San Joaquin Valley – Eastern San Joaquin
Statistics
- Basin Name
- San Joaquin Valley – Eastern San Joaquin
- Basin Number
- 5-022.01
- SGMA Basin Priority
- High
- Critically Overdrafted
- Yes
- Hydrologic Region Name
- San Joaquin River
- Counties
- Calaveras, San Joaquin, Stanislaus
Basin Notes
2003: Bulletin 118 basin description
2014: CASGEM basin prioritization – high. Comments: Estimated that 70,000 af/year of overdraft occurs in northeastern San Joaquin County and about 35,000 af/year of overdraft occurs in the Stockton East Water District (B‐118) & (USBR 1996). Basin experiencing long term GW overdraft 160,000AF/yr (local GWMP). From B118: as a result of overdraft poor quality groundwater has been moving east along a 16‐mile front on the east side of the Delta and has continued to migrate eastward (USACE 2001). Large areas of nitrate contamination are located in the subbasin.
2016: Basin boundary modification approved with Cosumnes 5-022.16 subbasin
Revised basin boundaries description
2018: Basin priority – high. Declining groundwater level and salt intrusion comments:
- CRITICAL OVERDRAFT. Source: DWR 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) The plan also must address whether and how placing water to underground storage and subsequently withdrawing the water, under Permit 10477 will prevent additional overdraft in the Eastern San Joaquin and Cosumnes groundwater subbasins and include measures to avoid any such impacts. Source: North San Joaquin Water Conservation District Conjunctive Use Plan Water levels are declining and chloride concentrations are increasing in western San Joaquin County as a result of pumping in excess of recharge. Source: San Joaquin Chlorides – supplementary drilling Stockton East Water District, U.S. Geological Survey (USGS).
- 1) In the Eastern San Joaquin subbasin, the groundwater is characterized with low to high salinity levels and localized areas of high calcium or magnesium bicarbonate, salinity, nitrates, pesticides, and organic constituents (DWR 2006j, 2013b). The high groundwater salinity is attributed to poor-quality groundwater intrusion from the Delta caused by the pumping-induced decline in groundwater levels, especially in the groundwater underlying the Stockton area since the 1970s (San Joaquin County Flood Control and Water Conservation District 2008). (pg. 7-34) The east side of the San Joaquin River is underlain by seven groundwater subbasins: the Cosumnes, Eastern San Joaquin, Modesto, Turlock, Merced, Chowchilla, and Madera subbasins. Declining groundwater levels in the subbasins east of the San Joaquin River have resulted in an area approximately 16-miles long with high salinity due to saltwater intrusion from the Delta (USFWS 2012). Doesn’t say along which 16-mile stretch of which sub-basin (Cosmunes, East San Joaquin, Modesto, Turlock, Merced, Chochilla, Madera). (pgs. 7-32, 7-33) Source: Coordinated Long Term Operation of the Central Valley Project, EIS, US Bureau of Reclamation, Chapter Seven. 2) In the Eastern San Joaquin Groundwater Subbasin, near Stockton, California, 130 km east of San Francisco (Fig. 1), pumping in excess of recharge and resulting declines in water levels within aquifers to below sea level has led to an increase in chloride concentrations in water from wells (Izbicki et al. 2006). This trend began in the 1950s and has led to exceedances of the US EPA secondary maximum contaminant level (SMCL) of 250 mg/L for chloride in several wells (DWR 1967). In an effort to mitigate the impact of high-chloride water on groundwater supplies, local agencies, led by the Eastern San Joaquin County Groundwater Basin Authority in cooperation with the DWR, Stockton East Water District, and the City of Stockton, implemented strategies involving the conjunctive use of surface water and groundwater to meet demand. Artificial recharge programs have also been implemented that promote infiltration of captured local runoff to manage declining water levels and chloride concentrations. Programs include Stockton East Water District’s Farmington Groundwater Recharge Program, with a goal of recharging about 43,106 m3 /year annually through field-flooding (Stockton East Water District 2014) and the City of Stockton’s Morada Recharge Facility, which utilizes an existing stormflow basin to infiltrate local surface water and stormflow runoff (OLeary et al. 2012). Source: Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California, USA, Hydrogeology, 2015
2019: Basin boundary modification. Per DWR: “This basin boundary modification revises the Eastern San Joaquin and Tracy subbasin boundaries to align with the City of Lathrop’s city limits. The modification places the City of Lathrop entirely within the Tracy subbasin.” November – Groundwater Sustainability Plan published
2020: January 29 – GSP submitted to DWR.
2022: January 28 – DWR deems the GSP “incomplete,” stating it “has not defined sustainable management criteria (SMC) for the chronic lowering of groundwater levels” and “does not provide enough information to support the use of the chronic lowering of groundwater level SMCs and representative monitoring network as a proxy for land subsidence.”
