives.

In 2024 the NCMA TG indicated their desire to utilize the Groundwater Model for forward simulations to assist with planning for time periods of 1 to 3 years in the future. This would enable the TG to use the model to evaluate anticipated future conditions annually, as described in the Adaptive Groundwater Management Plan (see Section 1.7.4). To implement this plan, the model was updated from December 2016 to March 2024 (an addition of 87 stress periods) so that current conditions are represented. Work on the model update began in 2024. When the effort is completed, a Technical Memorandum will be prepared documenting the particular parameters that were updated and the methodology for doing so.

1.7.4 Update of the Groundwater Management Agreement
Throughout 2022, the TG discussed various components and approaches to updating the 2002 Groundwater Management Agreement. A draft Groundwater Management Agreement update was produced in 2023 but was not finalized pending the completion of a companion Adaptive Groundwater Management Plan. Work on the Adaptive Groundwater Management Plan and finalization of the updated Groundwater Management Agreement continued in 2024. The TG anticipates finalizing the NCMA Adaptive Groundwater Management Plan and Management Agreement in 2025.

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SECTION 2: Basin Setting

2.1 Setting
The Tri-Cities Mesa 12 in the northern portion of the NCMA is predominantly urban (residential/commercial).

The Cienega Valley, a low-lying coastal stream and valley regime, is the area south of Arroyo Grande Creek in the central part of the area and is predominantly agricultural. The southern and southwestern portions of the area are composed of beach dunes and small lakes primarily managed by the California Department of Parks and Recreation as a recreational area and a sensitive species habitat.

2.2 Precipitation
Each year, climatological and hydrologic (streamflow) data for the NCMA are added to the NCMA database.

Annual precipitation from 1950 to 2024 is presented in Figure 5, on page 20.

Historical rainfall data are compiled monthly for the following two stations:13 DWR California Irrigation Management Information System (CIMIS) Nipomo Station (No. 202) (Nipomo station) for 2006 to present
San Luis Obispo County-operated rain gauge (No. SLO 795) in Oceano for 2000 to present The locations of the two stations are shown in Figure 6, on page 21. In recent years, it was noted that the CIMIS Nipomo station may have been recording irrigation overspray as precipitation and the precipitation data from the station may not be reliable. However, the evapotranspiration data are still considered reliable. For this reason and because the DRI station was discontinued in 2017, the County-operated gauge (No. SLO 795) is the sole source of precipitation data used in this 2024 Annual Report. Figure 5, on page 20, is a composite graph combining data from the DRI and County stations and illustrating annual rainfall totals from available data from 1950 through 2024 (on a calendar-year basis). The average annual rainfall for the NCMA is approximately 15.6 inches.

Monthly rainfall and evapotranspiration (ET) for 2024 as well as average monthly historical rainfall and ET are presented in Figure 7, on page 22. During 2024, below-average rainfall occurred for 8 months and above- average rainfall occurred during the other 4 months. The total for the year was 15.42 inches, just below the average annual rainfall for the area.
12 Tri-Cities Mesa is an upland physiographic feature covering approximately four square miles. It is a remnant of the deposition that was laid down, historically, by Pismo and Arroyo Grande Creeks. Older sand dunes now cover the area (DWR, 1970).
13 The Desert Research Institute (DRI) Western Regional Climate Center Pismo Station (Coop ID: 046943) was discontinued in August of 2017.

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21 FIGURE 7. MONTHLY AND AVERAGE PRECIPITATION AND EVAPOTRANSPIRATION Northern Cities Management Area
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Figure 5, on page 20, illustrates annual rainfall and shows several multi-year drought cycles (e.g., 6 years, 1984 through 1990) followed by cycles of above-average rainfall (e.g., 7 years, 1991 through 1998). Except for 2010, the period from 2007 through 2015 (8 years) experienced below-average annual rainfall, indicating a dry hydrologic period. This pattern continued into late 2016 when the hydrologic pattern appeared to have broken the serious drought that the area (and state) had experienced for the previous 5 years. Annual rainfall totals between 2016 and 2019 were normal fluctuations between wet and dry years. However, between 2019 and 2022, there was a return to drought conditions. The above-average rainfall received in 2023 and the average rainfall received in 2024 have resulted in a return to normal conditions, as illustrated in Figure 5, on page 20.

2.3 Evapotranspiration
CIMIS maintains weather stations in locations throughout the state to provide real-time wind speed, humidity, and evapotranspiration data. The nearest CIMIS station to the NCMA is the Nipomo station (see Figure 6, on page 21). The Nipomo station has gathered data since 2006. While this station may have been subject to irrigation overspray in recent years (noted in Section 2.2), this does not have a significant impact on the measurements used for calculating ET. The monthly ET data for the Nipomo station is shown in Figure 7, on page 22, for 2024 and average conditions (over 10 years). The ET rate affects the recharge potential of rainfall and the amount of outdoor water use (irrigation).

2.4 Geology and Hydrogeology
The current understanding of the geologic framework and hydrogeologic setting is based on numerous previous investigations, particularly Woodring and Bramlette (1950), Worts (1951), Miller and Evenson (1966), DWR (1970, 1979, and 2002), Fugro (2015), Geoscience Support Services (2019 and 2021), and Ramboll (2022).

The NCMA overlies the northwest portion of the SMRVGB. There are two principal aquifers in the NCMA portion of the SMRVGB. Groundwater pumped from the sedimentary deposits that make up the main municipal production aquifer underlying the NCMA is derived from the Paso Robles Formation 14 and the underlying Careaga Sand.15 The Paso Robles Formation and Careaga Sand aquifers together are referred to as the deep aquifer system in this report. All municipal pumping in the NCMA occurs on the Tri-Cities Mesa and is produced from the deep aquifer.

The second principal aquifer is the alluvial aquifer, consisting of Quaternary-age alluvial sediments of Arroyo Grande Creek, Los Berros Creek, and the Cienega Valley. Most agricultural groundwater production in the Cienega Valley is presumed to be extracted from a lower, confined to semi-confined portion of the alluvial aquifer (DWR, 1970).

Several faults either cross or form the boundary of the NCMA, as identified by DWR (2002), Pacific Gas & Electric (PG&E) (PG&E, 2014), and others. The Oceano Fault (USGS, 2006) trends northwest-southeast across the central portion of NCMA and has been extensively studied by PG&E (2014). Offshore, the Oceano Fault 14 The Plio-Pleistocene-age Paso Robles Formation aquifer consists of unconsolidated deposits ranging from fine to coarse sand and gravel, silty to clayey sand and gravel, and fine to medium silty sand. Regionally, the formation is compartmentalized into two to five aquifers zones designated from top to bottom as the A to E Zones. These aquifer zones are separated by silt and clay confining beds near the coast and are generally merged inland (DWR, 1970). 15 The Pliocene-age Careaga Sand consists of unconsolidated to well-cemented calcareous coarse sand with gravel, fine to medium sand, and silty sand. The Careaga Sand is of marine origin (DWR, 1970).

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connects with the Hosgri and Shoreline fault systems several miles west of the coast. Onshore, the Oceano Fault consists of two mapped fault splays, including the main trace of the Oceano Fault as well as the Santa Maria River Fault, which diverges northward of the Oceano Fault through the Cienega Valley before trending into and across the Nipomo Mesa.

It is unknown the extent to which the Oceano and Santa Maria River faults impede groundwater flow within the deep aquifer system materials. However, movement on the faults, as mapped by PG&E (2014), may suggest a possible impediment to flow within the Careaga Sand and possibly the Paso Robles Formation.

PG&E (2014) suggests that the existence of the Santa Maria River Fault is “uncertain.” However, the water elevation contour maps of the NCMA (Figure 8, on page 28, and Figure 9, on page 29) (discussed in more detail in Section 3.1.1) may suggest that the Santa Maria River Fault plays a potential, but unknown, role in groundwater flow across the NCMA.

The Wilmar Avenue Fault generally forms the northern boundary of the NCMA, apparently acting as a barrier to groundwater flow from the older consolidated materials north of the fault southward into the SMRVGB.

There is no evidence, however, that the Wilmar Avenue Fault impedes alluvial flow in the Pismo Creek, Meadow Creek, or Arroyo Grande Creek alluvial valleys.

2.5 Groundwater Flow and Recharge
The groundwater system of the NCMA has several sources of recharge, including precipitation, agricultural return flow, seepage from stream flow, and subsurface inflow from adjacent areas. Precipitation-driven recharge is enhanced by several stormwater retention ponds in NCMA.16 According to the DWR Bulletin 63-3 report (DWR, 1970), both the Paso Robles Formation aquifer and the lower confined portion of the Cienega Valley alluvial aquifer are recharged primarily from subsurface groundwater inflow from the east, where the overlying confining layers are thin to nonexistent (DWR, 1970). These recharge areas to the east include inland reaches of Arroyo Grande Valley and portions of Nipomo Mesa (DWR, 1970). Groundwater quality data presented in DWR Bulletin 63-3 (DWR, 1970) and corroborated with data available through the Central Coast Regional Water Quality Control Board Irrigated Lands Regulatory Program show evidence of recharge to the alluvial aquifer of the Cienega Valley from the Paso Robles Formation aquifer on the Nipomo Mesa. However, this recharge mechanism appears to be slowing because of declining water levels on the Nipomo Mesa, as documented in recent NMMA annual reports (see Section 6.1.1).

The deep aquifer system is also recharged to a lesser extent by the percolation of direct precipitation and agricultural return flow on the Tri-Cities Mesa (DWR, 1970). In addition, some return flows occur from imported surface supply sources, including Lopez Lake and the California State Water Project (SWP). Discharge in the region is dominated by groundwater production from pumping wells and minor discharge through phreatophyte 17 consumption. Historically, hydraulic gradients show that subsurface outflow discharge occurs westward from the groundwater basin to the ocean, as indicated by historical groundwater elevations observed in wells throughout the NCMA. This subsurface outflow is an important control to limit the potential of seawater intrusion. This westward gradient and direction of groundwater flow is still prevalent throughout the northern 16 Within their jurisdictions, Arroyo Grande and Grover Beach each maintain stormwater retention ponds; the SLOFCWCD maintains the stormwater system, including retention ponds, in OCSD. These ponds collect stormwater runoff, allowing the runoff to recharge the underlying aquifers.
17 A phreatophyte is a deep-rooted plant that obtains a significant portion of the water that it needs from the water table.

Phreatophytes are plants that are supplied with surface water or the upper portion of the near-surface water table and often have their roots constantly in touch with moisture.

FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 25
portion of NCMA, although there is evidence that the westward gradient may have reversed in recent years in the area south of Cienega Valley.

The following descriptions of the boundary conditions of the NCMA are derived primarily from Todd (2007).

The eastern boundary is coincident with the SLOFCWCD Zone 3 management boundary and with the northwestern boundary of the NMMA. Aquifer materials of similar formation, provenance, and characteristics are present across most of this boundary, which allows subsurface flow to occur between the NCMA and NMMA.

The northern and northwestern boundary, established by the Court during the 2005 Stipulation, is coincident with the Wilmar Avenue Fault, which is located approximately along Highway 101 from Pismo Creek to the southeastern edge of the Arroyo Grande Valley. There is likely insignificant subsurface flow from the consolidated materials (primarily Pismo Formation) north of the Wilmar Avenue Fault across the boundary into the NCMA; however, basin inflow occurs within the underflow associated with alluvial valleys of Arroyo Grande and Pismo creeks.

The southern boundary of the NCMA is an east-west line, roughly located along the trend of Black Lake Canyon and perpendicular to the coastline. Historically, it appears that groundwater flow is typically roughly parallel to the boundary. This suggests that little to no subsurface inflow occurs across this boundary.

The western boundary of the NCMA follows the coastline from Pismo Creek in the north to Black Lake Canyon.

Given the generally westward groundwater gradient in the area, this boundary is the site of subsurface outflow and is a primary impediment to seawater intrusion. However, the boundary is susceptible to seawater intrusion if groundwater elevations onshore decline, such as may be occurring seasonally in the southeast portion of NCMA along the boundary with NMMA.

FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 26
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FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 27
SECTION 3: Groundwater Conditions

3.1 Groundwater Levels
Groundwater elevation data are gathered from the network of wells throughout the NCMA to monitor the effects of groundwater use and recharge, and to monitor the threat of seawater intrusion. Over time, analysis of these groundwater elevation data has included the development of groundwater elevation contour maps, hydrographs, and an evaluation of key sentry well water elevations. The historical groundwater elevation data are provided in Appendix A.

3.1.1 Groundwater Level Contour Maps
Contoured groundwater elevations for the spring (April 2024) and fall (October 2024) monitoring events, are presented in Figure 8, on page 28, and Figure 9, on page 29, respectively. From an increased understanding of the groundwater basin aquifer system and to be consistent with recent work completed for the Phase 1B model, the groundwater elevation analysis was performed separately for each of the two principal aquifers. As described earlier (see Section 2.4), the two principal aquifers are the deep aquifer (consisting of the Paso Robles Formation and the Careaga Sand) from which all municipal production is pumped, and the alluvial aquifer within the Cienega Valley, from which most agricultural production is pumped.

Groundwater level contours for April 2024 are presented in Figure 8, on page 28. Spring groundwater elevation contours in the deep aquifer system north of the Santa Maria River Fault (displayed using blue lines) show a westerly to southwesterly groundwater flow. The groundwater gradient and flow in the deep aquifer system in the southern portion of the NCMA are generally inferred based on historical records, historical trends, and water level data from the NMMA farther east. This is a result of the limited number of wells and water level data in the southernmost portion of the NCMA, which is dominated by sensitive-species dunes and California State Parks land. April 2024 groundwater elevations in the deep aquifer system main production zone along the coast ranged from 11.3 to 18.1 feet (NAVD 88). Pumping effects are noted in the areas of concentrated municipal pumping on Tri-Cities Mesa.

Spring groundwater contours in the alluvial aquifer (displayed using yellow lines) exhibit a gradient and flow direction that generally follows the alignment of Arroyo Grande Creek (Figure 8, on page 28).

Groundwater elevation contours for October 2024 are presented in Figure 9, on page 29. Fall groundwater contours in the deep aquifer system north of the Santa Maria River Fault show a generally west-to- southwesterly groundwater flow, similar to conditions in the spring. Some minor pumping effects are evident in the area of the municipal wells. In contrast to recent years, fall groundwater contours in the alluvial aquifer show only minor pumping effects from agricultural groundwater production (Figure 9, on page 29).

October 2024 groundwater elevations in the deep aquifer system main production zone along the coast ranged from 10.7 to 15.9 feet (NAVD 88).

Agricultural groundwater pumping results in a seasonal drawdown of water levels in the alluvial aquifer in the Cienega Valley south and east of Arroyo Grande Creek. As shown on Figure 8, on page 28, the spring alluvial groundwater elevations in the Cienega Valley range up to more than 40 feet above sea level (NAVD 88) in the upper Cienega Valley, while the fall water levels in this area only extend up to about 30 feet.18 18 Note that 0.0 feet (NAVD 88) is 2.72 feet lower than mean sea level (MSL) and is 0.08 feet above the mean lower low water (MLLW) (which can be thought of as the average height of the lowest tides), as recorded at the Port San Luis tide station datum ( https://tidesandcurrents.noaa.gov/datums.html?id=9412110) .

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FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 30

3.1.2 Historical Water Level Trends
Hydrographs of five wells in the NCMA monitoring network are presented in Figure 10, on page 31. Two of the wells are completed in the deep aquifer system (32D03 and 32D11) and three of the wells are completed in the alluvial aquifer within the Cienega Valley (28K02, 30K03, and 33K03). As of fall 2024, 33K03 has been destroyed.

The hydrographs for wells 32D03 and 32D11 (Figure 10, on page 31) are paired hydrographs for deep aquifer system wells in the vicinity of the municipal wellfields. Depending on the duration of pumping of the municipal wells, water levels in these wells historically have been below the levels of wells in other areas of the NCMA for prolonged periods. The hydrographs show that, historically, groundwater elevations in these wells generally have been above 0.0 feet (NAVD 88). From 2007 to 2009, an area of lower groundwater elevations (a trough) beneath the active wellfield appeared. Groundwater pumping was at its peak from 2007 to 2009 (in comparison with the pumping of the last 15 years) and contributed to the apparent seawater intrusion event in the coastal wells in 2009.

As illustrated in Figure 10, on page 31, the water elevations of all the wells, including the paired deep aquifer system wells 32D03 and 32D11, exhibited a steady decline from 2011 to 2016, during which time rainfall was below normal every year. In this period, groundwater elevations declined to near 0.0 feet (NAVD 88) or, in the case of alluvial aquifer well 33K03, to below 0.0 feet (NAVD 88). By October 2016, the groundwater elevations in these wells were generally below the levels observed in 2009–2010.

In 2016 and 2017, these five wells each exhibited an overall increase in water levels (with the exception of the normal, seasonal decline during the summer), generally reaching similar water levels as observed in 2011.

In 2017, water levels returned to a generally declining trend in all the wells. This trend continued through 2022, until 2023 when water levels rebounded rapidly in response to the wet winter of 2022/2023. In 2024, water levels remain elevated, with most wells showing a slight increase in spring water levels.

3.1.3 Sentry Wells and the Deep Well Index
Regular monitoring of water elevations in clustered sentry wells located along the coast is an essential tool for tracking groundwater elevation changes at the coast. Groundwater elevations in these wells are monitored quarterly as part of the sentry well monitoring program. As shown by the hydrographs for the five sentry well clusters (Figure 11, on page 32), the sentry wells provide a long period of record of groundwater elevations.

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60 P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 10 NCMA Selected Hydrographs Well 32D03
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NAVD88 - North American Vertical Datum of 1988
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FIGURE 10. SELECTED HYDROGRAPHS
Northern Cities Management Area
San Luis Obispo County, California
31 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 0 5
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 11 NCMA Sentry Well Hydrographs Well 24B03
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Highway 1
Pier Avenue
Oceano Dunes
Well 30F03
Well 30F02
Well 30N02
Well 30N03
Well 36L01
Well 36L02
Flowing Artesian
Flowing Artesian
Flowing Artesian
Notes:

NAVD88 - North American Vertical Datum of 1988
FIGURE 11. SENTRY WELL HYDROGRAPHS
Northern Cities Management Area
San Luis Obispo County, California
32 FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 33
An inspection of the recent data shown in Figure 11, on page 32, compared with the historical record, illustrates some noteworthy trends:
From 2013 until near the end of 2016, the water level trend of well 30N02 (Pier Avenue)—one of the wells that experienced elevated total dissolved solids (TDS) and chloride levels (i.e., water quality degradation) in 2009–2010—looked similar to the water level trend of the well in 2007–2010, immediately before and during the period of incipient seawater intrusion. Then, between 2016 and 2020, the downward trend reversed with water elevations seasonally fluctuating around 8 feet above 0.0 feet (NAVD 88). In 2021, water elevations again began trending downward, reaching a maximum depth in fall 2022 at levels similar to the two previous low points before rising rapidly in 2023. Water elevations continued to increase in 2024.
Groundwater levels declined from 2005 to 2016 in the Oceano Dunes wells (36L01 and 36L02), particularly in well 36L01, which is screened across the Paso Robles Formation. Between the end of 2016 and continuing through 2020, both wells had recovered to higher levels. Similar to well 30N02, water elevations in the Oceano Dunes wells returned to a downward trend until both wells reached historically low water elevations in fall 2022. Since fall 2022, water levels have rebounded rapidly in response to the wet winter of 2022/2023. Water elevations have continued to increase in 2024.

The deepest wells in the clusters, 24B03, 30F03, and 30N02, were previously identified as critical wells to monitor for potential seawater intrusion and are included to reflect the net effect of changing groundwater recharge and discharge conditions in the primary production zone of the deep aquifer system. One of the thresholds to track the status and apparent health of the aquifer is to average the groundwater elevations from these three deep sentry wells to generate a single, representative index, called the Deep Well Index.

Previous studies suggested a Deep Well Index value of 7.5 feet above 0.0 feet (NAVD 88) as a minimum threshold below which the aquifer is at risk for eastward migration of seawater and a subsequent threat of seawater intrusion. The historical variation of the Deep Well Index is presented in Figure 12, on page 34.

Inspection of the Deep Well Index in 2008–2009, before the period of water quality degradation in wells 30N03 and 30N02, shows that the Deep Well Index dropped below the 7.5-foot threshold and remained below that level for almost 2 years. Since the start of the drought in 2011, the Deep Well Index dropped below the threshold several times, but usually for only a few months at a time.

In 2024, the Deep Well Index started the year above the trigger value with an index value of 12.3 feet in January. The index value continued to climb through early April, peaking at 13.8 feet, and then generally declined throughout the rest of the year, finishing the year at about 11.51 feet (NAVD 88) (October 2024) (Figure 12, on page 34).

Key wells—including 24B03, 30F03, 30N02, 36L01, 36L02, and 32C03—are instrumented with pressure transducers equipped with specific conductivity (conductivity) probes that periodically record water level, water temperature, and conductivity (Figures 13 through 18, on pages 35 through 40). Occasional transducer malfunctions have resulted in variable conductivity data in some of the wells during certain years, including 2015 and 2019. Malfunctioning transducers have been replaced and continue to be monitored in an ongoing effort to maintain a properly functioning monitoring network. A key technological upgrade accomplished in 2022 was the addition of telemetry to the pressure transducers installed in the Deep Well Index wells (24B03, 30F03, and 30N02). This upgrade provides real-time monitoring of the Deep Well Index, allowing for informed, timely decision-making regarding the management of NCMA groundwater resources.

P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 12 Hydrograph of Deep Well Index Level_with Approximate DWI data_v2 Notes:

NAVD88 - North American Vertical Datum of 1988
mg/L - milligrams per liter
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FIGURE 12. HYDROGRAPH OF DEEP WELL INDEX ELEVATION
Northern Cities Management Area
San Luis Obispo County, California
34 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 -5-4-3-2-101234567891011121314151617181920
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 13 NCMA Well 24B03 Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
Data gap due to accidental removal of transducers by SLO Co.

