Public Works
Department of Water Resources ApprovesTracy Subbasin Groundwater Sustainability Plan
February 9, 2024

(STOCKTON) The San Joaquin County Public Works Department announced today that the California Department of Water Resources (DWR) approved the Groundwater Sustainability Plan (GSP) for the Tracy Subbasin. This approval is a significant step toward ensuring state mandated regional groundwater sustainability by the year 2040 per the Sustainable Groundwater Management Act (SGMA). The GSP includes measurable objectives and milestones in five-year increments to achieve long-term groundwater sustainability.

SGMA was enacted in 2014 and is the first-ever comprehensive groundwater management legislation in California. SGMA requires Groundwater Sustainability Agencies (GSA) to develop GSPs that result in sustainable groundwater use within 20 years for groundwater basins designated by the state as medium- or high-priority. Successful implementation of SGMA would protect water quality and supplies for agricultural, municipal, environmental, and other beneficial uses.

The Tracy Subbasin GSAs consist of San Joaquin County, Banta-Carbona Irrigation District, Byron-Bethany Irrigation District, the cities of Lathrop and Tracy, and the Stewart Tract Reclamation District. Their plan outlines the GSAs' sustainability goals, how water levels and water quality will be measured, and what data should be collected regularly to confirm that GSP goals are being achieved.

The Tracy Subbasin consists of the roughly one-third of San Joaquin County that is southwest of the San Joaquin River and includes the cities of Lathrop and Tracy and the emerging community of Mountain House. Land use within the subbasin is approximately 60% agricultural, 7% urban, less than 1% managed wetlands, and 32% unclassified. Groundwater use in the Subbasin is low, about three percent of the total water use. There are about 2,400 wells in the subbasin, of which about 450 are agricultural and municipal, and about 1,950 are domestic wells. Users of groundwater in the Subbasin include agricultural, domestic and municipal/industrial well owners that include residents, Native American Tribes, local governments, irrigation districts, and the federal government.

The subbasin is designated by DWR as a medium priority, so Tracy Subbasin GSAs were required to submit their GSP by January 2022. rather than January 2020 when “critically over-drafted” subbasins throughout the state were required to submit plans. Under the SGMA statute, DWR had until the end of January 2024 to approve or comment on the GSP, and they approved it as submitted without comment. The GSAs must now implement the GSP, the cornerstone of which is to deliver, within 20 years, several projects that are expected to collectively reduce groundwater pumping by several thousand acre-feet per year.

“The good news is that the Tracy Subbasin is generally in good condition, so the efforts needed to achieve sustainable groundwater use are relatively modest,” said San Joaquin County Public Works Director, Fritz Buchman. “While there are minor groundwater quality issues that the plan seeks to address, the subbasin has experienced no chronic lowering of groundwater levels, no significant reduction in groundwater storage, no surface water depletion, no seawater intrusion, and no land subsidence due to groundwater extraction.”

“We are grateful to everyone who worked diligently and collaboratively to develop a GSP that will serve as a roadmap for achieving the Tracy Subbasin's sustainability goals well before the 2040 deadline,” said San Joaquin County Board of Supervisors Chair, Miguel Villapudua. “We especially appreciate DWR's thorough review of our GSP and their quick approval of the plan. Their actions support the Board of Supervisors' Strategic Priorities where we called for GSP approval by 2025. We are tremendously pleased that this goal was achieved 17 months ahead of schedule. We can now focus on implementing the plan and implementing groundwater projects that will best serve residents, farmers, and businesses who are users of our precious groundwater supply.”

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