San Joaquin Valley – Tracy

Source: CA DWR

San Joaquin Valley – Tracy



Located in California’s San Joaquin River hydrologic region, the San Joaquin Valley – Tracy is 238,428.97 acres in size. This Medium priority basin is home to an estimated 113,882 people (2010 value), which have been at a rate of 61.

San Joaquin Valley – Tracy is a(n) basin with approximately 3905 wells, of which approximately 96 are water supply wells. Groundwater accounts for approximately 3.00 percent of the basin’s water supply.

Source: CA DWR
Source: CA DWR

Basin Notes

2003: Bulletin 118 basin description

2014: CASGEM basin prioritization – medium. Comment: Poor water quality throughout the subbasin (B‐118)

2016: Basin boundary modification requests – one to subdivide the Contra Costa portion of the Tracy subbasin that was denied, while a suite of changes to the boundaries with the Kings 5-022.08, Madera 5-022.06, Westside 5-022.09, Delta-Mendota 5-022.07 subbasins were  approved

2018: Draft basin priority – medium. Declining groundwater level and salt intrusion comments:

  • 1) CASGEM/WDL/GWIDS: Stable hydrographs. Source: DWR 2) Review of hydrographs from wells throughout the sub-basin indicates that, except for seasonal variation resulting from recharge and pumping, water levels in most of these wells have remained stable over at least the last 10 years. Source: City of Tracy, Tracy Hills Specific Plan SB610/SB221 Water Supply Assessment Final Report, West Yost Associates, 12/2014
  • 1) City of Antioch: In April 2003, a source water assessment was conducted for the Antioch Municipal Reservoir and the San Joaquin River source of the City of Antioch water system. The San Joaquin River source was found to be most vulnerable to the effects of saltwater intrusion, chemical/petroleum processing or storage, and regulated point discharges. Water from the San Joaquin River is not always acceptable due to saltwater intrusion. Historically, as major diversions began and the freshwater flows into the Delta decreased, saline bay waters have moved further upstream, replacing the fresh water. When chloride levels in the river exceed 250 milligrams per liter, the City stops pumping until chloride levels decrease. – City of Antioch Annual Water Quality Report 2) The Emergency Drought Barrier was installed from early May through mid-November in 2015. It was constructed in West False River to protect the interior of the Sacramento-San Joaquin Delta from saltwater intrusion during prolonged and exceptional drought conditions. – 2015 Emergency Drought Barrier Water Quality Monitoring Report, DWR, January 2017

2019: Basin boundary modification. Per DWR: It “subdivides the Tracy subbasin along the Contra Costa County line. Multiple outreach meetings were held throughout the basin, and letters were delivered to water systems and local agencies. The requesting agency obtained the required three-quarters support from local agencies and public water systems for a jurisdictional subdivision.” Phase 2 draft priority: medium.

GSA Information

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