FIGURE 13. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 24B03 Northern Cities Management Area
San Luis Obispo County, California
35 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 -5-4-3-2-101234567891011121314151617181920
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Highway 1 Deep Well
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 14 NCMA Well 30F03 Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
Data gap due to accidental removal of transducers by SLO Co.

FIGURE 14. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 30F03 Northern Cities Management Area
San Luis Obispo County, California
36 -5-4-3-2-101234567891011121314151617181920
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Pier Avenue Deep Well
Well Depth: 255 feet (Paso Robles Formation)
Deep Well Index
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 15 NCMA Well 30N02 Deep Well Index
Threshold: 7.5 feet
Sensor malfunction. Field
measurements indicate that
specific conductivity is stable
Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
Data gap due to accidental removal of transducers by SLO Co.

FIGURE 15. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 30N02 Northern Cities Management Area
San Luis Obispo County, California
37 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 -5-4-3-2-101234567891011121314151617181920
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Oceano Dunes Deep Well
Well Depth: 237 feet (Paso Robles Formation)
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 16 NCMA Well 36L01 Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
FIGURE 16. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 36L01 Northern Cities Management Area
San Luis Obispo County, California
38 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 -5-4-3-2-101234567891011121314151617181920
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Oceano Dunes Deep Well
Well Depth: 545 feet (Careaga Sand)
Well 36L02 Manual Measurements
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 17 NCMA Well 36L02 Transducer data corrupted
Dashed where inferred
Sensor malfunction. Field measurements indicate that specific conductivity is stable Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
FIGURE 17. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 36L02 Northern Cities Management Area
San Luis Obispo County, California
39 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 -4
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P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 18 NCMA Well 32C03 Notes:

NAVD88 - North American Vertical Datum of 1988
uS/cm - microsiemens per centimeter
FIGURE 18. WATER ELEVATION, CONDUCTIVITY, AND TEMPERATURE, WELL 32C03 Northern Cities Management Area
San Luis Obispo County, California
40 FINAL | Northern Cities Management Area
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Wells 24B03, 30F03, and 30N02 comprise the wells used to calculate the Deep Well Index. Wells 36L01 and 36L02 are adjacent to the coast. Well 32C03 is the easternmost well and is adjacent to the boundary between the NCMA and NMMA. The following discusses 2024 water levels for these key wells:
Deep Well Index Wells: Water levels in the Deep Well Index wells increased throughout the early part of 2024 in response to above-average precipitation received during the first quarter. Water levels peaked in wells 24B03, 30F03, and 30N02 in early to mid-April. The water levels in wells 24B03, 30F03, and 30N02 then declined slightly until early September, when they began to rise.

Consistent with patterns seen in previous years is the variability of aquifer response among the three wells.

Well 24B03, the northernmost well located in the North Beach Campground, maintains a relatively stable and moderated water level throughout the year and consistently sustains groundwater elevations higher than the Deep Well Index value (Figure 13, on page 35). The water level in 24B03 mitigates the water levels in 30N02, which typically maintain levels consistently deeper than the Deep Well Index. Well 30F03 generally closely follows the Deep Well Index value.
Coastal Wells: The groundwater elevation in well 36L01, screened within the Paso Robles Formation, remained within 7.0 (July 2024) to 9.1 (January 2024) feet above 0.0 feet (NAVD 88) throughout 2024.

These levels are within the historical range; however, they have increased since 2023 due to the wet winter during 2022/2023 and above-average precipitation during the first quarter of 2024. The water level in well 36L02, which is screened within the Careaga Sand, illustrates a much greater seasonal fluctuation than is observed in 36L01. The water elevation in 36L02 ranged from 16.8 feet in April to approximately

9.9 feet (NAVD 88) in October.
NCMA/NMMA Boundary: The groundwater elevation in 2024 continued to trend upward compared to water levels reported in 2023. In 2024, the groundwater elevation in well 32C03 ranged from 12.8 feet (October 2024) to 23.0 feet (April 2024) above 0.0 NAVD 88. This is a turnaround from the below 0.0 feet (NAVD 88) seasonal low levels experienced in 2021 and 2022. The 2024 seasonal high-water level in well 32C03 is the highest seen since 2012.

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3.2 Change in Groundwater in Storage
The relative change of groundwater levels and the associated change in groundwater in storage in the NCMA portion of the SMRVGB between April 2023 and April 2024 were estimated using a comparison of water level contour maps created for these periods. Separate estimates of change in groundwater in storage were computed for both the deep aquifer system and the alluvial aquifer and then summed together to represent the total NCMA estimated change in groundwater in storage. The comparison of the April water levels was chosen to comply with DWR reporting requirements and SGMA.

For each aquifer, the groundwater contour lines from each period were compared, and the volumetric difference between the two periods was calculated. The same selection of deep aquifer and alluvial aquifer wells was used to calculate the volumetric difference for both periods. The change of groundwater elevations for the deep aquifer is presented in Figure 19, on page 43, and for the alluvial aquifer in Figure 20, on page

44.Figure 19, on page 43, illustrates that water elevations in the deep aquifer system generally increased across most of NCMA. The most significant increases occurred along the southeastern boundary near NMMA and the northwestern coastal area. However, water elevations declined in the north-central portion of NCMA.

Overall, there was a positive net change in groundwater storage in the deep aquifer. Figure 20, on page 44, shows that increases in alluvial aquifer water elevations occurred throughout a majority of the Cienega Valley, with the largest increases occurring in the areas of inflow from Arroyo Grande Creek and Los Berros Creek.

Water elevations declined in the outflow area from Arroyo Grande and Los Berros Creeks. Overall, there was a positive net change in groundwater storage in the alluvial aquifer.

From the change of water levels maps, a volumetric change in groundwater in storage estimate was made for each aquifer, based on assumed aquifer properties,19 and then summed to represent the total NCMA estimated change in groundwater in storage. The net changes in groundwater levels in both aquifers represent a net increase of groundwater in storage from April 2023 to April 2024 of approximately 530 AF (compared to a net increase of 3,609 AF during the previous year).
19 A storage coefficient of 0.02 was used for the deep aquifer system. This is representative of the Paso Robles Formation and Careaga Sand in the area, as documented in the SMRVGB Characterization Project (Fugro, 2015).

A specific yield value for the alluvial aquifer of 0.09 was back-calculated using the 2019 estimated change in alluvial groundwater in storage represented by the calculated agricultural demand (see Section 4.2.1) and an alluvial groundwater elevation change map representing the total volume change that occurred between April 2019 and October 2019.

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44 FINAL | Northern Cities Management Area
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3.3 Water Quality
Water is used in several ways in the NCMA, and each use requires a certain minimum water quality. Because contaminants from seawater intrusion or anthropogenic sources can potentially impact the quality of water in the aquifer, water quality is monitored at each of the sentry well locations in the NCMA and County Monitoring Well No. 3 (32C03).

3.3.1 Quarterly Groundwater Monitoring
Quarterly groundwater monitoring events occurred in January, April, July, and October 2024. During each event, depths to groundwater were measured, and wells were sampled using procedures, sampling equipment, and in-field sample preservation protocol pursuant to ASTM International Standard D4448-01.

The water quality data from these events and historical data from these wells are provided in Appendix A.

Graphs of historical chloride and TDS concentrations over time are presented in Figure 21, on page 46, and Figure 22, on page 47, respectively, to monitor for trends that may aid in the detection of impending seawater intrusion.

The historical water quality data show that concentration levels of chlorides and TDS, as well as other constituents, have remained relatively stable within a narrow historical range since 2009. Improved management of municipal groundwater use, because of an overall reduction in pumping since 2009, has likely contributed to the past several years of relatively stable groundwater quality.

In the first quarter of 2022 water quality results in OCSD MW-Yellow exhibited a change of water quality type when compared to historical records. As a result of the unusual Q1 water quality results in OCSD MW-Yellow, the well was resampled in February 2022. Results from the re-sample analysis confirm the Q1 shift in water quality in OCSD MW-Yellow. Considering the nearly identical water quality results between the OCSD MW- Yellow and MW-Blue wells, it was concluded that the well casing in the MW-Yellow completion has become compromised and open to the formation within a similar strata as the MW-Blue perforated interval (~190 to 265 feet below ground surface [bgs]). Therefore, the MW-Yellow well completion is no longer considered representative of the 625 to 645 feet below-ground surface interval of the Careaga Sand (see Figure 4, on

Page 16 ends

Yellow was sounded to its full depth of completion (645 feet), indicating that the well casing had not fully collapsed at that time. Well abandonment for the MW-Yellow completion will be considered by the TG.

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FIGURE 21. CHLORIDE CONCENTRATIONS IN MONITORING WELLS
Northern Cities Management Area
San Luis Obispo County, California
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FIGURE 22. TOTAL DISSOLVED SOLIDS CONCENTRATIONS IN MONITORING WELLS Northern Cities Management Area
San Luis Obispo County, California
47 FINAL | Northern Cities Management Area
2024 Annual Monitoring Report
GSI Water Solutions, Inc. 48

3.3.2 Analytical Results Summary
Analytical results of key water quality data, including chloride, TDS, and sodium, were generally consistent with historical concentrations and observed ranges of constituent concentrations during 2024. Although some monitoring wells reported constituents above the California DDW secondary maximum contaminant limit for TDS and/or sulfate (36L01, 30F02, and 30N02), no water quality results indicate seawater intrusion.

Figure 23A through D, beginning on page 50, are a set of Piper diagrams representing groundwater sampling results from each of the quarterly sampling events in 2024. The Piper diagram provides a means of presenting the relative abundance of common ions (cations and anions) in each water quality sample. The relative abundance of common ions in each water quality sample, including cations- sodium, calcium, magnesium, and potassium, and anions- bicarbonate, chloride, and sulfate- determine the ‘water quality type’ of the sample. Examples of different water quality types include ‘calcium-magnesium-sulfate’ type (i.e., 30N02 and 36L01), ‘sodium-chloride’ type (i.e., 32C03), and ‘calcium-bicarbonate’ type (all remaining monitored wells).

The Piper diagrams (Figure 23A through 23D, beginning on page 50) show the quarterly 2024 water quality results, which generally fall into these three water quality type groupings. The relative abundance of common ions found in seawater is presented as a red “X” on the Piper diagrams for reference purposes. Well 32C03 generally demonstrates the most similar signature to seawater; however, the TDS present in 32C03 are more than two orders of magnitude lower than that of seawater.20 In the event of possible future incipient seawater intrusion, migration towards the seawater base (red “X”) would be expected for the affected well(s) on the Piper diagram.

Three separate water quality types are found in the monitoring wells:

1.The Pier Avenue deep well (30N02), screened in the Paso Robles Formation from 175 to 255 feet bgs, and Oceano Dunes intermediate well (36L01), screened in the Paso Robles Formation from 227 to 237 feet bgs, are screened in the same production zone. This is despite their different nomenclature as “deep” compared with “intermediate” wells. Relative to the other wells in the area, these two wells are high in sulfates and have calcium-magnesium-sulfate-rich water. Both wells are relatively low in chloride. This is significant because this zone, and well 30N02, was the site of an apparent seawater intrusion event characterized by a rapid increase in chloride concentrations in 2009–2010.

2.The County Monitoring Well No. 3 (32C03), screened from 90 to 170 feet bgs, in the Paso Robles Formation, has an apparent water quality that is different than any of the other wells in the area. It is relatively high in sodium, chloride, and potassium. Its location in the right quadrant of the diamond- shaped part of the Piper diagram (Figure 23A through 23D, beginning on page 50) commonly characterizes a sodium-chloride-rich groundwater representative of marine or deep ancient groundwater, even though it is a relatively shallow well and screened within the Paso Robles Formation, a Plio-Pleistocene-age alluvial deposit.

3.All of the other wells in the monitoring network fall into the third category of groundwater water quality.

These wells are all generally calcium-bicarbonate groundwater that is commonly associated with shallow groundwater. This grouping of water quality represents groundwater from wells that are screened in both the Paso Robles Formation and the Careaga Sand (wells 24B03, 30F03, and 36L02 are screened in the Careaga Sand; the others are screened in the Paso Robles Formation). 20 The concentration of TDS in well 32C03 is generally the lowest out of all 16 historically monitored wells in NCMA.

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None of the water quality results from monitoring wells throughout 2024 indicate an incipient episode or immediate threat of seawater intrusion. There has been no water quality results indicative of seawater intrusion since the decline of TDS, sodium, and chloride concentrations detected in Paso Robles Formation wells 30N02, 30N03, and OCSD MW-Blue following the 2009–2010 seasons. No indications of seawater intrusion have been observed in wells screened in the underlying Careaga Sand. At this time, without additional offshore data, the precise location of the interface or mixing zone is not known and will not be known unless and until it intercepts a monitoring well. However, the airborne electromagnetic survey conducted in 2020 (Ramboll, 2022) indicates that no seawater intrusion was occurring in the deep aquifer system at the time of the survey and that the interface generally conformed to the Ghyben-Herzberg ratio.21 A second airborne electromagnetic survey was conducted in November 2023. The data from this survey became available in the fourth quarter of 2024. It has not yet been reviewed by the TG. 21 Under normal conditions, the higher density of saltwater causes it to move into coastal aquifers in a wedge shape under the freshwater. The shape of the saltwater wedge is described by the Ghyben–Herzberg ratio which states that, for every foot of fresh water in an unconfined aquifer above sea level, there will be forty feet of fresh water in the aquifer below sea level (Ploessel, 1982).

FIGURE 23A.

PIPER DIAGRAMS OF WATER QUALITY IN SELECT MONITORING WELLS - 2024 Q1 RESULTS Northern Cities Management Area
San Luis Obispo County, California
50 FIGURE 23B.

PIPER DIAGRAMS OF WATER QUALITY IN SELECT MONITORING WELLS - 2024 Q2 RESULTS Northern Cities Management Area
San Luis Obispo County, California
51 FIGURE 23C.

PIPER DIAGRAMS OF WATER QUALITY IN SELECT MONITORING WELLS - 2024 Q3 RESULTS Northern Cities Management Area
San Luis Obispo County, California
52 FIGURE 23D.

PIPER DIAGRAMS OF WATER QUALITY IN SELECT MONITORING WELLS - 2024 Q4 RESULTS Northern Cities Management Area
San Luis Obispo County, California
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SECTION 4: Water Supply and Production/Delivery

4.1 Water Supply
The NCMA water supply consists of three major sources: Lopez Lake, the SWP, and groundwater. Each source of supply has a defined delivery volume that varies from year to year.

4.1.1 Lopez Lake
The Lopez Project consists of Lopez Lake, Lopez Dam, Lopez Terminal Reservoir, and Lopez Water Treatment Plant and is operated by SLOFCWCD Zone 3. SLOFCWCD Zone 3 provides treated water directly to the Zone 3 agencies and releases water to Arroyo Grande Creek for habitat conservation and agricultural use. The Zone 3 agencies include Arroyo Grande, Grover Beach, Pismo Beach, OCSD, and CSA 12, which serves Avila Beach and is not in the NCMA.

The operational safe yield of Lopez Lake is 8,730 AFY, which reflects the amount of sustainable water supply.

Of this, 4,530 AFY is apportioned to the agencies, and 4,200 AFY is reserved for downstream releases to maintain flows in Arroyo Grande Creek and provide groundwater recharge. Contract changes that went into effect at the end of October 2022 allow Zone 3 agencies to store unused entitlement water and downstream release water in the reservoir for later use (see further details below). The 2024 SLOFCWCD Zone 3 entitlements are shown in Table 2.

Table 2. Lopez Lake (SLOFCWCD Zone 3 Contractors) Water Entitlements (AFY) Contractor
Contract Water
Entitlement
(AFY)
Percent of Total
Arroyo Grande 2,290 50.55%
Grover Beach 800 17.66%
Pismo Beach 892 19.69%
OCSD 303 6.69%
CSA 12 (not in NCMA) 245 5.41%
Total 4,530 100%
Downstream Releases 4,200 —
Safe Yield of Lopez Lake 8,730 —
Notes
— = not applicable AFY = acre-feet per year CSA = County Service Area NCMA = Norther Cities Management Area OCSD = Oceano Community Services District SLOFCWCD = County of San Luis Obispo Flood Control & Water Conservation District In December 2014, SLOFCWCD Zone 3 adopted the Low Reservoir Response Plan (LRRP) (SLOFCWCD, 2014).

The LRRP establishes actions that SLOFCWCD Zone 3 can take when the amount of water in storage in the reservoir drops below 20,000 AF, provided that the SLOFCWCD Board of Supervisors declares a drought emergency. The purpose of the LRRP is to limit downstream releases and municipal diversions from Lopez Lake to preserve water within the reservoir, above the minimum pool, for a minimum of 3 to 4 years under drought conditions.

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The reduction strategies for the LRRP are tied to the amount of water in the reservoir. As the amount of water in the reservoir drops below the triggers (20,000; 15,000; 10,000; 5,000; and 4,000 AF), the hydrologic conditions are reviewed, and adaptive management is used to meet the LRRP objectives. The municipal diversions are to be reduced according to the strategies shown in Table 3.

Table 3. Lopez Lake Municipal Diversion LRRP Reduction Strategy Amount of Water
in Storage (AF)
Municipal Diversion
Reduction AFY
20,000 0% 4,530
15,000 10% 4,077
10,000 20% 3,624
5,000 35% 2,941
4,000 100% 0
Notes
AF= acre-feet AFY = acre-feet per year LRRP = Low Reservoir Response Plan The initial prescribed actions after the LRRP is enacted include (1) reductions in entitlement water deliveries; (2) reductions in downstream releases; (3) no new allocations of surplus water from unreleased downstream releases; and (4) extension of time that agencies can take delivery of existing unused water throughout the duration of the drought emergency, subject to evaporation losses if the water is not used in the year of original allocation. Included in the LRRP is an adaptive management provision that allows the initial prescribed actions to be modified and adapted to specific drought conditions.

The initial prescribed actions concerning downstream releases are that they should be reduced according to the strategies described in Table 4. The release strategies represent the maximum amount of water that can be released. The SLOFCWCD Zone 3 controls the timing of the reduced releases to meet the needs of the agricultural stakeholders and to address environmental requirements.

Table 4. Lopez Lake Downstream Release LRRP Reduction Strategy Amount of Water
in Storage (AF)
Downstream Release
Reduction AFY
20,000 9.5% 3,800
15,000 9.5% 3,800
10,000 75.6% 1,026
5,000 92.9% 300
4,000 100% 0
Notes
AF= acre-feet AFY = acre-feet per year LRRP = Low Reservoir Response Plan

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The LRRP was put into effect on April 1, 2015. Throughout 2015 and all of 2016, SLOFCWCD Zone 3 operated Lopez Lake pursuant to the 15,000 AF diversion reduction trigger that required a 10 percent reduction in municipal diversions. The 10,000 AF trigger requiring a 20 percent reduction was avoided in 2016 because the agencies enacted mandatory water conservation measures and voluntarily reduced municipal diversions from Lopez Lake by 20 percent. Lopez Lake recovered from a low of 11,000 AF in storage to a peak of more than 30,000 AF in May 2017, ending with approximately 25,000 AF at the start of 2018 because of the relatively heavy rainfall year of late 2016 and early 2017. Although contractually the LRRP is no longer in effect when both triggers are rescinded (i.e., the Board of Supervisors declaration of water emergency and reduction of reservoir levels to below 20,000 AF), the SLOFCWCD Zone 3 agencies resolved to keep the LRRP in effect. Because the reservoir volume was above 20,000 AF, no mandatory reductions in municipal deliveries were required in 2017, 2018, or 2019. In 2020, the reservoir storage level stayed above 20,000 AF until December, when it reached a level of 19,826 AF. The LRRP was not activated during 2020.

In 2021, the highest reservoir storage level occurred in January, at 19,874 AF. The reservoir storage level declined throughout most of 2021, reaching a low point of 14,174 AF in November. With the declining reservoir storage approaching the 15,000 AF trigger level, the Board of Supervisors voted on August 24, 2021, to enact the LRRP, and the initial prescribed action of a 10 percent municipal entitlement reduction (retroactive to April 2021) was put in place. The year 2021 ended with reservoir storage at just less than 15,000 AF. On July 21, 2022, the Zone 3 Advisory Committee endorsed a 20 percent municipal entitlement reduction (retroactive to April 2022) in anticipation of reaching the 10,000 AF trigger of the LRRP. Throughout 2022, reservoir levels continued to drop until they reached a low point of 10,837 AF on December 10, 2022. Above normal precipitation occurring during the second half of December resulted in reservoir levels recovering to 11,690 AF by the end of 2022. The LRRP remained in effect with 20 percent municipal entitlement reductions through the end of 2022.

As a result of above-average rainfall in January through March 2023, the Lopez Lake storage level rapidly increased to 26,602 AF in January, 30,439 AF in February, and to maximum capacity (49,476 AF) and began spilling in March 2023. The reservoir continued to spill through June 2023, after which reservoir levels slowly began to decline through October, reaching a low of 46,998 AF in storage. On January 19, 2023, the Zone 3 Advisory Committee approved exit from the LRRP and a return to 100 percent Lopez entitlements retroactive to April 1, 2022. The Lopez Lake storage level was 47,365 AF at the end of 2023.

As a result of contract changes that went into effect at the end of October 2022, the Zone 3 agencies are now able to store their unused annual water entitlement and any surplus water they receive in Lopez Reservoir, as well as allow for in-lieu storage of SWP water. In other words, each agency now has a stored water account.

The purpose of these changes is to provide agencies greater flexibility to better manage their water supply portfolios and incentivize the conservation of water during emergencies and droughts. The changes provide the agencies greater flexibility to use their water supplies conjunctively (i.e., to implement a balanced use of surface and groundwater supplies based on hydrologic conditions) and additionally allow agencies to transfer stored Lopez and SWP water amongst themselves to improve water supply availability during drought conditions and water supply resiliency for the region.

Under the new Zone 3 contracts, Surplus water is generated by unused downstream releases from the prior Zone 3 water year (April 1 through the following March 31), and Stored water is generated by unused entitlement water. Unlike Surplus water, Stored water can accrue and be accessed indefinitely as long as the stored quantity does not get lost in a spill. Unused entitlement water is calculated annually at the end of each water year on March 31. When the new contracts were adopted in October 2022, existing surplus water for each agency was converted into Stored water as a one-time deal. However, all the Stored water was lost because of the prolonged spill event that occurred from March through June 2023.

