Crystal Springs Reservoir

Crystal Springs Reservoir is an artificial water body located in the northern Santa Cruz Mountains along the San Andreas Fault in San Mateo County, California. The reservoir consists of two large connected lakes that wind through a narrow forested valley between rolling hills covered with woodland and coastal scrub vegetation.

The Spring Valley Water Company built the lower dam in 1888, flooding the former resort community of Crystal Springs that once stood at this location. The upper dam followed in the 1930s, expanding the storage capacity and providing a larger supply of water for San Francisco.

The reservoir forms part of San Francisco's water infrastructure, supplying residents while preserving the surrounding natural environment for future generations.

A trail runs along the eastern shore and provides access to several viewpoints overlooking the water. The route is suitable for walking and cycling, while swimming and direct access to the water are not permitted.

The water comes partly from local rainfall and partly from Hetch Hetchy Reservoir in Yosemite National Park, connected by long-distance pipelines. The San Andreas Fault runs directly beneath the water through the middle of the reservoir.