San Mateo Creek (San Francisco Bay Area) - Watershed

Watershed

San Mateo Creek's source elevation is at almost 1,000 feet on Sweeney Ridge from which it flows southeasterly (in a valley east of Cahill Ridge and west of Sawyer Ridge) for 11.2 km (7 mi) before entering the northwest arm of Lower Crystal Springs Reservoir. The northeast arm of Lower Crystal Springs Reservoir is formed by San Mateo Creek's tributary, San Andreas Creek which descends to the Reservoir southeast along the San Andreas Rift. Another tributary, Laguna Creek, flows northwards from Woodside with its source on Edgewood County Park and Natural Preserve, and historically fed Laguna Grande and then joined San Mateo Creek just upstream from Crystal Springs Canyon, where San Mateo Creek turned east to flow through the canyon. Laguna Grande was submerged when an earthen dam (this was the first Crystal Springs Dam) was constructed in 1877, forming Upper Crystal Springs Reservoir. The old earthen dam became a causeway between Upper and Lower Crystal Springs Reservoirs when the latter was formed by Herman Schussler's concrete Crystal Springs Dam, which dammed up San Mateo Creek in 1888 to form the lower reservoir. The causeway is now crossed by Highway 92. In addition to San Mateo Creek and its San Andreas Creek and Laguna Creek tributaries, the waters of Crystal Springs Reservoir consist of runoff from the eastern slopes of the Montara block of the Santa Cruz Mountains and imported Hetch Hetchy Aqueduct water deriving from the Sierra Nevada. The two Crystal Springs lakes and San Andreas Lake used to be known as Spring Valley Lakes for the Spring Valley Water Company which owned them. Lower Crystal Springs Reservoir now covers the town of Crystal Springs which grew up around a resort of the same name.

From the Crystal Springs Dam San Mateo Creek flows generally northeast 8 km (5 mi) through San Mateo where it is partly intermittent and altered, to San Francisco Bay about 1.1 km (0.7 mi) west of the mouth of Seal Slough. This watercourse lies entirely within San Mateo County and flows generally eastward to discharge into San Francisco Bay.