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During a month when the reservoir is spilling, Zone 3 agencies are able to take as much of their proportionate share of the spilled volume as they choose without incurring debit against their contract entitlement amount (each agency’s proportionate share is shown in Table 2). For example, Arroyo Grande’s contracted entitlement share is 50.55 percent, so they get 50.55 percent of the total spilled volume credited toward their usage that month (personal communication with David Spiegel, SLOFCWCD, on January 25, 2024). However, while the reservoir is spilling, contractors also lose any Surplus and Stored water they may have at the same rate.

Storage is calculated on an annual basis at the end of each Lopez water year – specifically on March 31, and water is recorded into storage on April 1. In 2024, the agencies’ calculated unused entitlement for the 2023/2024 water year was 2,532.6 AF, which was transferred into their respective storage accounts on April 1, 2024. However, due to Lopez Lake spilling, the entire Stored water volume was lost. During April 2024, approximately 3,403 AF spilled; therefore, Stored water was reduced to zero. Similarly, by the end of 2024, there was no access to Stored water22.

In December 2024, U.S. District Judge Sherilyn Peace Garnett ordered a preliminary injunction that requires the County to increase downstream releases into Arroyo Grande Creek to operate in accordance with the Endangered Species Act. The County is appealing the ruling and legal proceedings will continue into the year 2025. See Section 6.3.1 for more information regarding the preliminary injunction.

Lopez Lake started the year at 47,365 AF in storage in January 2024. The storage level continued to increase, filling to maximum capacity in February (49,476), and began spilling on February 7, 2024 (SLO Co., 2024).

The reservoir continued to spill through June 16, 2024, after which reservoir levels slowly began to decline through the end of the year, reaching a low of 45,502 AF in storage on December 31, 2024 (SLO Co., 2024).

The total deliveries from Lopez Lake in 2024 was 8,790 AF, of which 4,173 AF were delivered to NCMA contractors, 79 AF were delivered to CSA 12, and 4,538 AF were released downstream to maintain flow in Arroyo Grande Creek (Table 5).

Lopez Lake Surplus and Stored water deliveries to the NCMA agencies were both 0 AF and deliveries of Lopez Lake spill water to NCMA agencies totaled 1,200 AF in 2024 (Table 5). 22 Personal communication with Desiree Bravo, SLOFCWCD, on February 14, 2025).

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Table 5. Lopez Lake Deliveries, 2024
Contractor
Entitlement
Usage
(AF)
Lopez
Stored (AF)
Surplus
Usage
(AF)
Lopez Spill
(AF)
Total Lopez Lake
Water Delivery
(AF)
Arroyo Grande 1,313 0 0 652 1,965
Grover Beach 500 0 0 291 791
Pismo Beach 842 0 0 257 1,099
OCSD 318 0 0 0 318
Total NCMA 2024 Usage 2,973 0 0 1,200 4,173
CSA 12 (not in NCMA) 58 0 0 21 79
Downstream Releases 4,538 — — — 4,538
Total 2024 Lopez Lake
Deliveries 7,569 0 0 1,221 8,790
Notes
— = not applicable AF= acre-feet CSA = County Service Area NCMA = Northern Cities Management Area OCSD = Oceano Community Services District
Source: SLOFCWCD Zone 3 Monthly Operations Reports

4.1.2 State Water Project
Pismo Beach and OCSD have contracts with SLOFCWCD Zone 3 to receive water from the SWP. The SLOFCWCD serves as the SWP contractor and provides imported water to local retailers through the SWP Coastal Branch (Coastal Branch) pipeline. Pismo Beach and OCSD, as subcontractors to SLOFCWCD, have annual contractual water delivery allocations, commonly referred to as Table A water, of 1,240 23 AFY and 750 AFY, respectively (Table 6). In addition to its Table A allocation, Pismo Beach holds 1,240 AFY of additional allocation known as “drought buffer” and OCSD holds an additional allocation of 750 AFY of drought buffer. The additional drought buffer allocation held by the agencies is available to augment the SWP water supply when the SWP annual allocation, i.e., the percentage of SWP water available, is less than 100 percent. The additional allocations also increase each agency’s water held in storage. In any given year, however, the SWP contracts held by Pismo Beach and OCSD are only guaranteed for up to 1,240 AF and 750 AF, respectively.24 On November 15, 2022, the Pismo Beach City Council directed staff to work with the SLOFCWCD to increase the Pismo Beach SWP drought buffer to 3,192 AFY, and in April 2023, the OCSD Board of Directors directed staff to increase the OCSD SWP drought buffer to 1,150 AFY. Both of these drought buffer increases are still pending as of the date of this 2024 Annual Report.

As a result of the recent contract changes, the Zone 3 contractors are now able to store unused allocated SWP water locally in Lopez Reservoir for later use (Stored SWP 25 water). Because there is no direct physical 23 100 AF of this 1,240 AF was previously owned by a private party. However, as of October 2022 the 100 AF has been re-retained by City of Pismo Beach with 20 AF being reserved for the private party. 24 If excess water is available and there is capacity in the pipeline the SWP contracts between SLOFCWCD Zone 3 and Pismo Beach or OCSD do not prevent annual deliveries in excess of 1,240 AF or 750 AF, respectively (personal communication with David Spiegel, SLOFCWCD, on February 3, 2022).
25 Not to be confused with SWP “carryover water” stored in San Luis Reservoir.

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connection between Lopez Reservoir and the SWP, no actual SWP water would physically be in the reservoir.

Rather, the exchange would be an in-lieu exchange that occurs on paper through the water accounting process. In WY 2024, no SWP water was stored for any of the agencies in Table 6.

Table 6. NCMA SWP Table A Allocations, Drought Buffers, Stored Water and 2024 Deliveries Agency
Table A
Allocation
(AFY) 1
Drought
Buffer
(AFY)1
Stored SWP
Water
(AF)
2024
Delivery
(AF)
Arroyo Grande — — — —
Grover Beach — — — —
Pismo Beach 1,240 1,240 0 380
OCSD 750 750 0 281
Total Allocation/Delivery,
AFY 1,990 1,990 0 661
Notes
— = not applicable AF=acre feet AFY= acre-feet per year NCMA = Northern Cities Management Area OCSD = Oceano Community Services District SWP = California State Water Project 1 Assumed District can supply 100% of the requested delivery to meet requests that exceed current DWR allocation. DWR set Table A allocation for subcontractors in 2024 at 40%. However, due to surplus water available for SLOFCWCD, 100% of Table A allocation was available for Pismo Beach and OCSD. The SWP contracts held by Pismo Beach and OCSD are only guaranteed for up to 1,240 AF and 750 AF, respectively. Due to surplus water, the drought buffer was not a factor in the water available for delivery to Pismo Beach and OCSD (personal communication with Wes Thomson, SLOFCWCD, on February 14, 2025).

The SWP annual allocation for all contractors throughout California (including SLOFCWCD, Pismo Beach, and OCSD) for 2024 was initially set on December 1, 2023, at 10 percent of Table A's contractual allocation amounts. The 2024 SWP allocation was then increased to 15 percent on February 21, 2024, again to 30 percent on March 22, 2024, and finally to 40 percent on April 23, 2024. SWP contractors can store undelivered Table A water at the SWP facility in San Luis Reservoir (limitations exist on the amount that can be stored in any one year). This stored water is called “carryover water” and can be delivered in subsequent years, but total annual deliveries cannot exceed their Table A allocation due to capacity restrictions in the Coastal Branch. In addition, carryover water can be lost (or “spilled”) if its storage interferes with the storage of current-year SWP water for project needs. Due to 2023 surplus water available for the District in 2024, 100% of Table A allocation was available for Pismo Beach and OCSD. The SWP contracts for Pismo Beach and OCSD are guaranteed at 1,240 AF and 750 AF, respectively. Due to surplus water, the drought buffer was not a factor in the water available for delivery to Pismo Beach and OCSD.

The SWP supply has the potential to be affected by drought and environmental issues, particularly because of the endangered Delta smelt in the Sacramento-San Joaquin Delta (Delta). However, OCSD and Pismo Beach as well as the other SLOFCWCD subcontractors have not been negatively affected to date by reduced SWP supplies because of the SLOFCWCD’s large amount of unsubscribed Table A allocation which has been used to fulfill subcontractors’ requests, even in dry years. Therefore, even when SWP supplies are decreased, the SLOFCWCD’s unsubscribed allocation and any carryover water in San Luis Reservoir provide a buffer so that contracted volumes to subcontractors such as OCSD and Pismo Beach may still be provided in full. During 2024, Pismo Beach took delivery of 380 AF of SWP water and OCSD took delivery of 281 AF of SWP water.

4.1.3 Groundwater
The 2008 Judgment and the 2002 Settlement Agreement govern the use of groundwater in the NCMA and establish that groundwater will continue to be allotted and independently managed by the NCMA agencies, NCMA overlying owners, and SLOFCWCD (collectively known as the Northern Parties). Each of the NCMA

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agencies has the capability to extract groundwater from municipal water supply wells located in the central and northern portions of the NCMA (Figure 24, on page 62). Groundwater also satisfies agricultural irrigation and rural domestic use throughout the NCMA.

The calculated, consensus safe yield value of 9,500 AFY for the NCMA portion of the SMRVGB was formalized in the 2002 Settlement Agreement through affirmation of the 2002 Groundwater Management Agreement among the NCMA agencies. The basis of the safe yield was established in 1982 by a Technical Advisory Committee (TAC), consisting of representatives from Arroyo Grande, Grover Beach, Pismo Beach, OCSD, Avila Beach Community Water District, Port San Luis Harbor District, the Farm Bureau, and the County to deal with a safe yield allocation strategy and agreement not to exceed the safe yield of what was then called the Arroyo Grande Groundwater Basin. The basis for the committee’s analysis was DWR (1979). The TAC concluded that the safe yield was 9,500 AFY. These findings and the allocation of the safe yield were incorporated into a groundwater management plan (1983 Gentlemen’s Agreement and 2002 Groundwater Management Agreement) and further formalized in the 2002 Settlement Agreement and the 2005 Stipulation.

The 9,500 AFY safe yield provides allotments for agricultural irrigation of 5,300 AFY, subsurface outflow to the ocean of 200 AFY, and urban use entitlement of 4,000 AFY. The original volume of the entitlement for urban use was subdivided among the agencies as follows:
Arroyo Grande: 1,202 AFY
Grover Beach: 1,198 AFY
Pismo Beach: 700 AFY
OCSD: 900 AFY

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The safe yield allotment for agricultural irrigation is significantly higher than the actual historical agricultural irrigation demand, and the calculated amount for subsurface outflow is unreasonably low. Todd (2007) recognized that maintaining sufficient subsurface outflow to the coast and preservation of a westward groundwater gradient is essential to preventing seawater intrusion. A regional outflow of 3,000 AFY was estimated as a reasonable approximation (Todd, 2007), although the minimum subsurface outflow necessary to prevent seawater intrusion is unknown. The Phase 1C model (see Section 1.7.3) may be utilized in the future to further evaluate regional subsurface outflow to the ocean.

The 2002 Groundwater Management Agreement provides that groundwater entitlements of each of the urban agencies can be increased when land within the corporate boundaries is converted from agricultural use to urban use, which is referred to as an agricultural conversion credit. Agricultural conversion credits equal to 121 AFY and 209 AFY were developed in 2011 for Arroyo Grande and Grover Beach, respectively, resulting in increased entitlements of 1,323 AF and 1,407 AF, respectively. These agricultural credits were unchanged during 2024.

Total groundwater production in the NCMA, including agricultural irrigation and rural uses, is shown in Table 7 (descriptions of agricultural irrigation applied water and rural use estimation are provided in Sections

4.2.1 and 4.2.2, both below, respectively). The total estimated groundwater pumpage in 2024 from the NCMA portion of the SMRVGB was 2,949 AF.

Table 7. NCMA Groundwater Entitlement and Production from Santa Maria River Valley Groundwater Basin, 2024
Total Entitlement/Use
Groundwater Entitlement + Ag
Conversion Credit
(AF)
2024 Groundwater
Use from SMRVGB
(AF)
Total Urban Groundwater Entitlement /Use 4,000 + 330 = 4,330 522 Total NCMA Groundwater Entitlement /Use 9,500 2,949
Notes
AF= acre-feet Ag = agriculture NCMA = Northern Cities Management Area SMRVGB = Santa Maria River Valley Groundwater Basin

4.1.4 Developed Water
The 2005 Stipulation states that “developed water” is “groundwater derived from human intervention” and states that this includes infiltration from the following sources: “Lopez Lake water, return flow, and recharge resulting from stormwater percolation ponds.” Return flow results from deep percolation of water used in irrigation that is more than the requirement of the plant. Return flows have not been estimated recently but would be considered part of the groundwater basin inflow.

In 2008, Arroyo Grande, Grover Beach, and Pismo Beach prepared stormwater management plans. To control stormwater runoff and to increase groundwater recharge, each city now requires that new development construct onsite retention or detention ponds. As these new ponds or basins are constructed, the increase in groundwater recharge could result in the recognition of substantial augmentation of basin yield and provision of recharge credits to one or more of the NCMA agencies (Todd, 2007). Thus, a re-evaluation of estimated

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stormwater recharge is warranted as new recharge facilities are installed and as additional information on flow rates, pond size, infiltration rates, and tributary watershed area becomes available.

4.1.5 Other Supplies
Arroyo Grande owns three water wells that are located outside the SMRVGB and pump groundwater from the Pismo Formation. Two of the wells are pumped by the City and used for municipal consumption; the third well is likely to be used in the future. There is no established entitlement that limits the volume of groundwater that Arroyo Grande can pump from these wells, but for planning purposes, the City assumes that they can pump up to 160 AFY for municipal use. The volume that Arroyo Grande pumps from these wells varies from year to year and is included in summary totals for urban water use, but the volume is not included in the summary totals for SMRVGB production.

4.1.6 Total Water Supply Availability
The baseline, or full entitlement, water supply available to the NCMA agencies is summarized in Table 8. The baseline water supplies include 100 percent Lopez Lake entitlement, SMRVGB groundwater entitlements, agricultural credits, and 100 percent delivery of SWP allocations. This baseline water supply does not include Lopez Lake Surplus or Stored water, SWP carryover, or Stored SWP water, because these supplies vary from year to year and are not always available. The category “Other Supplies” includes groundwater pumped from outside the NCMA boundaries (outside the SMRVGB). The baseline supply for the NCMA agencies totals 10,765 AFY.

Table 8. Baseline (Full Entitlement) Available Urban Water Supplies (AFY) Agency Lopez
Lake
SWP Allocation
(at 100%)
Groundwater
Entitlement Ag Credit Other
Supplies Total
City of Arroyo
Grande 2,290 0 1,202 121 160 3,773
City of Grover Beach 800 0 1,198 209 0 2,207
City of Pismo Beach 892 1,240 700 0 0 2,832
OCSD 303 750 900 0 0 1,953
Total 4,285 1,990 4,000 330 160 10,765
Notes
AFY= acre-feet per year Ag = agriculture OCSD = Oceano Community Services District SWP = California State Water Project Table 9, summarizes the available water supply to the NCMA agencies in 2024, including Lopez Lake Entitlement, Surplus, and Stored water, the 2024 SWP Table A delivery schedule, available SWP carryover water, and available Stored SWP water. The total available water supply is a compilation of all components of each agency’s portfolio. As of 2024, reporting SWP carryover availability on an individual basis was discontinued, and that supply is now reported as a single amount of carryover water available to all the District’s subcontractors. As of January 1, 2024, 12,500 AF of SWP carryover water was available for all of the District’s subcontractors.

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Table 9. Available Urban Water Supply, 2024 (AF)
Agency Lopez Lake
Entitlement
Lopez
Lake
Surplus1
Lopez
Lake
Stored2
2024 Available
SWP Contract
Supply3
SWP
Carryover4
Stored
SWP5
Ground-
water
Entitlement
Ag
Credit
Other
Supplies Total (2024)
Arroyo
Grande 2,290 0 0 - - - 1,202 121 160 3,773
Grover
Beach 800 328 0 - - - 1,198 209 0 2,535
Pismo
Beach 892 366 0 1,240 Varies 0 700 0 0 3,198
OCSD 303 124 0 750 Varies 0 900 0 0 2,077
Total 4,285 818 0 1,990 Varies 0 4,000 330 160 11,583
Notes
All units in acre-feet (AF).
1 Lopez Lake Surplus Water is calculated based on unused downstream releases at the end of the water year (April 1 – March 31). The agencies declared their surplus water request in June 2024. The amounts listed in Table 9 were valid through December 2024 (personal communication with Desiree Bravo, SLOFCWCD, on February 14, 2025). 2 Lopez Lake Stored Project Water is derived from unused entitlement water at the end of the water year (April 1, 2024). By March 31, 2024, the agencies accumulated a total of 2,532.6 AF; however, due to Lopez Lake spilling, all stored water was lost (personal communication with Desiree Bravo, SLOFCWCD, on February 14, 2025). 3 District can supply 100% of requested delivery to meet requests that exceed the 2024 DWR Table A allocation of 40%. Full contract water of 1,240 AF and 750 AF was available for Pismo Beach and OCSD, respectively, due to surplus water from 2023. Due to the 2023 surplus, drought buffer was not a factor in water available to deliver to Pismo Beach and Oceano (personal communication with Wes Thomson, SLOFCWCD, on February 14, 2025). 4 SWP Carryover water in January 2024 for all subcontractors in the District was 12,500 AF (personal communication with Wes Thomson, SLOFCWCD, on February 14, 2025). As of 2024, all SWP carryover water is combined for the District’s use as a whole. Any agency can use SWP carryover water out of the 12,500 AF pool. 5 There was no stored SWP in 2024 for Pismo Beach or OCSD (personal communication with Desiree Bravo, SLOFCWCD, on February 14, 2025).

AF = acre-feet OCSD = Oceano Community Services District SWP = California State Water Project

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4.2 Water Use
Water use refers to the total amount of water used to satisfy the needs of all water user groups. In the NCMA, water use predominantly serves urban production and agricultural applied water; a relatively small component of rural domestic use, including small community water systems; and domestic, recreational, and agriculture- related businesses.

4.2.1 Agricultural Water Supply Requirements
For the 2024 Annual Report, the applied irrigation demand estimations were updated using the 2015 Integrated Water Flow Model (IWFM) Demand Calculator (IDC). The IDC is a stand-alone program that simulates land surface and root zone flow processes, and, importantly for this report, the agricultural water supply requirements for each crop type. IDC applies user-specified soil, weather, and land-use data to estimate and track the soil moisture balances. More specifically, available water within the root zone is tracked for each of the crops to simulate when irrigation events take place based on crop requirements and cultural irrigation practices. The data used in the IDC program for NCMA along with their respective sources are described below:
Land-use Information. The San Luis Obispo County Agricultural Commissioner’s Office compiles an annual estimate of irrigated acres in the County. A view displaying the irrigated agricultural lands within NCMA for 2024 is shown in Figure 25 on page 67. The 2024 survey indicates a total of 1,466 acres of irrigated agriculture in the NCMA consisting predominantly of rotational crops. Table 10, lists the crop types and acreages found in the NCMA that were used in the IDC program. Climate Data. The 2024 weather data from the SLOFCWCD rain gauge in Oceano and the CIMIS Nipomo Station were used for precipitation and data related to reference ET values, respectively. The data needed to calculate reference ET values include solar radiation, humidity, air temperature, and wind speed. Both weather stations are shown in Figure 6, on page 21.
ET Values by Crop Category. The DWR Consumptive Use Program (CUP) was used to estimate potential ET values based on specific annual climate data and crop type. The CUP used monthly climate data from the closest CIMIS station (Nipomo station) and applied crop coefficients to calculate ET values for the irrigated crop categories.

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Assumptions used in the analysis include the following:
As the NCMA is located near the coast, agricultural practices are influenced significantly by the marine layer, a mass of air that may be of lower temperature and have higher humidity than air over inland areas.

As seen in Figure 6, on page 21, the Nipomo CIMIS station used for climatological data in both the CUP and IDC is located farther inland than the easternmost boundary of NCMA and the recorded weather data does not fully account for the cooling and moisture effects of the marine layer. Use of an unadjusted calculated ET value results in a higher ET value than is taking place in the NCMA.

Studies 26 have identified that ET values within the influence of the marine layer can be as much as 20 to 25 percent lower than ET values for the same crop located just outside of the marine layer influence. The distance the marine layer extends inland can vary from less than one-half mile to as much as 4 to 5 miles, depending on land topography. Low-lying areas have a higher frequency of marine layer coverage and for longer periods throughout the day.
The NCMA is considered a low-lying area with boundaries extending between 2 and 5 miles inland.

Recognizing that not all the crops would be affected by the marine layer but accounting for the cooling influence over some of the area, monthly ET values calculated based on the CIMIS Nipomo Station data were adjusted lower by 12 percent27 and are shown in Table 10. Soil Data. The Natural Resources Conservation Service Soil Survey Geographic Database was used to collect soil parameters in the NCMA for use in the IDC. The soil properties used include saturated hydraulic conductivity, porosity, and runoff curve numbers. The field capacity and wilting points were developed on the basis of the described soil textures (i.e., sand, loam, sandy clay) and industry standards. The IDC relies on soil properties for estimating water storage, deep percolation, and runoff; all of which lead to a refined estimation of applied water.

Table 10. NCMA Crop Acreages and Calculated Evapotranspiration, 2024 Crop Type Acreage 2024 Potential ET1
(AF/Acre)
Rotational Crops 1,249 2.1 2
Strawberries 175 1.9
Avocados 42 2.1
Notes
1 See ET Values by Crop Category, in text section above. 2 Rotational crop ET is based on a rotation of two to three crops.

