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Groundwater description

 9/17/14 Update:

  • community meeting on the San Francisco Groundwater Program will take place on Sept. 23rd.
  • Groundwater is an essential part the state and the nation’s water supply. While San Francisco residents are not currently drinking groundwater, 80% of Californians depend upon groundwater for their drinking supply, and have been doing so safely for generations.
  • All water delivered by the Hetch Hetchy Regional Water System exceeds state and federal water quality requirements.
  • As California faces one 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.
  • The SFPUC has 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 Department of Public Health regulates drinking water supplies, and will monitor and issue a permit before any groundwater is blended into our drinking water supply.
  • Our Annual Water Quality Report is available for more information. 2013 data will be available in June.


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.

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

Groundwater Monitoring photoGroundwater is an important water supply source for other communities throughout the world. In California alone, it provides approximately 40 percent of the state’s drinking water. Our Groundwater Program currently includes two projects plus a Groundwater Stewardship and Management Program.

These projects will provide both local and regional benefits by increasing our water supply reliability, diversifying our water supply portfolio and reduce our dependence on a single source, thus making us less vulnerable to disrupted service from natural disasters such as earthquakes.

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Last updated: 9/17/2014 2:55:55 PM