The cities, water districts and private utilities represented by the Bay Area Water Supply and Conservation Agency (BAWSCA) rely upon the San Francisco Regional Water System system for water to protect the health, safety and economic well being of 1.8 million citizens, businesses and community organizations. Together, the BAWSCA agencies account for two-thirds of water consumption from the system and pay for two-thirds of its upkeep.
The regional water system provides water to San Francisco, Santa Clara, Alameda and San Mateo counties. Eighty-five percent of the water comes from Sierra Nevada snowmelt stored in the Hetch Hetchy reservoir situated on the Tuolumne River in Yosemite National Park. Hetch Hetchy water travels 160 miles via gravity from Yosemite to the San Francisco Bay Area. The remaining 15 percent of water comes from runoff in the Alameda and Peninsula watersheds. This local water is captured in reservoirs located in San Mateo and Alameda counties.