AF = acre-feet ET = evapotranspiration NCMA = Northern Cities Management Area 26 Irrigation Training and Research Center http://www.itrc.org/etdata/etmain.htm > (Cal Poly, 2019) provides typical-year (1997 Hydrology) ET values using various irrigation methods for Zone 3, the coastal outside marine layer; and Zone 1, the marine layer. The computed percentage reduction in ET to Zone 3 values range from 11 percent for rotational crops (small vegetables) to 19 percent for strawberries.
27 A single ET reduction value is used based on changing location and rotation of crop types relative to influence of marine layer.

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Model Development and Computations
The IDC is written in FORTRAN 2003 using an object-oriented programming approach. The program consists of three main components: (1) input data files, (2) output data files, and (3) the numerical engine that reads data from input files, computes applied water demands, routes water through the root zone, and exports the results to the output files. The flow terms used in the root zone routing are defined in Table 11, and shown in the graphic below the table. Drainage from ponded areas (Dr) was not applicable because there are no ponded crops in the NCMA; data related to generic soil moisture (G) were not available.

Table 11. Flow Terms Used in Root Zone Routing for IDC Model Abbreviation Term Notes
P Precipitation User Specified
ET Evapotranspiration IDC Output
G Generic source of moisture (i.e., fog, dew) Data Not Available Aw Applied water IDC Output
Dr Outflow resulting from drainage of ponded
areas (e.g., rice, refuges) Not Applicable
RP Direct runoff IDC Output
Rf Return flow User Specified (fraction of applied water) U Re-used portion of return flow User Specified (fraction of return flow) D Deep percolation IDC Output
Note
Integrated Water Flow Model (IWFM) Demand Calculator (IDC) (DWR, 2016) Source: DWR (2016).

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All extracted geospatial information was applied to a computational grid within the IDC framework to simulate the root zone moisture for 2024 in NCMA agricultural areas. The IDC provides the total water supply requirement for each crop category met through rainfall and applied irrigation water in agricultural areas based on user-defined parameters for crop evaporation and transpiration requirements, climate conditions, soil properties, and agricultural management practices. The sources for data related to crop demands (i.e., potential ET), climate conditions, and soil properties are discussed above. The computations for actual crop ET (versus potential ET), applied water, and deep percolation are described below.

The potential ET is the amount of water a given crop will consume through evaporation and/or transpiration under ideal conditions (i.e., fully irrigated 100 percent of the time). Fully irrigated conditions mean that the water required to meet all crop demands is available. Water is available to the crops when the soil moisture content within the root zone is between the field capacity and the wilting point. When the soil moisture is above the field capacity, some water will go to runoff and/or deep percolation; when the soil moisture is below the wilting point, it is contained in the smallest pore spaces within the root zone and considered unavailable to the crops.

The difference between the field capacity and the wilting point is the Total Available Water. In IDC, when the soil moisture is above one-half of the Total Available Water, the crop ET will be equal to the potential ET.

However, if the soil moisture is below one-half of the Total Available Water, the plants will experience water stress and ET decreases linearly until it reaches zero at the wilting point. This method of simulating water stress is similar to the method described in Allen et al. (1998) to compute non-standard crop ET under water stress conditions.

The IDC monitors the moisture content within the root zone and applies water by triggering an irrigation event when the calculated soil moisture is below a user-specified minimum allowable soil moisture requirement. For this application of the IDC, the minimum soil moisture requirement was set to trigger an irrigation event when the soil moisture fell below one-half the Total Available Water to limit water stress in the crops. During an irrigation event, the soil moisture content in the root zone reaches field capacity. If precipitation occurs, soil moisture may increase above field capacity, generating deep percolation and potentially runoff, both depending on the quantity and temporal distribution of rainfall.

Deep percolation is the vertical movement of water through the soil column flowing out of the root zone resulting in the potential for groundwater recharge. The IDC applies the van Genuchten-Mualem equation (Mualem, 1976; van Genuchten, 1985) to compute deep percolation using the user-defined saturated hydraulic conductivity and pore size distribution.

Results
The total agricultural water supply requirement for 2024 was estimated to be 2,307 AF, and the effective precipitation (i.e., rainwater used by the crop) was 671 AF. Precipitation totaled 15.43 inches during 2024, with the most precipitation occurring in February (3.83 inches) and March (3.59 inches), which reduced the need for early-season irrigation. This was significantly lower than 2023, which received 23.75 inches of precipitation. The reduction in rainfall led to less moisture stored in the soil, decreasing its ability to satisfy crop water demand and increasing reliance on irrigation. Figure 26, on page 71, illustrates the estimated crop water requirement in the NCMA as calculated by the IDC and displays the three identified crop types and their estimated monthly applied water. The rotational crops have the highest water supply requirements because they cover the greatest area (see Figure 25, on page 67) and have the greatest annual ET (Table 12).

The area-weighted average applied water for NCMA in 2024 was 1.58 AF per acre, aligning with previous estimates and expected trends based on ET demand and crop water requirements. The Irrigation Efficiency for 2024 was estimated as the sum of the ET of applied water over the sum of applied water. The overall irrigation efficiency for the area is 86 percent.

FIGURE 26.
2024 ESTIMATED AGRICULTURAL WATER DEMAND AND MONTHLY PRECIPITATION AT THE SLO NO. 795 GAUGE Northern Cities Management Area
San Luis Obispo County, California
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Table 12. IDC Model Results of Monthly Applied Water, 2024 Monthly Applied Water (AF)
Annual Total (AF)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rotational Crops -- -- -- 381 420 426 444 375 -- -- -- -- 2,046 Strawberries -- -- -- 10 30 56 44 44 29 -- -- -- 212.5
Avocados -- -- -- -- 5 10 10 10 7 6 -- -- 47.8
Total 0 0 0 391 456 491 499 428 36 6 0 0 2,307
Monthly Precipitation (inches) Annual Total
(inches) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Precipitation 1.92 3.83 3.59 2.21 0.03 0.01 0 0.01 0.02 0.04 2.80 0.97 15.43 Monthly Unit Water Demand (AF/Acre) Annual Total
(AF/acre) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rotational Crops --- --- --- 0.31 0.34 0.34 0.36 0.30 0.30 --- --- --- 1.64 Strawberries --- --- --- 0.06 0.17 0.32 0.25 0.25 0.16 --- --- --- 1.21 Avocados --- --- --- --- 0.12 0.23 0.24 0.23 0.17 0.14 --- --- 1.13 Area Weighted Average 0.00 0.00 0.00 0.27 0.31 0.33 0.34 0.29 0.02 0.00 0.00 0.00 1.58 Notes
— = not applicable AF = acre-feet AF/acre = acre-feet per acre

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4.2.2 Rural Use
In the NCMA, rural water use refers to groundwater pumping not designated as urban use or agricultural irrigation applied water and includes small community water systems, individual domestic water systems, recreational uses, and agriculture-related business systems. Small community water systems using groundwater in the NCMA were identified initially through a review of a list of water purveyors compiled in the 2007 County IRWMP. These include the Halcyon Water System, Ken Mar Gardens, and Pacific Dunes RV Resort. The Halcyon Water System serves 35 homes in the community of Halcyon, and Ken Mar Gardens provides water supply to 48 mobile homes on South Halcyon Road. The Pacific Dunes RV Resort, with 215 RV sites, provides water supply to a largely transitory population and a nearby riding stable. In addition, an inspection of aerial photographs of rural areas within NCMA has identified about 25 homes and businesses that are served by private wells. Two mobile home communities, Grande Mobile and Halcyon Estates, are served by OCSD through the distribution system of Arroyo Grande. Therefore, the production summary of OCSD includes these two communities. Based on prior reports, it is assumed that the number of private wells is negligible within the service areas of the NCMA agencies.

The Pismo Beach Golf Course uses an onsite water well for turf irrigation. The pumped water is not metered, and the golf course operators do not know the total water use. An estimate of water demand for the golf course is based on the irrigated acreage, sandy soils, near-ocean climate, and water duty factors from the U.S. Golf Association, Alliance for Water Efficiency, U.S. Golf Courses Organization of America, and several other sources. The estimated rural water demand is provided in Table 13.

Table 13. Estimated Rural Water Production, 2024
Groundwater User No. of Units
Estimated Water
Production,
AFY per Unit
Estimated Annual
Water Production
(AF)
Halcyon Water System1 35 0.4 14
Ken Mar Gardens2 48 — 4.5
Pacific Dunes RV Resort3 215 0.03 6.5
Pismo Beach Golf Course4 — — 45
Rural Users1 25 0.4 10
Current Estimated Rural Production 80
Notes
1 Rural residential water use is assumed to include minor outdoor irrigation and is estimated at 0.4 AFY per unit. 2 Demand based on metered water usage.
3 Water use/unit assumes 50 percent annual occupancy and 0.06 AFY per occupied site. 4 Estimated golf course demand, based on estimated water duty factor, annual ET, and irrigated acreage. — = not applicable AF=acre feet
AFY = acre-feet per year ET = evapotranspiration

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4.2.3 Urban Production for Potable Use
Urban water production for potable use is presented in Table 14, for each of the NCMA agencies from 2005 through 2024. These values reflect Lopez Lake deliveries, SWP deliveries, groundwater production data, and system losses, and represent all water used within the service areas of the four NCMA agencies. In the last 18 years, urban water production has ranged from 5,240 AF (2023) to 8,982 AF (2007). There has been an overall decline in urban production since 2007. The long-term declining trend in production was likely initially attributed to the relatively slow economy from 2009 through 2012, then subsequently to conservation activities implemented by the NCMA agencies in response to drought conditions. Urban water production was 5,356 AF in 2024, the second lowest level in at least the last 20 years.

Table 14. Historical Urban Water Production for Potable Use (Groundwater and Surface Water) Year Arroyo
Grande
Grover
Beach
Pismo
Beach OCSD Total
Urban
Percentage of 2013
Production1
2005 3,460 2,082 2,142 931 8,615 —
2006 3,425 2,025 2,121 882 8,453 —
2007 3,690 2,087 2,261 944 8,982 —
2008 3,579 2,051 2,208 933 8,771 —
2009 3,315 1,941 2,039 885 8,180 —
2010 2,956 1,787 1,944 855 7,542 —
2011 2,922 1,787 1,912 852 7,473 —
2012 3,022 1,757 2,029 838 7,646 —
2013 3,111 1,792 2,148 888 7,939 —
2014 2,752 1,347 1,949 807 6,856 —
2015 2,239 1,265 1,736 703 5,943 75%
2016 1,948 1,210 1,646 672 5,476 69%
2017 2,194 1,248 1,700 718 5,860 74%
2018 2,212 1,221 1,720 725 5,878 74%
2019 2,139 1,193 1,648 680 5,660 71%
2020 2,317 1,289 1,777 743 6,126 77%
2021 2,307 1,277 1,771 718 6,073 76%
2022 1,990 1,205 1,632 644 5,471 69%
2023 1,936 1,166 1,509 629 5,240 66%
2024 2,024 1,227 1,494 611 5,356 67%
Notes
1 On April 1, 2015, California Governor Jerry Brown issued an executive order (B29-2015) mandating statewide reductions in water use. The order directs the State Water Resources Control Board to implement mandatory water reductions in cities and towns across California to reduce water usage by 25 percent, compared to the amount used in 2013, through February 2016.

All units in acre-feet (AF)
— = not applicable AF = acre-feet OCSD = Oceano Community Services District

4.2.4 2024 Groundwater Pumpage
Total SMRVGB groundwater production in the NCMA, including urban production, applied agricultural water requirements, and rural pumping, is shown in Table 15. The total estimated SMRVGB groundwater pumpage in the NCMA in 2024 was 2,949 AF, which represents an increase from 2023 (2,697 AF).

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Table 15. NCMA Groundwater Pumpage from Santa Maria River Valley Groundwater Basin, 2024 (AF) Agency
Groundwater
Entitlement + Ag
Conversion Credit
(AF)
2024 Groundwater
Use from SMRVGB
(AF)
Percent Pumped of
Groundwater
Entitlement
Arroyo Grande 1,202 + 121 = 1,323 59 4%
Grover Beach 1,198 + 209 = 1,407 436 31%
Pismo Beach 700 15 2%
OCSD 900 12 1%
Total Urban Groundwater
Entitlement /Use 4,000 + 330 = 4,330 522 12%
Agricultural Irrigation Applied
Water 5,300 - 330 = 4,970 2,307 46%
Non-potable Applied Irrigation
Water (Arroyo Grande) — 40 —
Rural Water Users — 80 —
Estimated Subsurface Outflow
to Ocean (2002 Groundwater
Management Agreement)
200 — —
Total NCMA Groundwater
Entitlement /Use 9,500 2,949 31%
Notes
— = not applicable AF = acre-feet Ag = agriculture NCMA = Northern Cities Management Area OCSD = Oceano Community Services District SWRVGB = Santa Maria River Valley Groundwater Basin

The total estimated groundwater pumpage of 2,949 AF in 2024 represents about 31 percent of the calculated safe yield of 9,500 AFY for the NCMA portion of the SMRVGB.

A graphical depiction of water uses by supply source for each NCMA agency since 2000 is presented as Figure 27, on page 76. The graphs depict changes in water supply availability and use over time. The increased dependence on Lopez Lake in 2017, 2018, 2019, and 2020 is illustrated in this graphic. With reduced access to Lopez Lake water in 2021 and 2022, OCSD and the City of Pismo Beach utilized a greater percentage of SWP water during that time. In 2024, the availability of Lopez Lake spill water during February, March, April, May, and June resulted in reduced use of SWP water during that time. Although all four agencies pumped groundwater as part of their supply portfolios in 2024, groundwater pumped from the SMRVGB constituted a minor part of the overall water supply, an amount of 562 AF28 or 10 percent of overall NCMA use 29.

28 This total includes the 522 AF pumped by NCMA agencies and the 40 AF of non-potable irrigation production in Arroyo Grande.
29 Total water use includes potable and non-potable groundwater extraction from all four NCMA agencies, surface water from Lopez Lake, and SWP water. 2024 total water use equals 5,356 AF.

FIGURE 27. MUNICIPAL WATER USE BY SOURCE
Northern Cities Management Area
San Luis Obispo County, California
Notes:

AFY - Acre-feet per year
SWP - California State Water Project
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As shown in Figure 28, on page 78, groundwater pumpage reached a peak in 2007 and then declined in 2008, 2009, and 2010. From 2010 through 2013, pumpage increased slightly every year, but overall groundwater use remained significantly lower than previous annual pumpage rates. Annual pumping totals have generally been decreasing since 2013. In 2024, urban potable groundwater use was 522 AF, which is 12 percent of the 4,330 AF of combined urban groundwater entitlement and agricultural conversion credit.

4.2.5 Changes in Water Production
Historical water use for urban uses, agricultural irrigation, and rural uses is shown in Table 16.

Table 16. Historical Total Water Use (Groundwater and Surface Water, AF) Year Arroyo
Grande
Grover
Beach
Pismo
Beach OCSD Total
Urban
Agricultural
Irrigation1
Rural
Water Total Use
2005 3,460 2,082 2,142 931 8,615 2,056 36 10,707
2006 3,425 2,025 2,121 882 8,453 2,056 36 10,545
2007 3,690 2,087 2,261 944 8,982 2,742 36 11,760
2008 3,579 2,051 2,208 933 8,771 2,742 36 11,549
2009 3,315 1,941 2,039 885 8,180 2,742 36 10,958
2010 2,956 1,787 1,944 855 7,542 2,056 38 9,636
2011 2,922 1,787 1,912 852 7,473 2,742 38 10,253
2012 3,022 1,757 2,029 838 7,646 2,742 41 10,429
2013 3,111 1,792 2,148 888 7,939 2,742 42 10,722
2014 2,752 1,347 1,949 807 6,855 2,955 38 9,848
2015 2,239 1,266 1,736 703 5,943 3,008 38 8,990
2016 1,948 1,210 1,646 672 5,476 2,551 81 8,108
2017 2,194 1,248 1,700 718 5,860 2,579 80 8,519
2018 2,212 1,221 1,720 725 5,878 2,713 81 8,672
2019 2,139 1,193 1,648 680 5,660 2,554 82 8,296
2020 2,317 1,289 1,777 743 6,126 2,369 82 8,577
2021 2,307 1,277 1,771 718 6,073 2,503 82 8,658
2022 1,990 1,205 1,632 644 5,471 2,614 80 8,165
2023 1,936 1,166 1,509 629 5,240 2,083 80 7,403
2024 2,024 1,227 1,494 611 5,356 2,347 80 7,783
Notes
1 Irrigation-applied water includes agricultural irrigation plus SMRVGB non-potable irrigation by Arroyo Grande.

AF = acre-feet OCSD = Oceano Community Services District SMRVGB = Santa Maria River Valley Groundwater Basin

FIGURE 28. TOTAL WATER USE (URBAN, RURAL, AGRICULTURAL) BY SOURCE Northern Cities Management Area
San Luis Obispo County, California
P:\672-Northern Cities Management Area\NCMA Muni Pumping Notes:

AFY - Acre-feet per year
SWP - California State Water Project
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In general, urban water production has ranged from 8,982 AF in 2007 (Table 16) to 5,240 AF in 2023. Total water use since 2007 has been on a general downward trend; this overall decline in water use can be attributed to conservation activities implemented by the NCMA agencies in response to drought. 2024 urban water use is the second lowest on record. This may be attributed to conservation mechanisms already in place coupled with reduced urban landscaping water demand due to above-average precipitation during winter 2023/2024.

In the agricultural irrigation category, agricultural acreage has remained fairly constant. Thus, annual applied water for agricultural irrigation varies mostly with climatic conditions. Acknowledging the variability caused by climatic conditions, agricultural irrigation-applied water is not expected to change significantly, given the relative stability of applied irrigation acreage and cropping patterns in the NCMA south of Arroyo Grande Creek.

Similarly, no significant changes in rural domestic pumping are assumed to have occurred.

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SECTION 5: Comparison of Water Supply and Water Production The Baseline Available Urban Water Supplies for each of the NCMA agencies is 10,765 AFY, assuming 100 percent delivery of SWP allocation and assuming no Lopez Lake Surplus or Stored water, or SWP carryover or Stored SWP water (Table 8). In 2024, despite the 40 percent SWP Table A allocation set by the DWR, 100 percent of SWP allocation was available to agencies in the SLOFCWCD due to excess water from 2023. In addition, Lopez Lake Surplus water and SWP carryover water were available to the agencies. The total available urban water supply in 2024 was 11,583 AF (Table 9), not including the 12,500 AF of SWP carryover water available to split amongst all agencies in the SLOFCWCD.

As described in the 2002 Groundwater Management Agreement and affirmed in the 2002 Settlement Agreement, the calculated safe yield from the NCMA portion of the SMRVGB is 9,500 AFY (Table 8, and Table 15). Because all agricultural irrigation water use is supplied by groundwater, the total available agricultural irrigation supply is a portion of the estimated safe yield; this portion was allocated as 5,300 AFY for agricultural and rural use. The agricultural conversion of 330 AFY reduces this allocation to 4,970 AFY. Of the estimated safe yield of 9,500 AFY, other than what is allocated for agricultural irrigation and rural use, the remaining 4,330 AFY is allocated for urban water use (4,330 AFY, including 4,000 AFY groundwater allocation plus 330 AFY in agricultural conversion credit) and an estimated 200 AFY for subsurface outflow to the ocean.

In 2024, the total estimated NCMA water production was 7,783 AF (Table 17). The 2024 water production of each city and agency is shown by source in Table 17. Note that the production volumes described here are gross production (if pumped groundwater) and gross deliveries (if surface water deliveries) and equal net consumptive demand plus losses and return water.

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Table 17. Water Production by Source, 2024 (AF)
Agency Lopez Lake
State
Water
Project
SMRVGB
Groundwater
Other
Supplies1 Total
Urban Area
Arroyo Grande 1,965 0 59 0 2,024
Grover Beach 791 0 436 0 1,227
Pismo Beach 1,099 380 15 0 1,494
OCSD 318 281 12 0 611
Urban Water Use
Total 4,173 661 522 0 5,356
Non-Urban Area
Agricultural Irrigation
Applied Water 0 0 2,307 0 2,307
Rural Water Users 0 0 80 0 80
Non-potable Applied
Irrigation Water
(Arroyo Grande)
0 0 40 0 40
Total 4,173 661 2,949 0 7,783
Notes
1 The category “Other Supplies” includes groundwater pumped from outside the NCMA boundaries.

AF = acre-feet NCMA = Northern Cities Management Area
OCSD = Oceano Community Services District SMRVGB = Santa Maria River Valley Groundwater Basin

As shown in Table 17, water for urban use in 2024 was supplied to the NCMA from 4,173 AF of Lopez Lake water, 661 AF of SWP water, and 522 AF of groundwater. Arroyo Grande produced 0 AF from its Pismo Formation wells in 2024.

Based on the calculated yield of the NCMA portion of the SMRVGB, the baseline, or full allocation, of total available supply for all uses is 15,735 AFY, which is the sum of 10,765 AFY for urban use plus the allocation for agricultural irrigation and rural area of 4,970 AFY. In 2024, factoring in the SWP delivery schedule, the total available supply for all users was 11,583 AF (Table 9) compared with the actual 2024 NCMA water use of 7,783 AF (Table 17). It must be noted, however, that this comparative review of the available 2024 supply versus production must be viewed with caution because of the potential threats to the groundwater supply (see Section 6.1). As described earlier, the NCMA agencies pumped only 12 percent of their “available” groundwater entitlement. Based on available data, the NCMA agencies could not have used their entire groundwater entitlement in 2024 without lowering groundwater elevations and offsetting the welcome gains in groundwater in storage (see Section 3.2).

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SECTION 6: Threats to Water Supply
Because the NCMA agencies depend on both local and imported water supplies, changes in either state-wide or local conditions can threaten the NCMA water supply. Water supply imported from other areas of the state may be threatened by state-wide drought, effects of climate change in the SWP source area, management and environmental protection issues in the Delta that affect the amount and reliability of SWP deliveries, and risk of seismic damage to the SWP delivery system. Local threats to the NCMA water supply similarly include extended drought and climate change that may affect the yield from Lopez Lake and reduced recharge to the NCMA. In addition, the NCMA is not hydrogeologically isolated from the NMMA and the rest of the SMRVGB, and water supply threats in the NMMA are a potential threat to the water supply sustainability of the NCMA.

