Alameda Creek Watershed Local Supplies

About the Watershed

The Alameda Creek watershed is an area of roughly 633 square miles, stretching from Mt. Diablo in the north to Mt. Hamilton in the south, and east to Altamont Pass. The area is populated by more than 200,000 people living in five cities—Dublin, parts of Danville and San Ramon, Livermore, Pleasanton—and thousands more living in unincorporated areas.

Most of the watershed is undeveloped, open range. Another large portion is comprised of public lands and parks. A smaller portion is used as cropland. Only about seven percent of the total acreage is used for residential, commercial, and industrial purposes.

The average rainfall in the Alameda Creek watershed is approximately 20 inches per year. Runoff from much of the southern region is collected in Calaveras and San Antonio Reservoirs, which are part of San Francisco's water system. Runoff from much of the southeast portion is collected in Del Valle Reservoir, some of which is diverted to ACWD via the South Bay Aqueduct. Runoff from the northern region flows to tributaries of Alameda Creek, where it is carried to ACWD facilities and used for groundwater recharge.

The Supply

Virtually all of our local water supply (which comprises 40% of our total distribution system supply) originates in the Alameda Creek watershed. Rainwater runoff from the watershed and a portion of our State Water Project supply is captured behind three large, inflatable rubber dams which span the width of the Alameda Creek Flood Control Channel. These dams divert water to several hundred acres of ponds (former gravel quarries) where water percolates to recharge the underlying Niles Cone Groundwater Basin.

Watershed Protection

Protecting the integrity of the watershed is of critical importance to ACWD. The District continuously samples, analyzes, and monitors the quality of water in Alameda Creek at a special monitoring facility located at the mouth of Niles Canyon near Mission Boulevard and at other key locations throughout the watershed. In addition, we work with property owners and other agencies to encourage proper use of watershed lands so that the water quality in the creek is protected and maintained.