San Andreas Lake

The reservoir San Andreas Lake finds its genesis in the San Andreas Fault of San Mateo County, California. The lake was originally classified as a sag pond when first discovered in 1769 by the Spanish Portola Expedition party. The area received its name from Portola’s chaplain and diarist, Father Francisco Palou, who named it San Andreas in honor of the saint’s feast day.

Rolling over a surface area of 550 acres, the lake only expanded when the Spring Valley Water Company constructed a dam in 1869- San Andreas Dam.  Since much of the water from this lake is diverted to agricultural and drinking water need, recreational water sports are prohibited, however, the lake area allows for hiking, bicycling, roller skating, and picnicking.

The company later enlarged San Andreas Lake by creating two additional lakes in the same valley- Upper and Lower Crystal Springs Reservoirs, which are responsible for holding the water supply for the City of San Francisco. The water first comes via Aqueduct from the Hetch-Hetchy reservoir in the Sierra Nevada Mountains, then in a tunnel under the Southern part of San Francisco bay up to the San Francisco peninsula, and finally enters the reservoirs at the “Water Temple”.