San Joaquin Valley – Delta-Mendota
Statistics
- Basin Name
- San Joaquin Valley – Delta-Mendota
- Basin Number
- 5-022.07
- SGMA Basin Priority
- High
- Critically Overdrafted
- Yes
- Hydrologic Region Name
- San Joaquin River
- Counties
- Fresno, Madera, Merced, Stanislaus
At-A-Glance
Located in California’s San Joaquin River hydrologic region, the San Joaquin Valley – Delta-Mendota subbasin is 764,964.86 acres in size. This High priority basin is home to an estimated 117,012 people (2010 value). It has approximately 4206 wells, of which approximately 112 are water supply wells. Groundwater accounts for approximately 53 percent of the basin’s water supply.
Basin Notes
2003: Bulletin 118 basin description
2014: CASGEM basin prioritization – high
2016: Boundary modification approved a boundary change with Madera subbasin 5-022.06
Revised basin boundary description
2018: Draft basin priority – high. Groundwater level and subsidence comments:
- CRITICAL OVERDRAFT. Source: DWR 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) The change in groundwater levels in the northern part of the subbasin (Tracy to Westley) appears to show a consistent decline in groundwater levels. This decline could be indicative of a developing overdraft condition in that area. The change in groundwater levels in the southern part of the subbasin (West of Newman) also appears to show a consistent decline in groundwater levels. This decline could also be indicative of a developing overdraft condition in that area. Source: Groundwater Management Plan for the Northern Agencies in the Delta-Mendota Canal Service Area, Groundwater Management Plan Update, San Luis & Delta-Mendota Water Authority, July 2011
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
2019: Basin boundary modification. Per DWR: It “revised a portion of the shared boundary between the Chowchilla and Delta-Mendota subbasins to align with the jurisdictional boundaries of Triangle T Water District and Clayton Water District.” Phase 2 draft priority: high.
2020: January – Multiple GSPs submitted to the Department of Water Resources.
- San Luis & Delta Water Authority
- Farmers Water District
- Aliso Water District
- Grassland GSA/Merced County
- San Joaquin River Exchange Contractors GSP Group
- Fresno County Management Areas A and B
2022: January 21 – DWR determines combined GSPs are incomplete
July 20 – revised Farmers GSP submitted to DWR
July 20 – revised San Luis and Delta Water Authority GSP submitted to DWR
July 20 – revised Grasslands GSP submitted to DWR
July 20 – revised Aliso Water District revised GSP submitted to DWR
2023: March 2 – DWR finds revised GSPs inadequate