Pacheco Reservoir


Pacheco Reservoir is an artificial lake or reservoir in the Diablo Range in California, U.S.A., formed by a dam on the north fork of Pacheco Creek. Located north of State Route 152 in eastern Santa Clara County, the lake is about an hour's drive from downtown San Jose.
The lake is formed by a dam across the north fork of Pacheco Creek, whose waters reach Monterey Bay by way of the Pajaro River.

North Fork Dam

The lake's waters are impounded by the North Fork Dam, an earthen dam built in 1939. The dam is high and long and contains of material. Its crest is above mean sea level.
The reservoir dam is an impassable barrier to in-migrating steelhead trout, preventing access to the nearly of stream consisting of North Fork Pacheco Creek, Mississippi Creek and East Fork Pacheco Creek. Resident rainbow trout successfully rear in fast-water habitats above the dam. They grow rapidly and reach smolt size by the end of their first summer. In many years in late spring, prior to reservoir releases for agriculture, low stream flows and high water temperatures severely impact steelhead fry and small juveniles.

Pacheco Reservoir Expansion Project

In 2018, the Santa Clara Valley Water District, Pacheco Pass Water District, and San Benito County Water District were awarded $484.5 million from California’s Water Quality, Supply and Infrastructure Improvement Act of 2014 to expand Pacheco Reservoir from its current operational capacity of 5,500 Acre-foot to 140,000 acre-feet. The expansion project involves building an earthen dam made of rock and soil upstream of the existing dam, a pump station, a pipeline, and other related infrastructure. The total project cost is projected to be $969,000,000.
In addition to runoff from the North Fork Pacheco Creek watershed, the reservoir will store imported water pumped from the San Luis Reservoir, which is located to the east along Highway 152 and is part of the Central Valley Project San Felipe Division in Merced and Santa Clara counties. The imported water would be supplied by the United States Bureau of Reclamation under contract to Valley Water and the San Benito County Water District.
In a drought or other emergency, the increased storage capacity will supply up to 1.4 million residents with water for a year. Water flow from the reservoir into Pacheco Creek will be managed to keep the creek flowing and improve the quality of habitat for South Central California Coast steelhead trout. Eight wildlife refuges in Central California will also be supplied with water.
Valley Water is currently exploring the project design and evaluating environmental impacts under a cost-sharing agreement with the California Water Commission. The draft environmental impact report is expected by 2022, with construction expected to begin in 2024.