Crystal Springs Reservoir

Crystal Springs Reservoir is a key component of the San Francisco regional water system, located on the San Francisco Peninsula in San Mateo County, California. It is situated within the Santa Cruz Mountains and forms a significant part of the San Francisco Public Utilities Commission's Hetch Hetchy water supply network. The reservoir is renowned for its scenic beauty along the Interstate 280 corridor and its role in providing a protected habitat for local wildlife.

History

The valley was originally inhabited by the Ohlone people before European settlement. In the 19th century, the land was part of the Rancho de las Pulgas and later the Spring Valley Water Company, which constructed the original Lower Crystal Springs Dam in 1877 to create a reliable water source for the growing city of San Francisco. Following the 1906 San Francisco earthquake, the dam survived undamaged, proving its resilience. The entire system was purchased by the city in 1930, and the larger Upper Crystal Springs Dam was completed in 1888, with subsequent seismic upgrades. The area's history is also marked by the former route of the Southern Pacific Railroad and the submerged town of Nashville, which lies beneath the waters.

Geography and hydrology

The reservoir is actually a pair of interconnected basins—Upper and Lower—aligned along the San Andreas Fault rift zone within the Crystal Springs Valley. It is fed primarily by local watersheds including San Mateo Creek and Pilarcitos Creek, as well as imported water from the Hetch Hetchy Aqueduct. The surrounding terrain consists of steep, wooded slopes of the Santa Cruz Mountains, and the water body is bordered by Interstate 280 to the east and Sawyer Camp Trail to the west. The geology is dominated by Franciscan Complex bedrock and alluvial deposits, with the fault line influencing the linear shape of the valley.

Water supply and infrastructure

It serves as a major storage and distribution point for the San Francisco Public Utilities Commission (SFPUC), holding water delivered via the Hetch Hetchy Aqueduct from the Sierra Nevada. The reservoir's water is treated at the nearby Harry Tracy Water Treatment Plant before distribution to portions of San Mateo County, San Francisco, and other communities in the Bay Area. Key infrastructure includes the Upper Crystal Springs Dam (a concrete arch dam) and the Lower Crystal Springs Dam (an earthfill structure), along with connecting pipelines, valves, and pumping stations that integrate with the Regional Water System. Its strategic location provides critical emergency storage and pressure regulation for the peninsula.

Ecology and environment

The reservoir and its surrounding watershed are part of the protected San Francisco Peninsula Watershed, managed to preserve water quality and biodiversity. The area provides crucial habitat for species such as the California red-legged frog, San Francisco garter snake, and migratory birds like the American white pelican. Land use is strictly controlled to prevent contamination, with extensive fencing and patrols by the San Francisco Public Utilities Commission. The riparian corridors and coastal scrub plant communities are carefully managed, and the reservoir itself is closed to public contact to maintain its status as a primary drinking water source, minimizing pollution and algal bloom risks.

Recreation and access

While the reservoir's waters are closed to swimming, boating, and fishing to protect water quality, the surrounding lands offer significant recreational opportunities. The popular multi-use Sawyer Camp Trail and the San Andreas Trail run along its western and eastern shores, respectively, providing hiking, jogging, and cycling routes with views of the water and the Santa Cruz Mountains. These trails are part of the larger Bay Area Ridge Trail system. Access is managed by the San Mateo County Parks Department in cooperation with the San Francisco Public Utilities Commission, with parking available at designated trailheads off Highway 280 and Skyline Boulevard. The Crystal Springs Regional Trail complex connects to other open spaces like Edgewood Park and Natural Preserve.