San Joaquin Valley – Merced
Statistics
- Basin Name
- San Joaquin Valley – Merced
- Basin Number
- 5-022.04
- SGMA Basin Priority
- High
- Critically Overdrafted
- Yes
- Hydrologic Region Name
- San Joaquin River
- Counties
- Merced
Basin Notes
2003: Bulletin 118 basin description
2014: CASGEM basin prioritization – high
2018: Draft basin prioritization – high. Comments on groundwater level decline and subsidence:
- CRITICAL OVERDRAFT. Source: DWR 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) The Merced Groundwater Basin is in a state of groundwater level decline with a cumulative decrease in storage of approximately 720,000 ac-ft from 1980 to 2007.
- Sources : 1) Current Land Subsidence in the San Joaquin Valley, USGS; 2) 2014 – Land Subsidence from Groundwater Use in California, California Water Foundation / James W. Borchers / Michael Carpenter, Luhdorff & Salmanini, April 2014; 3) Progress Report: Subsidence in the Central Valley, California, Jet Propulsion Laboratory, California Institute of Technology, NASA 2015-16; 4) San Joaquin River Restoration Program / US Bureau of Reclamation monitoring
2018: Final Basin Prioritization: Basin status remains unchanged at high priority.
2019: November 12 – GSP published under joint powers agreement by the Merced Irrigation-Urban Groundwater Sustainability Agency (MIUGSA), the Merced Subbasin Groundwater Sustainability Agency (MSGSA), and the Turner Island Water District Groundwater Sustainability Agency (TIWD GSA)
2020: January 28 – GSP submitted to DWR
2021: DWR writes Merced GSP Plan Manager warning the GSP is deficient and to expect a determination of incomplete
2022: January 28 – DWR writes outlining deficiencies, including “The GSP does not provide sufficient justification for identifying that undesirable results for chronic lowering of groundwater levels, subsidence, and depletion of interconnected surface waters can only occur in consecutive non-dry water year types,” “The GSP has not defined sustainable management criteria for chronic lowering of groundwater levels in the manner required by SGMA and the GSP Regulations,” and “The GSP has not defined sustainable management criteria for land subsidence in the manner required by SGMA and the GSP Regulations.” The GSA is given until July 27 to re-submit a revised version.
July 26 – GSA submits a revised GSP
2023: August 4 — GSP approved by DWR
2024: July 31 – US Fish and Wildlife Service releases the 15-year plan, the San Luis National Wildlife Refuge Complex Final Comprehensive Conservation Plan and Environmental Assessment
At-A-Glance
California Water Library Documents About This Basin
2024 Annual Multibenefit Land Repurposing Program Report
California Department of Conservation (CDoC) | May 29th, 2025
The Multibenefit Land Repurposing Program (MLRP) increases regional capacity for repurposing irrigated agricultural land to uses that reduce reliance on groundwater while
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
Quantification of record-breaking subsidence in California’s San Joaquin Valley
Nature Portfolio (Springer Nature) | November 19th, 2024
San Luis National Wildlife Refuge Complex Final Comprehensive Conservation Plan and Environmental Assessment
U.S. Fish and Wildlife Service (FWS) | July 31st, 2024
This Comprehensive Conservation Plan (CCP) will guide the management of the Merced National Wildlife Refuge (NWR), San Luis NWR and Grasslands Wildlife Management Area (W
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
Multibenefit Land Repurposing Program Annual Report 2023
California Department of Conservation (CDoC) | April 9th, 2024
The Multibenefit Land Repurposing Program (MLRP) increases regional capacity for repurposing irrigated agricultural land to uses that reduce reliance on groundwat
Approved Determination of the Revised Groundwater Sustainability Plan Submitted for the San Joaquin Valley – Merced Subbasin
California Department of Water Resources (DWR) | August 4th, 2023
Quality of Groundwater Used for Domestic Supply in the Modesto, Turlock, and Merced Subbasins of the San Joaquin Valley, California
U.S. Geological Survey (USGS) | January 6th, 2023
More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domes
A simmering revolt against groundwater cutbacks in California
Stanford University | December 14th, 2022
In 2014, California legislators, focused on groundwater’s accelerating decline during a prolonged drought, passed the Sustainable Groundwater Management Act. Its impera
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
Merced Groundwater Subbasin Groundwater Sustainability Plan (Revised)
Merced Subbasin Groundwater Sustainability Agency (MSGSA) | July 6th, 2022
Due to size, this file has been divided into six part. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6
Statement of Findings regarding the Determination of Incomplete Status of the San Joaquin Valley - Merced 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
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?
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.
Groundwater development leads to decreasing arsenic concentrations in the San Joaquin Valley, California
Science of the Total Environment (Elsevier) | January 18th, 2021
In the San Joaquin Valley (SJV), California, about 10% of drinking water wells since 2010 had arsenic concentrations above the U.S. maximum contaminant level of 10μg/L.
Base of fresh water, groundwater salinity, and well distribution across California
National Academy of Sciences (NAS) | December 9th, 2020
The depth at which groundwaters transition from fresh to more saline—the “base of fresh water”—is frequently used to determine the stringency and types of measure
Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers
Nature Portfolio (Springer Nature) | July 24th, 2020
Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater stora
Groundwater Management and Safe Drinking Water in the San Joaquin Valley
Water Foundation | June 2nd, 2020
Domestic well vulnerability to drought duration and unsustainable groundwater management in California's Central Valley
Environmental Research Letters (IOP) | March 18th, 2020
Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and th