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Groundwater description

As surface water, such as rain, seeps into the ground, it passes between soil particles and collects in underground reservoirs called aquifers. An aquifer is made up of sand, silt, or other permeable materials that can readily yield water to springs or wells.

Groundwater is an essential part of the state and nationwide water supply. While San Francisco residents are not currently drinking groundwater, 80% of Californians depend on it for all or part of their drinking water supply, and have been doing so safely for generations.

Our Groundwater Program includes two projects, currently in progress, plus a stewardship and management program:

Together, these projects will increase our local and regional water supply reliability, diversify our water supply portfolio and reduce our dependence on a single source, making us less vulnerable to disrupted service from drought and natural disasters such as earthquakes.

Our future groundwater supply will come from the 45-square-mile Westside Basin, a series of aquifers extending from Golden Gate Park in San Francisco southward through San Bruno. The basin is a vital local resource for San Francisco and neighboring communities in San Mateo County.


San Francisco Groundwater Supply Project Update: January 2015

  • On November 18, 2014, the SFPUC Citizens Advisory Committee adopted a resolution in support of our San Francisco Groundwater Supply Project. The resolution followed a staff presentation the month before on our project and our commitment to water supply diversification.
  • Also in November, the S.F. Chronicle’s food and wine critics gathered for a blind tasting of our proposed San Francisco groundwater blend, our current San Francisco tap water blend, and commercially bottled water. The subsequent November 24 front page article reported on the tasting results, with preferences split between the current drinking water and the groundwater blend. The piece also noted the wine critic’s preference for the groundwater blend. 
  • As California faces some of the driest years on record, diversifying our water supply will allow us to stretch our essential drinking water in times of drought or during emergencies.
  • We have been studying and monitoring the quality of our groundwater basin for more than a decade as we prepare to bring this reliable local source back into our supply.
  • Once our groundwater is blended with our regional water supply, our drinking water will continue to be some of the highest quality water in the nation.
  • The State Water Resources Control Board, Division of Drinking Water Programs, regulates drinking water supplies, and will monitor and issue a permit before groundwater is blended into our drinking water supply.
  • Our Annual Water Quality Report is available for more information. 2014 data will be available in June.

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Last updated: 6/18/2015 3:06:22 PM