There is a potential impact from seawater intrusion if the groundwater system, including the entire SMRVGB, is not adequately monitored and managed. In particular, management of the SMRVGB may need to account for sea level rise and the relative change in groundwater gradient along the shoreline.

6.1 Threats to Local Groundwater Supply

6.1.1 Declining Water Levels
Before 2023, water levels in the NCMA portion of the SMRVGB exhibited an overall declining trend for many years. Important factors for maintaining water levels are managing inflow and outflow to the aquifer. Inflow: An important inflow component to the NCMA area is subsurface inflow into the aquifers that supply water wells serving the NCMA. Historically, subsurface inflow to the NCMA from the Nipomo Mesa along the southeast boundary of the NCMA has been a primary component of groundwater recharge. This inflow is reduced from historical levels, as first recognized in 2008–2009, to “something approaching no subsurface flow” because of lower groundwater levels in the NMMA (NMMA 2nd Annual Report CY 2009, page 43) (NMMA, 2010). This condition continues, as described in all subsequent NMMA annual reports. Outflow: A major outflow component is groundwater pumpage. Total SMRVGB groundwater pumping in the NCMA (urban, agricultural, and rural domestic) was 2,949 AF in 2024 (see Table 7), which is 31 percent of the court-accepted 9,500 AF safe yield of the NCMA portion of the SMRVGB. Even during the above average precipitation years in 2023 and 2024, the NCMA agencies could not have used their entire groundwater entitlement without lowering groundwater elevations and offsetting the welcome gains in groundwater in storage (see Section 3.2).

Before 2023, recent drought conditions had resulted in a generally steady decline in groundwater in storage in the NCMA portion of the SMRVGB. Although above-average precipitation received in 2023 and 2024 resulting in increased water levels and a positive change in groundwater in storage, the estimated 530 AF increase in groundwater in storage in 2024 is only approximately equivalent to 15 percent of a single year’s worth of total NCMA groundwater pumping (based on pumping totals since 201030). Although there was a positive change in groundwater in storage, minimal groundwater recharge could return the NCMA to a state of declining groundwater levels, which could be exacerbated if the NCMA agencies are required to increase groundwater withdrawals because of a reduction or total loss in local surface water supplies or SWP deliveries. 30 Average groundwater extraction in NCMA from 2010 through the present is 3,587 AF.

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6.1.2 Seawater Intrusion
The NCMA is underlain by an accumulation of alluvial materials that slope gently offshore and extend for many miles under the ocean (DWR, 1970, 1975). Coarser materials within the alluvial materials comprise aquifer zones that receive freshwater recharge in areas above sea level. If sufficient outflow from the aquifer occurs, the dynamic interface between seawater and fresh water will be prevented from moving onshore. Sufficient differential pressure to maintain a net outflow is indicated by onshore groundwater elevations that are above mean sea level and establish a seaward gradient to maintain that outflow.

The 2008 NCMA Annual Report documented that a portion of the aquifer underlying the NCMA exhibited water surface elevations below 0.0 feet (NAVD 88) (NCMA, 2008). Hydrographs for NCMA sentry wells and the Deep Well Index (Figures 11 through 15, on pages 3232 through 37) show that coastal groundwater elevations were at relatively low levels for as long as 2 years during that time. Such sustained low levels had not occurred previously in the historical record and reflected the impact of drought on groundwater levels. The low coastal groundwater levels indicated a potential for seawater intrusion.

Elevated concentrations of TDS, chloride, and sodium were observed in wells 30N03 and 30N02 beginning in May 2009, indicating incipient seawater intrusion (Figure 29, on page 85, and Figure 30, on page 86). OCSD MW-Blue also showed elevated concentrations of TDS and chlorides, but a concurrent decline in sodium (Figure 30, on page 86). Concentrations of TDS, chloride, and sodium recovered to historical levels in wells 30N03 and 30N02 (one of the sentry wells comprising the Deep Well Index) by April 2010. Comparing well 30N02 to the other Deep Well Index wells, the other Deep Well Index wells showed no elevated concentrations during the same period. However, comparing well 30N02 to wells with similar screen elevations (Figure 4, on page 16), wells 36L01 (approximately 12,000 feet south of well 30N02) and the OCSD MW-Blue well, approximately 3,300 feet east-southeast of well 30N02, suggested that seawater intrusion perhaps progressed eastward as far as the OCSD MW-Blue well, but not as far south as well 36L01 (Figure 30, on page 86). While the TDS and chloride concentrations were elevated from August 2009 to July 2011 in the OCSD MW-Blue well, the sodium concentrations remained within historical levels. During the same period, TDS, chloride, and sodium concentrations remained relatively stable in well 36L01.

During 2024, there were no indications of seawater intrusion from data and samples collected from the Sentry wells.

1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 0 500
1,000
1,500
2,000
2,500
TD
S
,

m
g
/
L
0 20
40 60
80 100
120
140
160
180
200
Ch
l
o
r
i
d
e
,

m
g
/
L
0 40
80 120
160
200
240
280
So
d
i
u
m
,

m
g
/
L
Well 24B03 (Careaga Sand)
Well 30F03 (Careaga Sand) Index Wells
Well 30N02 (Paso Robles Formation)
Well 30N03 (Paso Robles Formation)
P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 29 NCMA TDS, Cl and Sodium Index Wells and 30N03 }
30N02 Chloride
>600 mg/l
in 2009
Notes:

TDS - total dissolved solids
mg/L - milligrams per liter
FIGURE 29. HISTORICAL TDS, CHLORIDE AND SODIUM, INDEX WELLS AND 30N03 Northern Cities Management Area
San Luis Obispo County, California
85 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 0 500
1,000
1,500
2,000
2,500
TD
S
,

m
g
/
L
0 20
40 60
80 100
120
140
160
180
200
Ch
l
o
r
i
d
e
,

m
g
/
L
0 40
80 120
160
200
240
280
So
d
i
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,

m
g
/
L
Well 30N02 (Paso Robles Formation)
Well 31H11 (Blue; Paso Robles Formation)
Well 36L01 (Paso Robles Formation)
P:\672-Northern Cities Management Area\_Grapher Figures\Annual Rpt Figs Fig 30 NCMA TDS, Cl and Sodium Wells 30N02 MW-Blue and 36L01_v2 Notes:

TDS - total dissolved solids
mg/L - milligrams per liter
31H11 Chloride
1,000 mg/l
in 2009
FIGURE 30. HISTORICAL TDS, CHLORIDE AND SODIUM, WELLS 30N02, MW-BLUE AND 36L01 Northern Cities Management Area
San Luis Obispo County, California
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Measures to Avoid Seawater Intrusion
In recognition of the risk of seawater intrusion, the NCMA agencies have developed and implemented a water quality monitoring program for the sentry wells and OCSD observation wells. The NCMA agencies and SLOFCWCD have worked cooperatively toward the protection of the sentry wells as long-term monitoring sites.

Several measures are employed by the NCMA agencies to reduce the potential for seawater intrusion.

Specifically, the NCMA agencies have voluntarily reduced coastal groundwater pumping; decreased overall water use via conservation; and initiated plans, studies, and institutional arrangements to secure additional surface water supplies. As a result, each of the four major municipal water users in the NCMA reduced groundwater use between 25 and 95 percent during the past several years. In 2024, potable municipal groundwater use was 522 AF, which constitutes 12 percent of the urban users’ groundwater entitlement (including agricultural conversion credits) of the safe yield (Table 7).

According to the DWR Bulletin 63-3 report (DWR, 1970) both the Paso Robles Formation aquifer and the lower confined portion of the Cienega Valley alluvial aquifer are recharged primarily from subsurface groundwater inflow from the east, where the overlying confining layers are thin to nonexistent (DWR, 1970). These recharge areas to the east include inland reaches of Arroyo Grande Valley and portions of Nipomo Mesa (DWR, 1970).

Any action that results in reduced groundwater recharge, whether it is from drought or reduction of subsurface inflow from the north and east, reduces overall recharge to the groundwater basin, lowers the gradient (or head) of the groundwater near the shoreline, and reduces subsurface outflow to the ocean, thereby increasing the potential threat of seawater intrusion. Alternatively, any action that results in increased groundwater recharge lessens the threat of seawater intrusion.

On March 18, 2024, the CCBRRWA Board of Directors received an update on the Central Coast Blue Project describing increases in costs, a loss of state grant funding, and improvements in local water supply conditions have prompted leaders to stop design and permitting activities for the project until the impacts of these recent developments can be evaluated (CCBRRWA, 2024). The project is a major initiative intended to provide protection against the threat of seawater intrusion. Central Coast Blue is a regional recycled water project that includes advanced treatment of water from the WWTPs of Pismo Beach and SSLOCSD and injection into the NCMA portion of the SMRVGB. In response to these funding challenges, the partner agencies will re-evaluate their current water supply needs and consider Project alternatives. Arroyo Grande and Grover Beach have withdrawn from the Central Coast Blue Project as originally conceived. Additionally, the program management team is exploring options that would reduce project costs and leaders are advocating to secure additional grants. As a result, project construction—initially planned to break ground in summer 2024—has been delayed (CCBRRWA, 2024). See Section 1.7 for a description of the Central Coast Blue Project.

In 2020 the Nipomo Community Services District (NCSD) asked the NCMA agencies for a letter in support of an appeal to the Santa Barbara County Board of Supervisors to remove the 3,000 AFY volume limitation in the NCSD waterline intertie license agreement. NCSD has designed and constructed a pipeline for the Nipomo Supplemental Water31 project (Supplemental Water Project) that is sized to accommodate the delivery of 6,200 AFY as provided for in the Stipulation and Judgment. It is NCSD’s contention that the 3,000 AFY limitation in the license agreement is arbitrary, serves no purpose, and is in violation of Santa Barbara County’s obligations under the Stipulation and Judgment to support, and not oppose, implementation of the 31 As described in Section VI.A of the Stipulation; “The NCSD agrees to purchase and transmit to the [Nipomo Mesa Management Area] (NMMA) a minimum of 2,500 acre-feet of Nipomo Supplemental Water each Year. However, the NMMA Technical Group may require NCSD in any given Year to purchase and transmit to the NMMA an amount in excess of 2,500 acre-feet and up to the maximum amount of Nipomo Supplemental Water which the NCSD is entitled to receive under the MOU if the Technical Group concludes that such an amount is necessary to protect or sustain Groundwater supplies in the NMMA.”

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Adjudication, including development of the Supplemental Water Project. Further, the limitation threatens the long-term sustainability of the entire Basin. Completion of the Supplemental Water Project is intended to reduce groundwater pumping, increase subsurface inflow from Nipomo Mesa to the NCMA, and help protect the groundwater resource from seawater intrusion. The NCMA agencies supplied the requested letter of support to NCSD on February 19, 2021.

6.2 Threats to State Water Project Supply
Both extended drought and long-term reduction in snowpack from climate change can affect SWP deliveries.

The storage capacity levels of the state’s two largest reservoirs, Lake Shasta and Lake Oroville, were 69 percent and 70 percent capacity, respectively, at the start of 2024. As a result of above average precipitation and snowpack during the winter of 2023/2024, Lake Shasta filled to about 97 percent and Lake Oroville filled to 100 percent by late spring 2024. Due to the continued accumulation of precipitation and snowpack throughout winter and spring of 2024, DWR reported that water supply and snowpack conditions remained around historical averages. The DWR allowed 40 percent fulfillment of Table A allocations for 2024.

Leading into 2024, rainfall totaled about 4.5 inches in December 2023 as recorded at the County-operated gauge (No. SLO 795). Although the calendar year rainfall total at the No. SLO 795 station for 2024 (15.63 inches) is considered to be an average water year, above-average precipitation occurred during the winter and early spring of 2023/2024, contributing to watersheds and groundwater recharge areas to the east of the NCMA. Rainfall received during 2024 at County monitored stations Arroyo Grande Creek (No. SLO 739) and Lopez Dam (No. SLO 737) were 17.7 and 26.7 inches, respectively.

The immediate threat of allocation reductions to Pismo Beach and OCSD, the only SWP subcontractors in the NCMA, has not significantly materialized during the past several years. The SLOFCWCD’s unsubscribed Table A entitlement provides a buffer, in addition to the agency’s drought buffer, so that contracted volumes to SWP subcontractors, such as the OCSD and Pismo Beach, may still be provided in full. However, the SWP supply has the potential to be affected by drought as well as environmental issues. Twenty-year projected climate change scenarios documented in DWR (2024) modeled the estimated average annual delivery of Table A water to be 13 percent to 22 percent lower than under existing conditions.

6.3 Threats to Lopez Lake Water Supply
Despite the filling and subsequent spilling of Lopez Lake reservoir in 2023 and 2024, pre-2023 extended drought conditions contributed to recent record-low water levels in Lopez Lake. As discussed in Section 4.1.1, , the Zone 3 agencies developed and implemented the LRRP in response to reduced water in storage in the lake in recent years. The LRRP is intended to reduce municipal diversions and downstream releases as water levels drop to preserve water within the reservoir for an extended drought. Water from Lopez Lake may be significantly reduced or unavailable to the Zone 3 agencies in the event of a prolonged future drought. Without access to water from Lopez Lake, the NCMA agencies and local agriculture stakeholders may be forced to rely more heavily on their groundwater supplies and increase pumping during extended drought conditions, which could result in lowering water levels in the aquifer and an increased threat from seawater intrusion. Moreover, a reduction in downstream releases from the reservoir, as mandated by the LRRP, likely will lead to reduced recharge to the NCMA portion of the SMRVGB and further contribute to declining groundwater levels.

6.3.1 Environmental Litigation (San Luis Obispo Coastkeeper vs. County of San Luis Obispo)
In August 2024, a coalition of four environmental groups (San Luis Obispo Coastkeeper, Los Padres ForestWatch, California Coastkeeper Alliance, and Ecological Rights Foundation) filed a lawsuit alleging that

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the County, which operates the Lopez Project as SLOFCWCD Zone 3, is in violation of the Endangered Species Act, and requested an increase of releases from the Lopez Dam to support steelhead populations, and to provide fish passage past the dam. In December 2024, U.S. District Judge Sherilyn Peace Garnett ruled in favor of the plaintiffs and ordered a preliminary injunction that requires the County to increase downstream releases into Arroyo Grande Creek. The County is appealing the ruling. The additional downstream releases required by the preliminary injunction are detrimental to the resiliency of the water supply portfolios of Zone 3 contractors and to the goal of sustainable management of groundwater through periods of drought in the NCMA. The County has support from the NCMA and other Zone 3 agencies , the California Farm Bureau, the San Luis Obispo Farm Bureau, the California State Association of Counties, the Pacific Legal Foundation, and numerous other entities. Legal proceedings will continue into the year 2025.

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SECTION 7: Management Activities
The NCMA and overlying private well users have actively managed surface water and groundwater resources in the area for more than 40 years. Management objectives and responsibilities were first established in the 1983 Gentlemen’s Agreement, recognized in the 2002 Groundwater Management Agreement, and affirmed in the 2002 Settlement Agreement. The responsibility and authority of the Northern Parties for NCMA groundwater management was formally established through the 2002 Settlement Agreement, 2005 Stipulation, and 2008 Judgment. Throughout the long history of collaborative management, which was formalized through the Agreement, Stipulation, and Judgment, the overall management goal for the NCMA agencies is to preserve the long-term integrity of water supplies in the NCMA portion of the SMRVGB.

7.1 Strategic Plan

7.1.1 Purpose and Background
An NCMA Strategic Plan was first developed in 2014 to provide the NCMA TG with a mission statement to guide future initiatives, provide a framework for identifying and communicating water resource planning goals and objectives, and formalize a 10-year work plan for implementation of those efforts (WSC, 2014). Several key objectives were identified related to enhancing water supply reliability, improving water resource management, and increasing effective public outreach. Implementation of some of these efforts continued throughout 2024. Several key strategies were identified by the TG for improving the sustainability of the water resource. Strategic initiatives were then developed for each key strategy. The TG then developed an implementation plan for the key strategies that include current, short-term, and long-term time frames for initiatives that could be completed within 1 year, 5 years, and more than 5 years.

An update of the 2014 NCMA Strategic Plan began in 2019 and was completed in March 2020 with the publication of the Strategic Plan for the NCMA TG. The Strategic Plan was developed over a series of strategic planning sessions and NCMA TG meetings. Work began in 2024 to update the 2020 Strategic Plan, which is anticipated to be completed in the first half of 2025.

7.1.2 Mission Statement
Through the strategic planning process, the NCMA TG developed the following mission statement to guide ongoing initiatives and plan implementation and capture the requirements outlined in the 1983 Gentlemen’s Agreement, 2005 Stipulation, and the 2008 Judgment:

7.1.3 Objectives of the NCMA TG
Through the 2020 strategic planning process, the NCMA TG identified several key objectives to guide future efforts. These objectives include the following:

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A.Enhance Water Supply Reliability
Develop coordinated response plan for saltwater intrusion and other supply emergencies Support implementation of Central Coast Blue
Prepare the Northern Cities for prolonged drought conditions Analyze impacts of pumping on the groundwater basin
Improve protection against threats to groundwater sustainability B.Improve Water Resource Management
Improve management/conjunctive use of water resources
Improve coordination between technical/legal/managerial initiatives Abide by the legal/regulatory groundwater management requirements Increase understanding of current and historical groundwater conditions to inform water resources initiatives
C. Increase Effective Outreach
Engage agriculture stakeholders
Improve cooperation, coordination, and information sharing with local and regional agencies to further the objectives of the NCMA agencies
Reinforce the role of the NCMA TG as the recognized technical expert for water resources within the Northern Cities Management Area
Increase communication with City Councils and the Board of Directors Maintain equity among all NCMA agencies

7.1.4 Strategic Initiatives and Implementation Plan
Fifteen key strategies were identified by the TG for improving the sustainability of the water resource. Strategic initiatives were then developed for each key strategy, and an extensive screening and objective ranking process was applied. Utilizing the ranked and grouped strategic initiatives, the NCMA TG developed an implementation plan for the key strategies.

The implementation plan includes a ranking for each initiative, the key participants, the required actions, an estimated budget, and an implementation time frame. The implementation time frame incorporates three periods: a current designation that refers to initiatives that the NCMA plans to complete within 1 year, a short- term designation that refers to initiatives that could be completed within 5 years, and a long-term designation that refers to initiatives that are anticipated to take longer than 5 years to implement.

7.2 Management Objectives
In addition to the Strategic Plan, the NCMA TG has, over the years, established eight basic Water Management Objectives for ongoing NCMA groundwater management. Many of these objectives were incorporated into the Strategic Plan but are repeated here because they form the framework for long-term strategies and objectives to effectively manage the groundwater resource. The management objectives include the following:

1. Share Groundwater Resources and Manage Pumping

2.Enhance Management of NCMA Groundwater

3.Monitor Supply and Demand and Share Information

4. Manage Groundwater Levels and Prevent Seawater Intrusion

5.Protect Groundwater Quality

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6.Manage Cooperatively

7.Encourage Water Conservation

8.Evaluate Alternative Sources of Supply
Each of these objectives is discussed in the following sections. Under each objective, the NCMA TG has identified strategies to meet the objectives. These strategies are listed and then discussed under each of the eight objectives listed below. Other potential objectives are outlined in the final section.

7.2.1 Share Groundwater Resources and Manage Pumping
Strategies:
Continued reduction of groundwater pumping; maintain pumping below safe yield. Coordinated delivery of Lopez Lake water to the maximum amount available. Continue to import SWP supplies to OCSD and Pismo Beach. Maintain surface water delivery infrastructure to maximize capacity. Utilize Lopez Lake to store additional SWP water within San Luis Obispo County. Utilize newly modified Zone 3 agency contracts to store unused allocated water in Lopez Reservoir.

Discussion:

Maintain Groundwater Pumping Below Accepted Basin Yield A longstanding objective of water users in the NCMA has been to cooperatively share and manage groundwater resources. In 1983, the Northern Parties mutually agreed on an initial safe yield estimate and an entitlement of pumping between the urban users and agricultural irrigation users of 57 percent and 43 percent, respectively (see Section 4.1). In this agreement, the NCMA agencies also established pumping entitlements among themselves (Section 4.1.3). Subsequently, the 2002 Groundwater Management Agreement included provisions to account for changes such as agricultural land conversions. The agreements provide that any change in the accepted safe yield based on ongoing assessments would be shared on a pro rata basis.

Pursuant to the 2005 Stipulation, the NCMA agencies conducted a water balance study to update the safe yield estimate (Todd, 2007). As a result, the NCMA agencies agreed to maintain the existing pumping entitlement among the urban users and established a consistent methodology to address agricultural land use conversion.

Maximize Delivery of Lopez Lake Water and Continue Importing State Water Project Water In addition to cooperatively sharing and managing groundwater resources, the NCMA agencies have coordinated delivery of water from Lopez Lake. At the same time, Pismo Beach and OCSD have continued to import SWP water. Both actions maximize use of available surface water supplies. In 2016, in response to the ongoing drought at that time and the threat of diminishing water supplies, Arroyo Grande approved a ballot measure authorizing the purchase of SWP water on a temporary basis and only during a declared local water emergency. That condition was not reached in 2017 nor subsequent years, and Arroyo Grande has not purchased SWP water to date.

Modified Zone 3 Agency Contracts
An initiative to modify the Zone 3 agency contracts to incorporate storage provisions was started in late 2019 and continued into 2022. By the end of 2020, the conceptual contract amendments were developed, reservoir modeling was completed, and updated contract language had been developed and reviewed by the Zone 3

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TAC. In 2021, a California Environmental Quality Act review was initiated to evaluate potential impacts of the proposed amendments. On August 11, 2022, the Zone 3 TAC voted to execute the amended and restated water supply contracts.

These contract changes allow the Zone 3 subcontractors to store their unused annual water entitlement and any surplus water they receive in Lopez Reservoir, as well as allow for in-lieu storage of SWP water. In other words, each subcontractor now has a stored water account. The purpose of these changes is to provide subcontractors greater flexibility to better manage their water supply portfolios and incentivize conservation of water during emergencies and droughts. The changes provide the subcontractors greater flexibility to use their water supplies conjunctively (i.e., to implement a balanced use of surface and groundwater supplies based on hydrologic conditions) and additionally allows subcontractors to transfer stored Lopez and SWP water amongst themselves to improve water supply availability during drought conditions and water supply resiliency for the region.

