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
At-A-Glance
Located in California’s San Joaquin River hydrologic region, the San Joaquin Valley – Merced is 512,959 acres in size. This High priority basin is home to an estimated 174,527 people (2010 value), which have been at a rate of 38.11.
San Joaquin Valley – Merced is a(n) basin with approximately 6126 wells, of which approximately 141 are water supply wells. Groundwater accounts for approximately 66.81 percent of the basin’s water supply.

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 Turner Island Water District Groundwater Sustainability Agency (TIWD GSA)
2020: January 28 – GSP submitted to DWR