Fact Brief: Is Anderson Dam the largest water reservoir in the county?

The Anderson Dam and Reservoir is the largest dam complex of Santa Clara County’s 10 reservoir and dam systems. Built in the 1950s, Anderson Dam holds a maximum of 90,373 acre-feet of water, or roughly equal to 29 billion gallons of water for residents. Second to Anderson Dam is Coyote Dam and Reservoir with 23,244 acre-feet of water. 

In 2011, a seismic evaluation found the downstream and upstream embankments could be at risk during a large earthquake. In 2020, the Federal Energy Regulatory Commission directed Valley Water to reduce Anderson Reservoir to “dead pool,” or as low as possible, until the seismic work was completed.

After that finding, Anderson Dam has been at 3% capacity while repairs are made. Retrofits to improve the dam’s earthquake resiliency and return the installation to its full capacity will begin in early 2027 and are expected to be finished by 2034.