Groundwater Basin Number: 5-22.07
County: Stanislaus, Merced, Madera, Fresno
Surface Area: 747,000 acres (1,170 square miles)
The Delta-Mendota Subbasin is bounded on the west by sediments of the Coast Ranges, and on the north by the Stanislaus/San Joaquin County line. The eastern boundary follows the San Joaquin River to Township 11S, where it jogs eastward and follows the eastern boundary of Columbia Canal Company to the San Joaquin River, then follows the Chowchilla Bypass and the eastern border of Farmer’s Water District. It then trends southerly through Township 14S Range 15E on the eastern side of Fresno Slough, then follows the Tranquillity Irrigation District boundary to its southern extremity. Heading northward, it follows the eastern, northern, and northwestern boundary of San Joaquin Valley – Westside Groundwater Subbasin (corresponding with Westlands Water District boundaries).
The Delta-Mendota Subbasin is designated a high priority basin by the California Department of Water Resource’s (DWR) CASGEM program.
Groundwater Management Plan
The San Luis & Delta-Mendota Water Authority developed a groundwater management plan (also known as a AB 3030 plan) for the northern agencies in the Delta-Mendota Canal Service Area in 1997. In 2011, the plan was updated to respond to new State legislation. Click here [link to pdf] for the 2011 Groundwater Management Plan.
GSAs in the Delta-Mendota Subbasin
As of June 2017, there are 24 Groundwater Sustainability Agencies (GSAs) in the Delta-Mendota Subbasin that have submitted formation notices with DWR:
Aliso Water District
Central Delta-Mendota Region Multi-Agency
City of Dos Palos
City of Firebaugh
City of Gustine
City of Los Banos
City of Mendota
City of Newman
City of Patterson
County of Madera—3
Farmers Water District
Fresno County—Management Area ‘A’
Fresno County—Management Area ‘B’
Grassland Water District
Ora Loma Water District
Patterson Irrigation District
San Joaquin River Exchange Contractors Water Authority
Turner Island Water District-2
West Stanislaus Irrigation District—1
West Stanislaus Irrigation District—2
Widren Water District
Sustainable Groundwater Management Act
- Establishes a definition of “sustainable groundwater management”
- Requires that a Groundwater Sustainability Plan (GSP) be adopted for high- and medium-priority groundwater basins in California
- Establishes a timetable for adoption of GSPs
- Empowers local agencies to manage basins sustainably
- Establishes basic requirements for GSPs
- Provides for a limited state role
The following dates are key milestones for GSAs:
June 30, 2017
All medium and high priority basins are required to establish GSAs or equivalent entities. The State Water Resources Control Board may hold a meeting to designate basin as “probationary” if a GSA or approved alternative is not established.
July 1, 2017
Counties must affirm or disaffirm responsibility as a GSA if no GSA has been established. The State Water Resources Control Board adopts a schedule for “state back-stop”-related costs.
December 15, 2017
The State Water Resources Control Board begins collecting annual reports from persons extracting more than 2 acre-feet per year (AFY) of groundwater from areas not managed by a GSA.
January 31, 2020
High and medium priority basins identified as critically overdrafted must be managed under a GSP. GSAs have 20 years from the date of adopting their GSP to achieve basin sustainability.
January 31, 2022
All other high and medium priority basins must be managed under a GSP. GSAs have 20 years from the date of adopting their GSP to achieve basin sustainability.