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San Francisco Groundwater Supply Project

Strengthening San Francisco's Water Supply

SFPUC: Groundwater Educational Video from BAYCAT on Vimeo.

On an average day, the City of San Francisco – its residents, businesses, and visitors – consumes about 63 million gallons of water. This water is supplied by the Hetch Hetchy and Bay Area reservoirs. Developing local groundwater helps diversify our supply portfolio and ensure we have a local source for water should a drought, earthquake or other disaster interrupt our Regional Water System supply. A project overview can be found here.

A Reliable Local Source of Water

On an average day the City of San Francisco – including our residents, businesses and visitors – will continue to rely primarily on the SFPUC Regional Water System, a system that combines the resources of the Hetch Hetchy Reservoir with 5 reservoirs in the Bay Area, for 60 million gallons of drinking water. Adding groundwater to our regional water supplies makes San Francisco’s water supply more reliable, particularly in the event of droughts and emergencies.

Water Quality: Our Highest Commitment

For the past decade, we have collected water quality data from the Westside Basin aquifer. With this extensive testing and data collection, we know that our local groundwater is a high-quality source of water. After blending our local groundwater with our other supplies, we will continue to provide drinking water that surpasses all State and Federal drinking water standards.

As part of the Project, we developed a comprehensive water quality monitoring program that samples and analyzes both the water from individual production wells and the blended water supplied to customers. To keep our customers informed about their water supply during the start-up phase of project implementation, we update the results of water quality monitoring of the blended water supply twice a month (at the end of the first and third week of each month). The Latest Groundwater Blend Report is at the bottom of this page.

How it Works

In April, 2017,we began pumping groundwater from the Westside Groundwater Basin aquifer that extends from approximately 300-600 feet below ground. The groundwater is treated and blended with our regional drinking water supplies before it is delivered to our customers. Over the next few years we will continue adding groundwater in order to reach our goal of blending 4 million gallons a day (mgd) of treated groundwater with our regional water supplies. 

Golden Gate Park central groundwater well site
West Sunset groundwater well station site
SFGW SSunset
South Sunset groundwater well station site
Lake Merced groundwater well station site

As of July 2020 all six well stations have been completed. The groundwater is treated with chlorine and then delivered to the Sunset and Sutro reservoirs. The blended water is served to more than half of the our customers in the City. San Francisco’s drinking water supplies are tested daily with a network of instrumentation throughout our regional water system as well as through manual sampling.

SFGW Irrigation

One of two irrigation wells that have been converted for drinking water.

thumnail image of the distribution map


More than Just a Well!

The design of the North Lake and West Sunset well stations includes features that will allow it to serve as an emergency drinking water supply. It can be connected to a generator for backup power, provide on-site disinfection, and be connected to a dedicated hydrant for filling water tanker trucks.

A Vital Project with Multiple Benefits
The San Francisco Groundwater Supply Project is an important component of the Water System Improvement Program and provides both local and regional benefits.
  • Local: Our environment and our City face many unknowns in the future from possible drought, earthquakes and climate change. A local water source will give us more control over the use and operation of our water supplies.
  • Sustainable: Groundwater is a renewable water source that is replenished through natural processes.
  • Reliable: This project diversifies the City’s water supply portfolio, which will reduce our dependence on a single source, thus making us less vulnerable to disrupted services.
  • Responsible: This project will coordinate closely with the SFPUC’s Westside Basin Groundwater Monitoring Program, a robust monitoring network, to make sure that we operate in a responsible and sustainable manner so that this groundwater resource basin will be available for generations to come. 
Project Information
August 2014
Fall 2019
Cost $66 Million
Planning and Reporting Documents

The information shown reflects the current forecast information published in the latest WSIP Quarterly Report.



Last updated: 12/4/2020 2:05:03 PM