These contract changes went into effect at the end of October 2022. Although existing Lopez Surplus water for each contractor was converted into Lopez Stored water as a one-time deal upon contract execution, all the Lopez Stored water and a minor amount of Stored SWP was lost during the prolonged spill event that occurred from March through June 2023. Similarly, by the end of March 2024, Zone 3 agency stored water totaled approximately 2,533 AF. However, the stored water was lost during the spill event that occurred from February through June 2024.

7.2.2 Enhance Management of NCMA Groundwater
Strategies:
Utilize the groundwater model for predictive simulations to support adaptive management of the groundwater resource.
Coordinate with the County and NMMA to develop new monitoring well(s) in key locations within the SMRVGB.
Develop a Salt and Nutrient Management Plan (SNMP) for the NCMA/NMMA. Develop and implement a framework for groundwater storage/conjunctive use, including return flows. Update the 2002 Groundwater Management Agreement.

Discussion:

The NCMA agencies participated in the oversight of the performance of the SMRVGB characterization study (Fugro, 2015) that was finalized with the distribution of the complete data sets in March 2016. The project was conducted as part of the County IRWMP 2014 update, in part to prepare for and to provide the foundational data for development of a numerical groundwater flow model and preparation of a basin-wide SNMP. To date, the SNMP has not been initiated, but the groundwater flow modeling work has been completed through Phase 1C, as described below. This groundwater flow model was developed as a part of the planning for Central Coast Blue, a recycled water project formerly known as the Regional Groundwater Sustainability Project. As part of Central Coast Blue planning and technical studies, a localized groundwater flow model (the Phase 1A model) was developed for the northern portion of the NCMA that evaluated the concept of injecting APW into the aquifer to increase recharge, improve water supply reliability, and help prevent future occurrences of seawater intrusion.

Based on the results of the Phase 1A model and through funding by SSLOCSD Supplemental Environmental Program, work was initiated in 2017 for the development of the Phase 1B groundwater flow model. The model

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domain of the Phase 1B model covers the entire NCMA, NMMA, and the portion of the SMVMA north of the Santa Maria River. The initial purpose of the Phase 1B model and the subsequently refined Phase 1C model (see Section 1.7.3) was to evaluate additional groundwater injection and extraction scenarios to further support planning for Central Coast Blue. The Phase 1C model, developed in 2021, was utilized to identify the locations of the proposed injection wells, quantify the amount of water that can be injected, evaluate strategies for preventing seawater intrusion, and develop estimates of the overall yield that the Central Coast Blue project would produce.

On March 18, 2024, the CCBRRWA Board of Directors received an update on project costs, funding, and financing for the proposed Central Coast Blue Project. Increases in Project costs, an unexpected loss of state grant funding, and improvements in local water supply conditions have prompted leaders to pause Project design and permitting until the impacts of these recent developments can be evaluated (CCBRRWA, 2024).

In response to these funding challenges, the partner agencies will re-evaluate their current water supply needs and consider project alternatives. The agencies and management team are exploring recycled water project options that would reduce costs, and leaders are advocating to secure additional grants. As a result, project construction – initially planned to break ground in summer 2024 – has been delayed (CCBRRWA, 2024).

In 2023 the NCMA TG indicated their desire to utilize the Groundwater Model for regular forward simulations to assist with adaptive management and planning for groundwater use in the basin. This would enable the TG to use the model to evaluate anticipated future conditions annually as described in the Adaptive Management Plan. To facilitate this plan, the model was updated from December 2016 to March 2024 (an addition of 87 stress periods) so that current conditions are represented. Work on the model update began in 2024 (and was completed in 2025). Details and objectives for predictive groundwater model simulations will be developed by the TG.

As part of the SLOFCWCD’s SMRVGB characterization study (Fugro, 2015), continuous monitoring transducers were installed in 2015 in coastal sentry wells 36L01 and 36L02 (which are part of the NCMA Monitoring Program) and in wells 11N/36W-12C01 and 11N/36W-12C02 (located in the NMMA and monitored by the County and by NMMA). As a result, continuous water level and field-parameter water quality data are collected from these wells.

Throughout 2022, the TG discussed various components and approaches to updating the 2002 Groundwater Management Agreement. A draft Groundwater Management Agreement update was produced in 2023 but was not finalized pending the completion of a companion Adaptive Groundwater Management Plan. Work on the Adaptive Groundwater Management Plan and finalization of the updated Groundwater Management Agreement continued in 2024. The TG anticipates finalizing the NCMA Adaptive Groundwater Management Plan and Management Agreement in 2025.

The monthly NCMA TG meetings provide for collaborative development of joint budget proposals for studies and plans and shared water resources. In addition, the monthly meetings provide a forum for discussing the data collected as part of the quarterly monitoring reports.

7.2.3 Monitor Supply and Demand and Share Information
Strategies:
Develop a Water Supply, Production, and Delivery Plan (WSPDP). In conjunction with and through the umbrella of the Zone 3 agencies and SLOFCWCD, continue efforts to evaluate potential drought emergency options and implement drought emergency actions.

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Develop a coordinated Water Shortage Contingency Plan to respond to a severe water shortage condition in the NCMA.
Share groundwater pumping data at monthly NCMA TG meetings. Evaluate future water demands through comparison with the following UWMP projections:
Arroyo Grande 2022 UWMP (WSC, 2023)
Pismo Beach 2020 UWMP (WSC, 2021)
Grover Beach 2020 UWMP (MKN, 2021)
OCSD is not required to prepare a UWMP because the community population does not meet the minimum requirement threshold.

Discussion:

Water Supply, Production and Delivery Plan
In January 2015, the NCMA agencies developed a WSPDP that applies the strategic objectives to the various supplies available to the area. The NCMA area receives supplies from Lopez Lake, the SWP, and the SMRVGB.

The purpose of the WSPDP is to provide the NCMA agencies with a delivery plan that optimizes use of existing infrastructure and minimizes groundwater pumping from the SMRVGB. The plan includes the development of a water supply and delivery modeling tool for the NCMA agencies, evaluation of three delivery scenarios, and development of recommendations for water delivery.

The WSPDP made recommendations that were implemented or subject to further study. Components of the WSPDP and the various recommendations incorporated into the Plan are summarized throughout Section 7.

The recommendations of the WSPDP reinforce the ongoing management efforts by the NCMA and provide potential projects to improve water supply reliability and protect water quality during periods of drought.

Ongoing work to implement the recommendations includes evaluation of additional delivery facilities to add operational flexibility to ensure optimum use of all supplies.

Implementing the WSPDP has allowed the NCMA to minimize the use of groundwater thereby protecting against seawater intrusion while meeting the needs of its customers and other water users.

The WSPDP now provides a framework for the NCMA to manage the groundwater resource actively and effectively, particularly in years of below-normal rainfall and below “normal” SWP delivery schedules. The WSPDP outlines a strategy to provide sufficient supplies to NCMA water users in instances of reduced SWP delivery.

Seawater intrusion is the most important potential adverse impact for the NCMA agencies to consider in their efforts to effectively manage the aquifer. Seawater intrusion, a concern since the 1960s, would degrade the quality of water in the aquifer and potentially render portions of the SMRVGB unsuitable for groundwater production (DWR, 1970).

A Deep Well Index of the three primary deep sentry wells of 7.5 feet above 0.0 feet (NAVD 88) has been recognized as the threshold, above which it is thought that there is sufficient fresh water (groundwater) outflow to prevent seawater intrusion. Inspection of the Deep Well Index in 2008–2009, before the period of water quality degradation in wells 30N03 and 30N02, shows that the Deep Well Index dropped below the 7.5-foot trigger value and remained below that level for almost 2 years. Since 2011, the Deep Well Index dropped several times below the threshold, but usually for only a few months at a time.

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Since the beginning of 2023, the Deep Well Index has been above the threshold of 7.5 feet above 0.0 feet (NAVD 88). In 2024, the Deep Well Index started the year with an index value of more than 12 feet in January.

The index value continued to climb through April, peaking at 13.8 feet, and then generally declined the remainder of the year, finishing the year at about 11 feet (NAVD 88) (Figure 12, on page 34).

Zone 3 Extended Drought Emergency Options
Management activities have become more closely coordinated among the NCMA agencies as a result of the 2011 through 2015 drought. In particular, the implementation of the LRRP limited municipal diversions and downstream releases from Lopez Lake to ensure that water is available for future potentially dry years. In addition, the Zone 3 agencies (which include the NCMA agencies) initiated a long-term drought planning effort.

The planning effort is intended to prepare water supplies for periods of extended drought conditions.

The NCMA agencies, in conjunction with the other Zone 3 agencies and SLOFCWCD, continue efforts to evaluate potential drought emergency options and implement drought emergency actions. This initiative includes identification, evaluation, and ranking of potential options available to Zone 3 to improve the reliability of its water supplies. The Zone 3 agencies and the County have pledged to work collaboratively to continue to evaluate and implement emergency water supply reliability options as required in conditions of extended drought.

Cloud seeding operations were conducted during the 2022/2023 winter season using ground-based equipment to enhance precipitation in the Lopez Lake drainage. The formal operational period began December 1, 2022 and ended March 31, 2023. However, the seeding program was suspended following a heavy rainfall event on January 9, 2023. Although there were discussions about possible seeding operations later in the season, the program remained suspended as flooding concerns continued during subsequent storm events through the remainder of the season. No cloud seeding activities occurred in 2024.

Additional potential drought emergency options that the Zone 3 agencies have evaluated in the past few years include the following:
State Water Project. Maximize importation of SLOFCWCD SWP supplies, including subcontractor supplies and the large amount of unsubscribed Table A allocation. Surplus Nacimiento Water Project (NWP) Water. Investigate transfer/exchange opportunities to obtain surplus NWP water for the Zone 3 agencies (i.e., exchange agreements with the City of San Luis Obispo and the Chorro Valley pipeline SWP subcontractors).
Water Market Purchases. Investigate opportunities to obtain additional imported water and deliver it to the Zone 3 agencies through the SWP infrastructure (e.g., exchange agreements with San Joaquin/Sacramento Valley farmers, water broker consultation, groundwater banking exchange agreements, and others).
Land Fallowing. Evaluate potential agreements with local agriculture representatives to offer financial incentives to fallow land within the Arroyo Grande and Cienega Valleys to make that irrigation water available for municipal use.
Enhanced Conservation. Evaluate opportunities for enhanced water conservation by the Zone 3 agencies (e.g., water rationing, no outdoor watering, agriculture water restrictions) to preserve additional water. Nacimiento/California Men’s Colony Intertie. Complete design of a pipeline that would connect the NWP pipeline to the California Men’s Colony Water Treatment Plant. Investigate opportunities for Zone 3 agencies to purchase NWP water and use exchange agreements and existing infrastructure to deliver additional water to Zone 3 through the Coastal Branch pipeline.

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Urban Water Management Plans
Arroyo Grande completed their 2022 UWMP32 in June 2023. Pismo Beach and Grover Beach have each completed their 2020 UWMPs in June and December 2021, respectively. OCSD is not required to prepare an UWMP because the community population does not meet the minimum requirement threshold; however, many of the aspects of a UWMP are addressed through OCSD’s participation in the NCMA planning process. New to the 2020 UWMP update cycle, water suppliers are required to prepare a standalone Water Shortage Contingency Plan (WSCP) that can be updated independently of the UWMP. A WSCP documents a supplier’s plans to manage and mitigate an actual water shortage condition, should one occur because of drought or other impacts on water supplies.

Coordinated and Shared Data
Regular monitoring of activities that affect the groundwater basin and sharing of that information have occurred for many years. The monitoring efforts include gathering data on hydrologic conditions, water supply and demand, and groundwater pumping, levels, and quality. The current monitoring program is managed by the NCMA agencies in accordance with the 2005 Stipulation and the 2008 Judgment, guided by the July 2008 Monitoring Program for the NCMA. The monitoring data and a summary of groundwater management activities are summarized in the annual reports. Arroyo Grande, Grover Beach, and Pismo Beach have each evaluated their future water demands as part of their respective UWMPs. The NCMA shares information with the two other management areas (NMMA and SMVMA) through data exchange throughout the annual report preparation cycle.

7.2.4 Manage Groundwater Levels and Prevent Seawater Intrusion Strategies:
Use stormwater ponds to capture stormwater runoff and recharge the groundwater basin. Install pressure transducers equipped with conductivity probes in key monitoring wells to provide continuous groundwater elevation and specific conductivity data. The following wells have transducers:
24B03 (North Beach Campground) 33
30F03 (Highway 1) 33
30N02 (Pier Avenue) 33
36L01 (Oceano Dunes)
36L02 (Oceano Dunes)
32C03 (County Monitoring Well No. 3)
Collect and evaluate daily municipal pumping data to determine the impact on local groundwater elevation levels.

Discussion:

Prevention of seawater intrusion through the management of groundwater levels is essential to protect the shared resource. The NCMA agencies increase groundwater recharge with stormwater infiltration and closely monitoring groundwater levels and water quality in sentry wells along the coast. 32 Although labeled 2022, this UWMP was prepared under guidance from DWR’s 2020 UWMP Guidebook. 33 The transducers in each of these Deep Index Wells were outfitted with telemetry in October 2022. This upgrade provides real-time monitoring of groundwater elevations and specific conductivity in each of these wells allowing for informed, timely decision-making regarding the management NCMA groundwater resources.

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Arroyo Grande and Grover Beach each maintain stormwater retention ponds within their jurisdictions; the SLOFCWCD maintains the stormwater system, including retention ponds, in OCSD. These ponds collect stormwater runoff, allowing them to recharge the underlying aquifers. There are approximately 140 acres of detention ponds in Arroyo Grande and 48 acres of detention ponds in Grover Beach. The stormwater detention pond in OCSD is approximately one-half acre. Grover Beach modified its stormwater system in 2012 to direct additional flow into one of its recharge basins. Because of its topography, lack of available space and proximity to the ocean, Pismo Beach does not have any stormwater retention ponds for the purpose of groundwater recharge.

The San Luis Obispo County Stormwater Resource Plan (stormwater Resource Plan) (SLO Co., 2019) was submitted to the State Water Resources Control Board for review on February 28, 2019; final approval of the plan was attained on February 25, 2020. The purpose of the Stormwater Resource Plan is to identify and prioritize stormwater and dry weather runoff capture projects in the County through detailed analyses of watershed conditions and processes, surface and groundwater resources, and the multiple benefits that can be achieved through stormwater-related capital projects and other programmatic actions (SLO Co., 2019). The Stormwater Resource Plan identifies four proposed projects within the NCMA, including the Pismo Preserve Roads Improvement Project, the Oceano Drainage Improvement Project (which was completed in 2020), South Halcyon Green/Complete Street, and a stormwater infiltration basins project. In 2019, OCSD started designing the Oceano Stormwater Capture and Groundwater Recharge Project. Construction on this project began November 2023 and was completed in November 2024. These projects emphasize water supply augmentation, environmental restoration and other community benefits, including an estimated annual infiltration capacity of 26 AF and an instantaneous floodwater capture capacity of 3.37 AF (SLO Co., 2019).

Although closely related to the objectives to manage pumping, monitor supply and demand, and share information, this objective to manage groundwater levels and prevent seawater intrusion also specifically recognizes the proximity of production wells to the coast and the threat of seawater intrusion. The NCMA agencies and SLOFCWCD have long cooperated in the monitoring of groundwater levels, including quarterly measurement by the NCMA of groundwater levels in sentry wells at the coast. Upon assuming responsibility for the coastal monitoring wells, the NCMA became aware of the need to upgrade the condition of the sentry wells. In July 2010, the wellheads (surface completions) at the four sentry monitoring well clusters in the NCMA were renovated (Todd, 2010). The renovations included raising the elevations of the top of each individual well casing by 2 to 3 feet and resurveying relative to the NAVD 88 standard in late September 2010 (Wallace Group, 2010). The individual well casings are now above the ground surface and protective locking steel risers enclose each cluster. As a result of this work, the sentry wells in the NCMA are now protected from surface contamination and tampering.

Quarterly measurement of groundwater levels aids in assessing the risk of seawater intrusion along the coast.

To enhance the data collection and assessment efforts, the NCMA installed pressure transducers equipped with conductivity probes in four of the key sentry monitoring wells (24B03, 30F03, 30N02, and 24B01) to provide continuous groundwater levels at key locations (the transducer in the shallow completion 24B01 was later removed). By combining these data with the collection and evaluation of daily municipal pumping data, the NCMA is better able to determine the response of local groundwater levels to extractions and, therefore, can better manage the aquifer and NCMA portion of the SMRVGB. In October 2022, telemetry was added to the transducers in the wells that make up the Deep Well Index (24B03, 30F03, and 30N02). The addition of telemetry allows for real-time monitoring of groundwater elevations and specific conductivity in these wells.

A pressure transducer equipped with a conductivity probe was installed in County Monitoring Well #3 (32C03) in April 2012 to monitor water level fluctuation and water quality variation in the area between the NCMA and NMMA.

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In 2015, pressure transducers equipped with conductivity probes were installed in coastal monitoring wells 36L01 and 36L02 located in the Oceano Dunes. Data from the transducers in these wells are now collected on a quarterly basis along with the other sentry wells.

Additional studies to enhance basin management efforts that have been discussed by the NCMA TG include the following:
Consider implementation of a monthly groundwater elevation data analysis of the sentry wells during periods when the Deep Well Index value is below the index target of 7.5 feet above 0.0 feet (NAVD 88) for an extended period. The addition of telemetry to the transducers installed in the three Deep Index Wells (24B03, 30F03, and 30N02) has accomplished this goal.
Consider implementation of a monthly analysis of specific conductivity data from the wells with downhole transducers during periods when the Deep Well Index value is below the index target of 7.5 feet to track potential water quality degradation (an enhanced monitoring schedule of County Monitoring Well No. 3 is not necessary because background water quality does not change or fluctuate significantly). If specific conductivity data suggest water quality degradation, implement a monthly sampling and monitoring program. The addition of telemetry to the transducers installed in the three Deep Index Wells (24B03, 30F03, and 30N02) has accomplished this goal.
Assess the potential impacts on sentry well groundwater elevations from extended periods of increased groundwater pumping by conducting analytical modeling analyses to predict water level responses given certain pumping scenarios. These analyses may be applicable to scenarios of decreased SWP deliveries or short-term emergency cuts to Lopez Lake deliveries.

7.2.5 Protect Groundwater Quality
Strategies:
Perform quarterly water quality monitoring at all sentry wells and County Well No. 3. Gather continuous (every 4 hours) groundwater elevation, temperature, and specific conductivity data from select monitoring wells to track water quality indicators for seawater intrusion. Prepare an SNMP pursuant to state policy using the results of the SMRVGB characterization study (Fugro, 2015).
Consider options for a recycled water project in the management area.

Discussion:

The objective to protect groundwater quality is closely linked with the objective for monitoring and data sharing.

To meet this objective, all sources of water quality degradation, including the threat of seawater intrusion, need to be recognized. Water quality threats and possible degradation affect the integrity of the groundwater basin, potentially resulting in loss of use or the need for expensive water treatment processes. Sentry wells are monitored quarterly for water quality and data from other NCMA production wells are assessed annually.

The monitoring program includes evaluation of potential contaminants in addition to those that might indicate seawater intrusion. Temperature and specific conductivity probes have been installed in six monitoring wells to provide continuous water quality tracking for early indication of seawater intrusion.

The NCMA agencies participated in the oversight of the performance of the SMRVGB characterization study (Fugro, 2015). The project was conducted, in part, to prepare for and to provide the foundational data for preparation of a basin-wide SNMP. To date, the SNMP has not been initiated.

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On March 18, 2024, the CCBRRWA Board of Directors received an update on project costs, funding, and financing for the proposed Central Coast Blue Project. Increases in Project costs, an unexpected loss of state grant funding, and improvements in local water supply conditions have prompted leaders to stop Project design and permitting until the impacts of these recent developments can be evaluated (CCBRRWA, 2024).

7.2.6 Manage Cooperatively
Strategies:
 Conduct effective outreach to the agricultural community by enhancing coordination with local growers.  Coordinate groundwater monitoring data sharing and annual report preparation with the NCMA, NMMA, and the SMVMA.
 Encourage interagency coordination among the NCMA agencies and include the County.  Transfer stored Lopez and SWP water amongst Zone 3 subcontractors to improve water supply availability during drought conditions and water supply resiliency for the region.

Discussion:

Since 1983, NCMA management has been based on cooperative efforts of the affected parties, including the NCMA agencies, private agricultural groundwater users, the County, the SLOFCWCD, and other local and state agencies. Specifically, the NCMA agencies have limited their pumping and, in cooperation with SLOFCWCD, invested in surface water supplies to reduce groundwater pumping to not exceed the safe yield of the NCMA portion of the SMRVGB. Other organizations participate as appropriate. Each year the NCMA TG hosts a meeting with agricultural representatives from throughout the NCMA to discuss the status of the basin, present the findings of the annual report, and develop collaborative strategies for protecting the groundwater resource.

In addition to the efforts discussed in this 2024 Annual Report, cooperative management occurs through many other venues and forums, including communication by the NCMA agencies in their respective public meetings and participation in the Water Resources Advisory Committee.

The NCMA agencies participated in preparation and adoption of the 2019 update of the County IRWMP. The IRWMP promotes integrated regional water management to ensure sustainable water uses, reliable water supplies, better water quality, environmental stewardship, efficient urban development, protection of agriculture, and a strong economy. The IRWMP integrates all the programs, plans, and projects within the region into water supply, water quality, ecosystem preservation and restoration, groundwater monitoring and management, and flood management programs.

Since the 2008 Judgment, the NCMA has taken the lead in cooperative management of its management area.