July 27 – GSA re-submits revised GSP
2023: July 6 – Revised GSP approved by DWR
At-A-Glance
California Water Library Documents About This Basin
Assessing Causes and Consequences of Winter Surface Water Dynamics in California's Central Valley Using Satellite Remote Sensing
Wiley Online Library | June 3rd, 2025
California's Central Valley is increasingly vulnerable to winter floods. A comprehensive spatial baseline of flood extents is critical for inundation analyses that can en
CV-SALTS Preliminary Management Zone Proposal for Priority 2 Management Zones
Valley Water Collaborative | December 30th, 2024
The Nitrate Control Program is designed to achieve the following three management goals in the Central Valley Region: Goal 1 – Ensure a safe drinking water
Replenishing Groundwater in the San Joaquin Valley: 2024 Update
Public Policy Institute of California (PPIC) | June 6th, 2024
Strategies to replenish groundwater basins—long used in some areas of the San Joaquin Valley—have increasingly come into focus as the region seeks to bring its overd
Groundwater sustainability and land subsidence in California’s Central Valley
Water (MDPI) | April 22nd, 2024
The Central Valley of California is one of the most prolific agricultural regions in the world. Agriculture is reliant on the conjunctive use of surface-water and groundw
Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley
Nature Portfolio (Springer Nature) | September 8th, 2023
Statement of Findings regarding the Approval of the San Joaquin Valley - Eastern San Joaquin Subbasin Groundwater Sustainability Plan
California Department of Water Resources (DWR) | July 6th, 2023
Comparing Domestic and Public-Supply Groundwater Quality in the Northern San Joaquin Valley, 2019: California GAMA Priority Basin Project
U.S. Geological Survey (USGS) | June 5th, 2023
Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and publi
Comparing domestic and public-supply groundwater quality in the northern San Joaquin Valley, 2019—California GAMA Priority Basin Project
U.S. Geological Survey (USGS) | June 5th, 2023
Groundwater quality in the Northern San Joaquin Valley region of California was studied as part of California State Water Resources Control Board (SWRCB) Groundwater Ambi
LandFlex Program’s Guidelines
California Department of Water Resources (DWR) | December 8th, 2022
LandFlex is a program that will provide $25 million in block grants to local government agencies to grant to farmers who limit agricultural water use. Local government ag
Modeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California
Journal of Hydrology (Elsevier) | December 5th, 2022
The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contami
Subsurface water flux in California's Central Valley and its source watershed from space geodesy
American Geophysical Union (AGU) | September 29th, 2022
We combine measurements from Global Positioning System positioning and Gravity Recovery and Climate Experiment gravity to infer change in water components in Central Vall
Eastern San Joaquin Groundwater Subbasin Groundwater Sustainability Plan (Revised)
Eastern San Joaquin Groundwater Authority (ESJGA) | June 15th, 2022
In 2014, the California legislature enacted the Sustainable Groundwater Management Act (SGMA) in response to continued overdraft of California’s groundwater resources.
Statement of Findings regarding the Determination of Incomplete Status of the San Joaquin Valley – Eastern San Joaquin Subbasin Groundwater Sustainability Plan
California Department of Water Resources (DWR) | January 28th, 2022
The Department of Water Resources (Department) is required to evaluate whether a submitted groundwater sustainability plan (GSP or Plan) conforms to specific requirements
Incomplete Determination of the 2020 Eastern San Joaquin Subbasin Groundwater Sustainability Plan
California Department of Water Resources (DWR) | January 28th, 2022
The Department of Water Resources (Department) has evaluated the groundwater sustainability plan (GSP) submitted for the Eastern San Joaquin Subbasin (Subbasin) and has d
Post-Drought Groundwater Storage Recovery in California's Central Valley
American Geophysical Union (AGU) | October 5th, 2021
California's Central Valley has experienced chronic groundwater depletion over the past few decades, the rate of which was amplified by droughts in 2007–2009 and 2012?
Groundwater and Urban Growth in the San Joaquin Valley
Public Policy Institute of California (PPIC) | September 20th, 2021
The San Joaquin Valley is ground zero for the Sustainable Groundwater Management Act (SGMA). It has the largest groundwater deficit in California and faces some of the
Critical Aquifer Overdraft Accelerates Degradation of Groundwater Quality in California's Central Valley During Drought
American Geophysical Union (AGU) | September 1st, 2021
It has been established that wells are at risk to run dry when groundwater levels decline during drought, but associated impacts to water quality are poorly understood.
Quality of Groundwater Used for Domestic Supply in the Northern San Joaquin Valley, California
U.S. Geological Survey (USGS) | July 28th, 2021
Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Moni
Geologic Influences on the Quality of Groundwater Used for Domestic Supply in the Northern Sierra Nevada Foothills
U.S. Geological Survey (USGS) | May 25th, 2021
Approximately 2 million California residents depend on groundwater from domestic wells for their drinking-water supply. The State of California, in collaboration with the
Multiscale Assessment of Agricultural Consumptive Water Use in California's Central Valley
American Geophysical Union (AGU) | May 4th, 2021