Located in California’s San Francisco Bay hydrologic region, the Westside is 25,392 acres in size. This Very Low priority basin is home to an estimated 350,624 people (2010 value), which have been at a rate of 7.13.

Westside is a(n) basin with approximately 100 wells, of which approximately 17 are water supply wells. Groundwater accounts for approximately 9.55 percent of the basin’s water supply.

Source: CA DWR
Source: CA DWR

Basin Notes

2003: Bulletin 118 basin description

2005: The Westside Groundwater Basin and its Hydrostratigraphic Units, San Francisco and San Mateo Counties, California, Geological Society of America

2017: Annual Groundwater Monitoring Report, Westside Basin, San Francisco and San Mateo Counties, California, San Francisco Public Utilities Commission

2018: Draft basin prioritization salt intrusion comment

  • 1) Natural sources of TDS to groundwater in the San Francisco Bay study unit (Marina, Lobos, Downtown, Islais Valley, South San Francisco, Visitacion Valley, Westside, and the Santa Clara Valley groundwater basins ) include saltwater intrusion from the Bay and interaction between recharge water and aquifer materials derived from marine or estuarine sediments. On the east side of the Bay, high and moderate concentrations of TDS were detected in areas with a history of intrusion of water from the Bay in response to pumping of freshwater from aquifers. Source: USGS 2) The two areas monitored for seawater intrusion (the Pacific Coast and the Bay Coast) contain a number of monitoring wells completed in the various aquifers present in the Westside Basin. The two sets of wells are known as the coastal and Bay side monitoring networks. Groundwater head in the Westside Basin is monitored in a network of production and monitoring wells as part of the semi-annual monitoring program that was initiated throughout the Basin in 2000. (Doesn’t say if they’re operating the wells differently in response to seawater intrusion). Using surface water–remediated. – SFArea-SeaWaterIntrusionSFArea-Task 10.pdf

Bulletin 63: Seawater Intrusion in California, Department of Water Resources, 1958

2018 Final Basin Prioritization: Basin status remains unchanged at very low priority.

GSA Information