The NCMA TG met monthly (at a minimum) throughout 2024 and has been a willing and active participant in the SMGBMA technical subcommittee, which first met in 2009 (the SMGBMA technical subcommittee did not meet in 2024). The purpose of the SMGBMA technical subcommittee is to coordinate efforts such as enhanced monitoring of groundwater levels and improved sharing of data among the management areas. With the current threats to water supply in all management areas, greater communication, analytical collaboration, and data sharing are encouraged, especially between NCMA and NMMA.

Actions initiated by NCMA in early 2016 resulted in increased discussion and collaboration between the NCMA and NMMA that is ongoing. The NCMA-NMMA Management Coordination Committee has met several times since 2017 to discuss items of mutual concern and develop strategies for addressing the concerns.

Another area of increased mutual collaboration between the NCMA and NMMA was the formation of a technical team, consisting of representatives from the NCMA and NMMA, to collaboratively develop a single

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data set of water level data points to prepare a consistent set of semiannual water level contour maps for the NCMA and NMMA, so that the maps from each management area would represent a mutually agreed upon condition at the NCMA/NMMA boundary. This collaboration continued throughout 2024 through continued assessment and evaluation of the water level database, sharing of new data, and discussions of knowledge of hydrogeologic conditions gained. The result has been a series of groundwater elevation contour maps of both the NCMA and the NMMA that reflect water level conditions at the NCMA/NMMA boundary.

A Modeling Subcommittee, composed of representatives from the NCMA and NMMA, was formed to discuss the development of a numerical groundwater flow model of the portion of the SMRVGB north of the Santa Maria River. When the Phase 1B groundwater flow model project was initiated in 2017, representatives from this subcommittee formed a technical review and advisory committee to provide input to the modeling consultant and monitor progress. An NMMA representative participated in the technical review and in an advisory capacity throughout the development of the Phase 1B model. The Modeling Subcommittee has not met since completion of the Phase 1B modeling project.

An initiative to modify the Zone 3 agency contracts to incorporate storage provisions was started in late 2019.

On August 11, 2022, the Zone 3 TAC voted to execute the amended and restated water supply contracts. The new contracts went into effect at the end of October 2022. These contract changes allow the Zone 3 subcontractors to store their unused annual water entitlement and any surplus water they receive in Lopez Reservoir, as well as allow for in-lieu storage of SWP water. The changes provide the subcontractors greater flexibility to use their water supplies conjunctively (i.e., to implement a balanced use of surface and groundwater supplies based on hydrologic conditions) and additionally allows subcontractors to transfer stored Lopez and SWP water amongst themselves to improve water supply availability during drought conditions and water supply resiliency for the region.

7.2.7 Encourage Water Conservation
Strategies:
Share updated water conservation information.
Implement UWMPs.

Discussion:

Water conservation, or water use efficiency, is linked to the monitoring of supply and demand and the management of pumping. Water conservation reduces overall demand on all sources, including groundwater, and supports management objectives to manage groundwater levels and prevent seawater intrusion. In addition, water conservation is consistent with state policies seeking to achieve a 20 percent reduction in water use by the year 2020 (DWR et al., 2010). Water conservation activities in the NCMA are summarized in various documents produced by the NCMA agencies, including the 2022 UWMP32 of Arroyo Grande (WSC, 2023) and the 2020 UWMPs of Pismo Beach (WSC, 2021) and Grover Beach (MKN, 2021). (OCSD is not required to prepare an UWMP.)
The water conservation measures instituted by each NCMA agency are summarized below.

Arroyo Grande
On March 28, 2023, The Arroyo Grande City Council adopted a Resolution rescinding the declaration of a Stage 1 Water Shortage Emergency and related water shortage restrictions and penalties. A Stage 1 emergency had been declared on October 12, 2021 as a result of the ongoing severe drought conditions, declining groundwater levels, low Lopez Lake levels and resulting reductions in deliveries of water from Lopez Lake.

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As of March 14, 2023, the United States Drought Monitor showed San Luis Obispo County as no longer in a drought (as was identified in September 2021), nor abnormally dry (as was identified in February 2023) and the Stage 1 emergency declaration was rescinded.

Mandatory water conservation measures that remain in place include the following:
Use of water that results in excessive gutter runoff is prohibited. No water will be used for cleaning driveways, patios, parking lots, sidewalks, streets, or other such use except where necessary to protect the public health and safety. Outdoor water use for washing vehicles shall be attended and have hand-controlled watering devices, typically including spring-loaded shutoff nozzles.
Outdoor irrigation is prohibited between 10 a.m. and 4 p.m. Irrigation of private and public landscaping, turf areas, and gardens is permitted at even-numbered addresses only on Mondays and Thursdays, and at odd-numbered addresses only on Tuesdays and Fridays.
No irrigation of private and public landscaping, turf areas, and gardens is permitted on Wednesdays.

Irrigation is permitted at all addresses on Saturdays and Sundays. In all cases, customers are directed to use no more water than necessary to maintain landscaping. Emptying and refilling swimming pools and commercial spas are prohibited except to prevent structural damage and/or to provide for the public health and safety. Use of potable water for soil compaction or dust control purposes in construction activities is prohibited.

To help manage the use of water, the City offers water conservation incentive programs designed to decrease overall water use. The conservation and incentive programs include the following:
Cash for Grass. This program reimburses residents $1 per square foot of turf removed with a minimum of 500 square feet of turf removed and a maximum of 5,000 square feet of turf removed. Turf must be replaced with drought-tolerant plans, permeable mulch or artificial turf. Applicants are required to remain in compliance with the program’s terms and conditions for a five year period following the rebate. Plumbing Retrofit Program. This program includes installation or adjustment of showerheads, toilets, faucet aerators, and pressure regulators for single-family and multi-family residential units constructed before 1992. This program has been in place since 2004 at an expense to the City of more than $1.55 million.
Water-Wise Landscaping Program. This program provides resources for designing and installing water- wise landscaping in San Luis Obispo County, selecting climate-appropriate plants, and irrigation and drainage improvements that will help residents improve their landscaping and protect the watershed. Washing Machine Rebate. This program pays water customers a one-time $200 rebate for the installation of a certified water-efficient washing machine.
Mandatory Plumbing Retrofit. Upon change of ownership of any residential property, the seller must retrofit the property’s plumbing fixtures to meet defined low-water-use criteria. Water Conservation Hotline.

As required in the 2020 UWMP update cycle, Arroyo Grande prepared a standalone WSCP that can be updated independently of the UWMP. As droughts and other events impacting water supply occur more frequently and intensely, the WSCP helps prepare for and respond to water shortages. The WSCP includes six stages of action.

Each stage relates a supply reduction range to an associated demand reduction target, which may vary based

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on the nature of triggering conditions that are dependent on the cause, severity, and anticipated duration of the water supply shortage. Each year City staff assesses their current water supply and estimates the available future supply based on SMRVGB groundwater levels, and storage levels at Lopez Lake. If the projected supply will not meet demand, then City staff presents status to the City Council and makes recommendations to enact shortage response actions and building restrictions as needed to accommodate the reduced supply.

Pismo Beach
In 2014, Pismo Beach introduced the first-in-the-state waterless urinal mandate and a 0.5-gallon per minute (gpm) restroom aerator retrofit requirement. The components of this program include the following:
Waterless Urinal Retrofits. All existing urinals in the City were retrofitted to waterless urinals before February 14, 2016.
Faucet Aerators. New residential restroom construction requires faucets that are fitted with aerators that emit no more than 0.5 gpm. Restroom faucets in all publicly accessible restrooms, including those in hotel rooms, lobbies and restrooms, restaurants, schools, commercial and retail buildings, public buildings, and similar publicly accessible restrooms were retrofitted to install aerators that emit no more than 0.5 gpm. Sub-meters in New Construction. All new multi-unit buildings, regardless of proposed use, were required to have a separate sub-meter capable of measuring the water use of every usable unit, separate common space, and landscaping that is expected to use at least 25 gallons of water per day on average for the course of a year, regardless of the overall size of the building. Buildings that have a separate water meter for each unit are exempt.

Also in 2014, Pismo Beach adopted several Water Conservation Incentive Programs to help reduce water consumption and ensure a reliable future water supply. On February 2, 2021, the Pismo Beach City Council updated the Water Conservation Incentive Programs list to include the following:
Cash for Grass. This program reimburses residents for each square foot of lawn removed (minimum 300 square feet) and replaced with drought-tolerant landscaping, which is required to have an automatic timer and drip or micro-spray irrigation.
Water-Wise Landscaping Program. This program provides resources for designing and installing water- wise landscaping in San Luis Obispo County, selecting climate-appropriate plants, and irrigation and drainage improvements that will help residents improve their landscaping and protect the watershed. High Efficiency Toilet Rebate Program. This program provides a one-time rebate for each 3.5-gallon-per- flush or higher toilet replaced with a 1.28-gallon-per-flush or lower toilet. Water Conservation Website.

In January 2017, Pismo Beach adopted an updated schedule of development impact fees to include new recycled water fees for all new development, redevelopment, and additions to existing buildings that create additional dwelling units or additional non-residential floor area, to help fund the cost of the Central Coast Blue project.

In June 2017, in response to the State of California action to lift the drought emergency and State-mandated water use restrictions throughout the state, Pismo Beach declared a “Normal Water Supply” and adopted an Urgency Ordinance O-2017-003, revising the restrictions associated with each water supply status to conform to State mandates.

On May 18, 2022, Pismo Beach City Council adopted an urgency ordinance, which prohibits the installation of new, irrigated turf for all development.

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On March 21, 2023, Pismo Beach City Council rescinded the previously declared Critical Water Supply condition by declaring a Normal Water Supply Condition. The water use restrictions associated with the Normal Water Supply Condition are:
Use of water which causes runoff onto adjacent properties, non-irrigated areas, private and public walkways, roadways, gutters, parking lots or structures is prohibited. Outdoor water use for washing vehicles, boats, paved surfaces, buildings, and similar uses shall be attended and have hand-controlled water devices, which shut off the water immediately when not in use. No water shall be used for cleaning driveways, patios, parking lots, sidewalks, streets, or other such uses except as found necessary by the city to protect the public health or safety. Outdoor irrigation
Outdoor irrigation is prohibited between the hours of 10 a.m. and 4 p.m. Applying water to outdoor landscapes during and within 48 hours after measurable rainfall is prohibited.
Restaurants shall serve drinking water only in response to a specific request by a customer. Using water in a fountain or other decorative water feature, except where the water is part of a recirculating system, is prohibited.

As required in the 2020 UWMP update, Pismo Beach prepared a standalone WSCP that can be updated independently of the UWMP. As droughts and other events impacting water supply occur more frequently and intensely, the WSCP helps prepare for and respond to water shortages. The WSCP includes six standard stages of action tied to actual water shortage conditions in 10 percent increments. Each stage relates a supply reduction range to an associated demand reduction target, which may vary based on the nature of triggering conditions that are dependent on the cause, severity, and anticipated duration of the water supply shortage.

Each year City staff assesses their current water supply and estimates the available future supply based on their SWP Table A allocation, the SMRVGB groundwater levels, and storage levels at Lopez Lake. If the projected supply will not meet demand, then City staff presents status to the City Council and makes recommendations to enact shortage response actions and building restrictions as needed to accommodate the reduced supply (WSC, 2021).

On November 15, 2022, the Pismo Beach City Council directed staff to work with the SLOFCWCD to increase the Pismo Beach SWP drought buffer to 3,192 AFY. City staff has had initial conversations with SLOFCWCD staff; however this drought buffer increase is still pending as of the date of this report.

Grover Beach
On March 13, 2023, Grover Beach City Council rescinded the previously declared Stage III Water Shortage Condition and declared a Stage I condition (the lowest of 6 possible conditions set forth in the Grover Beach WSCP). Although not enforced during Stage I conditions, the following water use restrictions remain in place:
Washing of sidewalks, driveways, or roadways where air blowers or sweeping provides a reasonable alternative.
Refilling of private pools except to maintain water levels. Planting of turf and other new landscaping, unless it consists of drought-tolerant plants. Washing vehicles, boats, etc. without a quick-acting shut-off nozzle on the hose. Washing any exterior surfaces unless using a quick-acting shut-off nozzle on the hose. Restaurant water service, unless requested.

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Use of potable water for construction purposes, unless no other source of water or method can be used. Operation of ornamental fountain or car wash unless water is re-circulated.

In 2020, Grover Beach made changes to its water conservation program through preparation and adoption of a WSCP,34 enacted when water supplies are insufficient to support demand. As droughts and other events impacting water supply occur more frequently and intensely, the WSCP helps prepare for and respond to water shortages. The changes include 6 stages of action tied to actual water shortage conditions in 10 percent increments. Each stage relates a supply reduction range to an associated demand reduction target, which may vary based on the nature of triggering conditions that are dependent on the cause, severity, and anticipated duration of the water supply shortage. Grover Beach city staff continuously monitor the availability of water supply sources 35 and, if one or more set of triggering conditions are met, the Public Works Director notifies the City Council and recommends declaration of the appropriate stage of water shortage.

In addition to the voluntary water use restrictions, Grover Beach has implemented water conservation incentive programs including the following:
Cash for Grass Rebate Program
Smart Irrigation Controller and Sensor Rebate Program
Toilet Fixture, Showerhead, and Sink Aerator Retrofit Rebate Program Washing Machine Rebate Program
OCSD
Given the population of its service area, OCSD is not required to prepare an UWMP nor was it required to reduce water consumption as mandated by the Governor for urban water suppliers during the recent drought.

Outdoor water use restrictions have been adopted, as required. In April 2015, OCSD adopted a rate increase that included tiered rates to promote water conservation. These rates were reduced in July 2017, upon adoption of the Post Drought Consumption Charges and Supplemental Water Charge Ordinance. In October 2020, the OCSD increased water rates and a new water rate structure was adopted that reduced the number of consumption tiers from five to two. This brought the OCSD rates more closely into conformance with Proposition 218 requirements. The Tier 1 rate is tied directly to the cost of the Lopez Water supply and the Tier 2 rate is tied directly to the cost of the State Water supply. In addition, the new rate structure eliminated the six units of water previously included in the base rate so that customers now pay a consumption charge for every unit of water used, which further promotes conservation.

OCSD pumped only 1 percent of its groundwater entitlement in 2024 and is using its Lopez and SWP supplies.

OCSD’s conservation efforts realized 31 percent reductions from 2013 levels in 2024.

Strategies exist in the event of temporary non-delivery of SWP and Lopez Lake water and other unforeseen circumstances. Current strategies include resumption of groundwater pumping, storage of Lopez Lake entitlement water, and maximizing deliveries of SWP water as provided in SWP contracts. 34 The WSCP is a component of the City of Grover Beach’s 2020 UWMP (MKN, 2021). 35 Including monitoring of Lopez Lake supplies and monitoring of groundwater availability based on the Deep Well Index value as compared with its threshold value of 7.5 feet (NAVD 88).

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7.2.8 Evaluate Alternative Sources of Supply
Strategies:
Evaluate and advance the expanded use of recycled water. Analyze the capacity of the Lopez Lake and Coastal Branch pipelines to maximize deliveries of surface water. The following analyses have been completed:
Lopez Lake Pipeline Capacity Evaluation (WSC, 2011a)
Lopez Lake Pipeline Capacity Re-Evaluation (WSC, 2011b) Coastal Branch Capacity Assessment (WSC, 2011a)
Lopez Bypass and State Water Delivery Evaluation (WSC, 2017) Optimize existing surface water supplies, including surface water storage, through the development of a framework for interagency exchanges and transfers, including SWP and Lopez Lake supplies. Maximize Lopez Lake pipeline capacity.

Discussion:

The NCMA agencies continue to evaluate alternative sources of water supply that could provide a more reliable and sustainable water supply for the NCMA. An expanded portfolio of water supply sources will support sustainable management of the groundwater resource and help to reduce the risk of water shortages. These alternative sources include the following:
State Water Project. OCSD and Pismo Beach are currently SWP customers. Both agencies increased their SWP allocations by securing “drought buffers” to increase the availability of supply during periods of SWP shortfalls. Grover Beach and Arroyo Grande are not SWP customers. However, Arroyo Grande approved a measure in 2016 authorizing the City to purchase SWP water from the SLOFCWCD’s excess entitlement on a temporary basis and only during a declared local water emergency. To date, Arroyo Grande has not declared such an emergency and has not purchased SWP water. Water Recycling. As discussed in Section 7.2.5, Pismo Beach and the SSLOCSD both prepared RWFPSs to evaluate alternatives for a recycled water program that could provide a supplemental water supply source and improve the water supply reliability for the Pismo Beach and the SSLOCSD member agencies (Arroyo Grande, Grover Beach, and OCSD).

Section 7.2.5, also describes previous efforts to advance the Central Coast Blue Project, the recycled water alternative developed through the RWFPSs. Construction of a new advanced water purification facility and injection wells could allow for the use of recycled water to recharge the groundwater basin and provide a new, drought-resilient source of water supply for the area. As discussed previously, progress on Central Coast Blue as originally conceived has been suspended after increases in project costs and loss of state grant funding.

However, a comparable recycled water project with a reduced approach and costs would allow the NCMA agencies to increase recharge to the aquifer, improve water supply reliability, and help prevent future occurrences of seawater intrusion.
Lopez Lake Expansion. In 2008, the County sponsored a preliminary assessment of the concept of installing inflatable Obermeyer Gates at the Lopez Dam spillway. Subsequently, the SLOFCWCD CSA 12 and Arroyo Grande, Grover Beach, and Pismo Beach funded a study to further analyze the feasibility of increasing the yield of Lopez Lake by raising the spillway height with an inflatable dam or permanent extension. The study was finalized in 2013 and identified the potential to increase the annual yield from Lopez Lake by 500 AFY with a spillway height increase of 6 feet (Stetson, 2013). The NCMA agencies and

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Zone 3 are continuing to evaluate other aspects of the project, including impacts on the Habitat Conservation Plan process. The DWR Division of Safety of Dams requires that the dam also be raised, which likely renders this plan infeasible.
Desalination. In 2006, Arroyo Grande, Grover Beach, and OCSD used Proposition 50 funds to complete a feasibility study on desalination as an additional water supply option for the NCMA. This alternative supply is not considered to be a viable option at this time.

When PG&E announced plans to close its Diablo Canyon Power Plant, previous efforts by the SLOFCWCD to (1) evaluate the potential to expand the existing desalination facility at the PG&E Diablo Canyon Power Plant and (2) connect it to the Lopez Lake pipeline to provide a supplemental water supply for the Zone 3 agencies were terminated.
Nacimiento Pipeline Extension. In 2006, Arroyo Grande, Grover Beach, and OCSD completed an evaluation of a Nacimiento pipeline extension to determine the feasibility of delivery of water from the Nacimiento reservoir to the NCMA. This alternative supply is not considered to be a viable option at this time.

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SECTION 8: References
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CHG. 2017. Phase 1A Model TM; Groundwater Flow Analysis Regional Groundwater Sustainability Project Arroyo Grande/Tri-Cities Mesa Area. Prepared for City of Pismo Beach and Water Systems Consulting.

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CCBRRWA. 2024. Central Coast Blue Project Update News Release. Available at https://www.centralcoastblue.com/post/central-coast-blue-project-update . March 19, 2024.

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DWR. 2002. Water Resources of the Arroyo Grande – Nipomo Mesa Area: Southern District Report. Prepared by the California Department of Water Resources.

DWR. 2016. IWFM Demand Calculator IDC 2015: Theoretical Documentation and User’s Manual. Central Valley Modeling Unit. Prepared by the California Department of Water Resources Bay Delta Office.

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Mualem, Y. 1976. “A new model for predicting the hydraulic conductivity of unsaturated porous media.” Water Resources Res., 12, 513-522.

NCMA. 2009. 2008 Annual Monitoring Report, prepared by Todd Engineers for Northern Cities Management Area. April 2009.

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NCMA. 2012. 2011 Annual Monitoring Report, prepared by GEI Consultants for Northern Cities Management Area. May 2012.

NCMA. 2013. 2012 Annual Monitoring Report, prepared by GEI Consultants for Northern Cities Management Area. April 2013.

NCMA. 2014. 2013 Annual Monitoring Report, prepared by Fugro Consultants for Northern Cities Management Area. April 2014.

NCMA. 2015. 2014 Annual Monitoring Report, prepared by Fugro Consultants for Northern Cities Management Area. April 2015.

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NMMA. 2010. 2nd Annual Report, Calendar Year 2009, prepared by the Nipomo Mesa Management Area Technical Group, April 2010.

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WSC. 2021. City of Pismo Beach 2020 Urban Water Management Plan. June 2021.

WSC. 2023. City of Arroyo Grande Final 2022 Urban Water Management Plan. Prepared by Water Systems Consulting, Inc. June 2023.

Woodring, W.P and M.N. Bramlette. 1950. “Geology and Paleontology of the Santa Maria District, California.” U.S. Geological Survey, Professional Paper 222, 142 p.

Worts, G.G., Jr. 1951. “Geology and Ground-water Resources of the Santa Maria Valley Area, California.” U.S.

Geological Survey Water-Supply Paper 1000, 176 p.

