Kern County Subbasin Staff Review of 2025 Draft of Groundwater Sustainability Plans

The Kern County Subbasin (subbasin or basin) is a critically overdrafted subbasin in the southern portion of the San Joaquin Valley with an area of about 1.78 million acres. The subbasin is currently managed by 20 GSAs. DWR determined the subbasin’s 2022 GSPs were inadequate and referred the subbasin to the State Water Board in March 2023, which initiated the state intervention process.

The subbasin GSAs submitted their revised, adopted GSPs to the Board in December 2024, and Board staff determined that these updated GSPs did not resolve all the deficiencies identified by staff in the previous GSPs. On February 20, 2025, the State Water Board held a hearing to determine whether to designate the subbasin as probationary.

In recognition of the substantial progress the subbasin made, the Board continued the hearing to September 17, 2025, giving the GSAs additional time to resolve the remaining deficiencies and directing the GSAs to submit revised draft GSPs to the Board by June 20, 2025 for review. On June 20, 2025, the GSAs submitted seven amended draft GSPs to the Board (2025 Draft GSPs). Board staff reviewed the 2025 Draft GSPs and conclude that the GSAs substantially, though not completely, address the deficiencies identified in the previous GSPs. Staff recommends returning the subbasin to DWR for review of the updated GSPs pursuant to Water Code section 10733.4 if the GSAs resolve three of the remaining issues: (1) providing an adequate mitigation program for drinking water wells impacted by any constituent for which a minimum threshold is established in the GSPs, including 1,2,3-TCP, where groundwater management activities cause concentrations to exceed those minimum thresholds; (2) providing an adequate mitigation program for state small water system wells (or domestic wells with more than four service connections) impacted by groundwater management activities; and (3) eliminating the Kern Non-Districted Land Authority GSA Joint Exercise of Powers Agreement May 2026 sunset provision, which would result in unmanaged areas of the subbasin that are a potential basis for state intervention.