Imported water

The Santa Clara Valley Water District supplies water to local water retail agencies, which in turn provide it to their customers in Santa Clara County. In order to maintain maximum efficiency and flexibility, the water supply comes from a variety of sources. Nearly half is from local groundwater aquifers, but more than half is imported.

The district imports water in the Bay Area because there is not enough local supply to serve the growing population. The Bay Area is a semi-arid region; with a limited annual rainfall of 10 to 20 inches per year, often less. In comparison, the average precipitation (including snow) in the midwest is 100 to 200 inches per year.

California has the largest water transport system in the world. Most of the state, except the northernmost areas, import water.

Santa Clara County's imported water comes from the Sierra Nevada mountains via the Sacramento-San Joaquin River Delta. This water is delivered by both the State Water Project (SWP) and the federal Central Valley Project (CVP).

Imported water is conveyed to the county through three main pipelines: the South Bay Aqueduct, which carries water from the SWP, and the Santa Clara Conduit and Pacheco Conduit, which bring water from the CVP.

The San Francisco Water Department conveys water from the Hetch-Hetchy reservoir into Santa Clara County through its own facilities.