APPENDIX A

NCMA Sentry Well Water Level and Water Quality Data

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Well Common Name Aquifer Date Surface
Completion RP Description RP Elev.
(feet NAVD 88)
Groundwater Elevation
(feet NAVD 88)
Depth to Water
(feet)
32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/15/2024 Stove Pipe Top of PVC Casing 13.33 7.62 5.71 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/9/2024 Stove Pipe Top of PVC Casing 13.33 7.21 6.12 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/17/2024 Stove Pipe Top of PVC Casing 13.33 7.25 6.08 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/9/2024 Stove Pipe Top of PVC Casing 13.33 7.87 5.46 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/10/2023 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/4/2023 Stove Pipe Top of PVC Casing 13.33 7.16 6.17 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/11/2023 Stove Pipe Top of PVC Casing 13.33 6.83 6.50 32S/12E-24B01 North Beach Campground - Shallow Alluvium 2/7/2023 Stove Pipe Top of PVC Casing 13.33 7.45 5.88 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/3/2022 Stove Pipe Top of PVC Casing 13.33 7.36 5.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/11/2022 Stove Pipe Top of PVC Casing 13.33 7.00 6.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/5/2022 Stove Pipe Top of PVC Casing 13.33 7.26 6.07 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/4/2022 Stove Pipe Top of PVC Casing 13.33 7.71 5.62 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/5/2021 Stove Pipe Top of PVC Casing 13.33 7.38 5.95 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/13/2021 Stove Pipe Top of PVC Casing 13.33 7.43 5.90 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/6/2021 Stove Pipe Top of PVC Casing 13.33 7.38 5.95 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/6/2021 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/7/2020 Stove Pipe Top of PVC Casing 13.33 7.31 6.02 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/6/2020 Stove Pipe Top of PVC Casing 13.33 7.64 5.69 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/17/2020 Stove Pipe Top of PVC Casing 13.33 7.65 5.68 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/7/2020 Stove Pipe Top of PVC Casing 13.33 7.78 5.55 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/9/2019 Stove Pipe Top of PVC Casing 13.33 7.36 5.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/9/2019 Stove Pipe Top of PVC Casing 13.33 7.51 5.82 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/9/2019 Stove Pipe Top of PVC Casing 13.33 7.18 6.15 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/8/2019 Stove Pipe Top of PVC Casing 13.33 7.63 5.70 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/9/2018 Stove Pipe Top of PVC Casing 13.33 7.29 6.04 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/10/2018 Stove Pipe Top of PVC Casing 13.33 6.58 6.75 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/10/2018 Stove Pipe Top of PVC Casing 13.33 7.10 6.23 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/10/2018 Stove Pipe Top of PVC Casing 13.33 7.58 5.75 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/10/2017 Stove Pipe Top of PVC Casing 13.33 7.46 5.87 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/11/2017 Stove Pipe Top of PVC Casing 13.33 6.84 6.49 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/11/2017 Stove Pipe Top of PVC Casing 13.33 7.28 6.05 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/10/2017 Stove Pipe Top of PVC Casing 13.33 8.04 5.29 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/12/2016 Stove Pipe Top of PVC Casing 13.33 7.04 6.29 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/19/2016 Stove Pipe Top of PVC Casing 13.33 6.80 6.53 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/12/2016 Stove Pipe Top of PVC Casing 13.33 7.23 6.10 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/12/2016 Stove Pipe Top of PVC Casing 13.33 8.41 4.92 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/13/2015 Stove Pipe Top of PVC Casing 13.33 7.85 5.48 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/14/2015 Stove Pipe Top of PVC Casing 13.33 7.52 5.81 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/14/2015 Stove Pipe Top of PVC Casing 13.33 7.36 5.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/13/2015 Stove Pipe Top of PVC Casing 13.33 7.75 5.58 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/14/2014 Stove Pipe Top of PVC Casing 13.33 7.82 5.51 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/29/2014 Stove Pipe Top of PVC Casing 13.33 7.59 5.74 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/4/2014 Stove Pipe Top of PVC Casing 13.33 7.06 6.27 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/15/2014 Stove Pipe Top of PVC Casing 13.33 7.63 5.70 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/14/2014 Stove Pipe Top of PVC Casing 13.33 7.83 5.50 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/14/2013 Stove Pipe Top of PVC Casing 13.33 7.51 5.82 Table A-1. NCMA Sentry Wells Water Level Data

Page 1 of 47 ends

Well Common Name Aquifer Date Surface
Completion RP Description RP Elev.
(feet NAVD 88)
Groundwater Elevation
(feet NAVD 88)
Depth to Water
(feet)
Table A-1. NCMA Sentry Wells Water Level Data
32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/9/2013 Stove Pipe Top of PVC Casing 13.33 7.49 5.84 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/10/2013 Stove Pipe Top of PVC Casing 13.33 6.58 6.75 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/14/2013 Stove Pipe Top of PVC Casing 13.33 7.86 5.47 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/29/2012 Stove Pipe Top of PVC Casing 13.33 7.66 5.67 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/23/2012 Stove Pipe Top of PVC Casing 13.33 7.79 5.54 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/18/2012 Stove Pipe Top of PVC Casing 13.33 8.00 5.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/11/2012 Stove Pipe Top of PVC Casing 13.33 7.86 5.47 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/21/2011 Stove Pipe Top of PVC Casing 13.33 7.78 5.55 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/26/2011 Stove Pipe Top of PVC Casing 13.33 7.20 6.13 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/20/2011 Stove Pipe Top of PVC Casing 13.33 7.18 6.15 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/24/2011 Stove Pipe Top of PVC Casing 13.33 7.80 5.53 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/21/2010 Stove Pipe Top of PVC Casing 13.33 7.21 6.12 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/27/2010 Stove Pipe Top of PVC Casing 13.33 7.10 6.23 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/27/2010 Stove Pipe Top of PVC Casing 13.33 6.86 6.47 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/27/2010 Stove Pipe Top of PVC Casing 13.33 7.57 5.76 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/19/2009 Stove Pipe Top of PVC Casing 13.33 8.42 4.91 32S/12E-24B01 North Beach Campground - Shallow Alluvium 8/20/2009 Stove Pipe Top of PVC Casing 13.33 7.45 5.88 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/12/2009 Stove Pipe Top of PVC Casing 13.33 7.12 6.21 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/7/2009 Stove Pipe Top of PVC Casing 13.33 9.09 4.24 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/15/2008 Stove Pipe Top of PVC Casing 13.33 5.98 7.35 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/15/2008 Stove Pipe Top of PVC Casing 13.33 8.05 5.28 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/18/2007 Stove Pipe Top of PVC Casing 13.33 5.55 7.78 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/19/2006 Stove Pipe Top of PVC Casing 13.33 9.95 3.38 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/25/2006 Stove Pipe Top of PVC Casing 13.33 7.70 5.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/7/2005 Stove Pipe Top of PVC Casing 13.33 6.40 6.93 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/29/2005 Stove Pipe Top of PVC Casing 13.33 8.05 5.28 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/29/2004 Stove Pipe Top of PVC Casing 13.33 6.00 7.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/8/2004 Stove Pipe Top of PVC Casing 13.33 9.90 3.43 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/8/2003 Stove Pipe Top of PVC Casing 13.33 9.50 3.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/14/2002 Stove Pipe Top of PVC Casing 13.33 7.10 6.23 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/9/2002 Stove Pipe Top of PVC Casing 13.33 9.90 3.43 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/5/2001 Stove Pipe Top of PVC Casing 13.33 8.00 5.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/23/2001 Stove Pipe Top of PVC Casing 13.33 8.50 4.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/24/2000 Stove Pipe Top of PVC Casing 13.33 7.20 6.13 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/29/1999 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/15/1999 Stove Pipe Top of PVC Casing 13.33 8.92 4.41 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/20/1998 Stove Pipe Top of PVC Casing 13.33 8.50 4.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/23/1998 Stove Pipe Top of PVC Casing 13.33 9.70 3.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/22/1997 Stove Pipe Top of PVC Casing 13.33 7.54 5.79 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/29/1997 Stove Pipe Top of PVC Casing 13.33 7.57 5.76 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/23/1996 Stove Pipe Top of PVC Casing 13.33 6.20 7.13 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/29/1996 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/10/1995 Stove Pipe Top of PVC Casing 13.33 7.40 5.93 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/19/1995 Stove Pipe Top of PVC Casing 13.33 8.81 4.52 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/1/1994 Stove Pipe Top of PVC Casing 13.33 6.00 7.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/11/1994 Stove Pipe Top of PVC Casing 13.33 6.74 6.59

Page 2 of 47 ends

Well Common Name Aquifer Date Surface
Completion RP Description RP Elev.
(feet NAVD 88)
Groundwater Elevation
(feet NAVD 88)
Depth to Water
(feet)
Table A-1. NCMA Sentry Wells Water Level Data
32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/13/1993 Stove Pipe Top of PVC Casing 13.33 6.75 6.58 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/8/1993 Stove Pipe Top of PVC Casing 13.33 7.81 5.52 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/4/1992 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/21/1992 Stove Pipe Top of PVC Casing 13.33 6.80 6.53 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/11/1991 Stove Pipe Top of PVC Casing 13.33 6.19 7.14 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/19/1991 Stove Pipe Top of PVC Casing 13.33 6.35 6.98 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/11/1990 Stove Pipe Top of PVC Casing 13.33 6.36 6.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/24/1990 Stove Pipe Top of PVC Casing 13.33 6.16 7.17 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/4/1989 Stove Pipe Top of PVC Casing 13.33 7.19 6.14 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/17/1989 Stove Pipe Top of PVC Casing 13.33 6.39 6.94 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/20/1988 Stove Pipe Top of PVC Casing 13.33 6.30 7.03 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/29/1988 Stove Pipe Top of PVC Casing 13.33 6.44 6.89 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/21/1988 Stove Pipe Top of PVC Casing 13.33 6.36 6.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/19/1987 Stove Pipe Top of PVC Casing 13.33 6.25 7.08 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/13/1987 Stove Pipe Top of PVC Casing 13.33 7.52 5.81 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/31/1986 Stove Pipe Top of PVC Casing 13.33 6.82 6.51 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/27/1986 Stove Pipe Top of PVC Casing 13.33 6.52 6.81 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/18/1985 Stove Pipe Top of PVC Casing 13.33 7.29 6.04 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/22/1985 Stove Pipe Top of PVC Casing 13.33 8.60 4.73 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/29/1984 Stove Pipe Top of PVC Casing 13.33 8.58 4.75 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/28/1983 Stove Pipe Top of PVC Casing 13.33 8.78 4.55 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/6/1982 Stove Pipe Top of PVC Casing 13.33 8.55 4.78 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/19/1981 Stove Pipe Top of PVC Casing 13.33 8.62 4.71 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/21/1981 Stove Pipe Top of PVC Casing 13.33 8.64 4.69 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/21/1980 Stove Pipe Top of PVC Casing 13.33 8.11 5.22 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/9/1980 Stove Pipe Top of PVC Casing 13.33 8.62 4.71 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/7/1979 Stove Pipe Top of PVC Casing 13.33 8.10 5.23 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/17/1979 Stove Pipe Top of PVC Casing 13.33 8.57 4.76 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/17/1977 Stove Pipe Top of PVC Casing 13.33 8.31 5.02 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/9/1976 Stove Pipe Top of PVC Casing 13.33 -3.30 16.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/21/1976 Stove Pipe Top of PVC Casing 13.33 6.70 6.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/14/1976 Stove Pipe Top of PVC Casing 13.33 8.70 4.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/7/1975 Stove Pipe Top of PVC Casing 13.33 8.70 4.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/1/1975 Stove Pipe Top of PVC Casing 13.33 8.62 4.71 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/7/1974 Stove Pipe Top of PVC Casing 13.33 9.70 3.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/1/1974 Stove Pipe Top of PVC Casing 13.33 8.70 4.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 9/20/1973 Stove Pipe Top of PVC Casing 13.33 8.54 4.79 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/29/1972 Stove Pipe Top of PVC Casing 13.33 8.13 5.20 32S/12E-24B01 North Beach Campground - Shallow Alluvium 2/29/1972 Stove Pipe Top of PVC Casing 13.33 9.70 3.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 2/21/1972 Stove Pipe Top of PVC Casing 13.33 9.25 4.08 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/29/1971 Stove Pipe Top of PVC Casing 13.33 8.34 4.99 32S/12E-24B01 North Beach Campground - Shallow Alluvium 8/28/1971 Stove Pipe Top of PVC Casing 13.33 8.45 4.88 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/2/1971 Stove Pipe Top of PVC Casing 13.33 8.11 5.22 32S/12E-24B01 North Beach Campground - Shallow Alluvium 3/2/1971 Stove Pipe Top of PVC Casing 13.33 8.89 4.44 32S/12E-24B01 North Beach Campground - Shallow Alluvium 12/15/1970 Stove Pipe Top of PVC Casing 13.33 8.28 5.05 32S/12E-24B01 North Beach Campground - Shallow Alluvium 8/4/1970 Stove Pipe Top of PVC Casing 13.33 7.70 5.63

Page 3 of 47 ends

Well Common Name Aquifer Date Surface
Completion RP Description RP Elev.
(feet NAVD 88)
Groundwater Elevation
(feet NAVD 88)
Depth to Water
(feet)
Table A-1. NCMA Sentry Wells Water Level Data
32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/3/1970 Stove Pipe Top of PVC Casing 13.33 8.40 4.93 32S/12E-24B01 North Beach Campground - Shallow Alluvium 3/27/1970 Stove Pipe Top of PVC Casing 13.33 8.54 4.79 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/29/1970 Stove Pipe Top of PVC Casing 13.33 8.47 4.86 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/3/1969 Stove Pipe Top of PVC Casing 13.33 8.15 5.18 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/23/1969 Stove Pipe Top of PVC Casing 13.33 7.70 5.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/24/1969 Stove Pipe Top of PVC Casing 13.33 7.70 5.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/22/1969 Stove Pipe Top of PVC Casing 13.33 7.70 5.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/18/1969 Stove Pipe Top of PVC Casing 13.33 8.57 4.76 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/15/1969 Stove Pipe Top of PVC Casing 13.33 7.99 5.34 32S/12E-24B01 North Beach Campground - Shallow Alluvium 12/12/1968 Stove Pipe Top of PVC Casing 13.33 7.89 5.44 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/14/1968 Stove Pipe Top of PVC Casing 13.33 7.70 5.63 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/17/1968 Stove Pipe Top of PVC Casing 13.33 7.23 6.10 32S/12E-24B01 North Beach Campground - Shallow Alluvium 9/14/1968 Stove Pipe Top of PVC Casing 13.33 7.06 6.27 32S/12E-24B01 North Beach Campground - Shallow Alluvium 8/13/1968 Stove Pipe Top of PVC Casing 13.33 7.47 5.86 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/22/1968 Stove Pipe Top of PVC Casing 13.33 7.02 6.31 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/24/1968 Stove Pipe Top of PVC Casing 13.33 7.00 6.33 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/30/1968 Stove Pipe Top of PVC Casing 13.33 7.01 6.32 32S/12E-24B01 North Beach Campground - Shallow Alluvium 4/20/1968 Stove Pipe Top of PVC Casing 13.33 7.86 5.47 32S/12E-24B01 North Beach Campground - Shallow Alluvium 3/21/1968 Stove Pipe Top of PVC Casing 13.33 7.71 5.62 32S/12E-24B01 North Beach Campground - Shallow Alluvium 2/22/1968 Stove Pipe Top of PVC Casing 13.33 8.03 5.30 32S/12E-24B01 North Beach Campground - Shallow Alluvium 1/16/1968 Stove Pipe Top of PVC Casing 13.33 8.36 4.97 32S/12E-24B01 North Beach Campground - Shallow Alluvium 12/8/1967 Stove Pipe Top of PVC Casing 13.33 8.04 5.29 32S/12E-24B01 North Beach Campground - Shallow Alluvium 11/13/1967 Stove Pipe Top of PVC Casing 13.33 7.71 5.62 32S/12E-24B01 North Beach Campground - Shallow Alluvium 10/11/1967 Stove Pipe Top of PVC Casing 13.33 6.84 6.49 32S/12E-24B01 North Beach Campground - Shallow Alluvium 9/5/1967 Stove Pipe Top of PVC Casing 13.33 7.35 5.98 32S/12E-24B01 North Beach Campground - Shallow Alluvium 8/8/1967 Stove Pipe Top of PVC Casing 13.33 7.13 6.20 32S/12E-24B01 North Beach Campground - Shallow Alluvium 7/12/1967 Stove Pipe Top of PVC Casing 13.33 7.01 6.32 32S/12E-24B01 North Beach Campground - Shallow Alluvium 6/1/1967 Stove Pipe Top of PVC Casing 13.33 7.50 5.83 32S/12E-24B01 North Beach Campground - Shallow Alluvium 5/2/1967 Stove Pipe Top of PVC Casing 13.33 7.60 5.73 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/15/2024 Stove Pipe Top of PVC Casing 13.41 8.21 5.20 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/9/2024 Stove Pipe Top of PVC Casing 13.41 7.39 6.02 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/17/2024 Stove Pipe Top of PVC Casing 13.41 7.93 5.48 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/9/2024 Stove Pipe Top of PVC Casing 13.41 8.81 4.60 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/10/2023 Stove Pipe Top of PVC Casing 13.41 8.04 5.37 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/4/2023 Stove Pipe Top of PVC Casing 13.41 7.26 6.15 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/11/2023 Stove Pipe Top of PVC Casing 13.41 7.33 6.08 32S/12E-24B02 North Beach Campground - Middle Paso Robles 2/7/2023 Stove Pipe Top of PVC Casing 13.41 7.77 5.64 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/3/2022 Stove Pipe Top of PVC Casing 13.41 6.79 6.62 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/11/2022 Stove Pipe Top of PVC Casing 13.41 6.24 7.17 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/5/2022 Stove Pipe Top of PVC Casing 13.41 6.54 6.87 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/4/2022 Stove Pipe Top of PVC Casing 13.41 7.85 5.56 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/5/2021 Stove Pipe Top of PVC Casing 13.41 7.02 6.39 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/13/2021 Stove Pipe Top of PVC Casing 13.41 6.48 6.93 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/6/2021 Stove Pipe Top of PVC Casing 13.41 7.33 6.08 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/6/2021 Stove Pipe Top of PVC Casing 13.41 7.31 6.10 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/7/2020 Stove Pipe Top of PVC Casing 13.41 6.94 6.47

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Well Common Name Aquifer Date Surface
Completion RP Description RP Elev.
(feet NAVD 88)
Groundwater Elevation
(feet NAVD 88)
Depth to Water
(feet)
Table A-1. NCMA Sentry Wells Water Level Data
32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/6/2020 Stove Pipe Top of PVC Casing 13.41 7.23 6.18 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/7/2020 Stove Pipe Top of PVC Casing 13.41 8.04 5.37 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/7/2020 Stove Pipe Top of PVC Casing 13.41 7.65 5.76 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/9/2019 Stove Pipe Top of PVC Casing 13.41 7.06 6.35 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/9/2019 Stove Pipe Top of PVC Casing 13.41 7.18 6.23 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/9/2019 Stove Pipe Top of PVC Casing 13.41 7.08 6.33 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/8/2019 Stove Pipe Top of PVC Casing 13.41 7.58 5.83 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/9/2018 Stove Pipe Top of PVC Casing 13.41 6.93 6.48 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/10/2018 Stove Pipe Top of PVC Casing 13.41 6.41 7.00 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/10/2018 Stove Pipe Top of PVC Casing 13.41 7.56 5.85 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/10/2018 Stove Pipe Top of PVC Casing 13.41 8.01 5.40 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/10/2017 Stove Pipe Top of PVC Casing 13.41 7.12 6.29 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/11/2017 Stove Pipe Top of PVC Casing 13.41 6.65 6.76 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/11/2017 Stove Pipe Top of PVC Casing 13.41 7.32 6.09 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/10/2017 Stove Pipe Top of PVC Casing 13.41 8.25 5.16 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/12/2016 Stove Pipe Top of PVC Casing 13.41 6.53 6.88 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/19/2016 Stove Pipe Top of PVC Casing 13.41 5.97 7.44 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/12/2016 Stove Pipe Top of PVC Casing 13.41 7.21 6.20 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/12/2016 Stove Pipe Top of PVC Casing 13.41 8.07 5.34 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/13/2015 Stove Pipe Top of PVC Casing 13.41 6.97 6.44 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/14/2015 Stove Pipe Top of PVC Casing 13.41 6.61 6.80 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/14/2015 Stove Pipe Top of PVC Casing 13.41 6.45 6.96 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/13/2015 Stove Pipe Top of PVC Casing 13.41 7.30 6.11 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/14/2014 Stove Pipe Top of PVC Casing 13.41 6.97 6.44 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/29/2014 Stove Pipe Top of PVC Casing 13.41 6.53 6.88 32S/12E-24B02 North Beach Campground - Middle Paso Robles 6/4/2014 Stove Pipe Top of PVC Casing 13.41 5.33 8.08 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/15/2014 Stove Pipe Top of PVC Casing 13.41 7.03 6.38 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/14/2014 Stove Pipe Top of PVC Casing 13.41 7.24 6.17 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/14/2013 Stove Pipe Top of PVC Casing 13.41 6.50 6.91 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/9/2013 Stove Pipe Top of PVC Casing 13.41 6.41 7.00 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/10/2013 Stove Pipe Top of PVC Casing 13.41 7.25 6.16 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/14/2013 Stove Pipe Top of PVC Casing 13.41 7.97 5.44 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/29/2012 Stove Pipe Top of PVC Casing 13.41 7.70 5.71 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/23/2012 Stove Pipe Top of PVC Casing 13.41 7.46 5.95 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/18/2012 Stove Pipe Top of PVC Casing 13.41 8.10 5.31 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/11/2012 Stove Pipe Top of PVC Casing 13.41 8.11 5.30 32S/12E-24B02 North Beach Campground - Middle Paso Robles 11/21/2011 Stove Pipe Top of PVC Casing 13.41 7.89 5.52 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/26/2011 Stove Pipe Top of PVC Casing 13.41 7.07 6.34 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/20/2011 Stove Pipe Top of PVC Casing 13.41 7.28 6.13 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/24/2011 Stove Pipe Top of PVC Casing 13.41 7.89 5.52 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/21/2010 Stove Pipe Top of PVC Casing 13.41 6.79 6.62 32S/12E-24B02 North Beach Campground - Middle Paso Robles 7/27/2010 Stove Pipe Top of PVC Casing 13.41 6.53 6.88 32S/12E-24B02 North Beach Campground - Middle Paso Robles 4/27/2010 Stove Pipe Top of PVC Casing 13.41 6.36 7.05 32S/12E-24B02 North Beach Campground - Middle Paso Robles 1/27/2010 Stove Pipe Top of PVC Casing 13.41 7.32 6.09 32S/12E-24B02 North Beach Campground - Middle Paso Robles 10/19/2009 Stove Pipe Top of PVC Casing 13.41 8.44 4.97 32S/12E-24B02 North Beach Campground - Middle Paso Robles 8/20/2009 Stove Pipe Top of PVC Casing 13.41 6.61 6.80

Page 5 of 47 ends

Pismo Beach City CouncilJuly 1, 2025

Pismo Beach City Council
July 1, 2025