San Mateo Creek (San Francisco Bay Area) - Ecology

Ecology

San Mateo Creek once hosted Coho salmon (Oncorhynchus kisutch) as evidenced by specimens collected by Professor Alexander Agassiz of Harvard University in the 1850s and 1860s. He also collected Steelhead trout (Oncorhynchus mykiss) from the creek. Historical records indicate that Chinook salmon (Oncorhynchus tshawytscha) occurred in at least two San Francisco Bay Area watersheds, San Mateo Creek in San Mateo County and San Leandro Creek in Alameda County.

Fog drip may play a key role in the precipitation in the upper watershed. On Cahill Ridge (just west of San Mateo Creek and east of Pilarcitos Creek, at an altitude of 1,000 feet, Oberlander measured fog drip beneath Tanoak (Lithocarpus densiflorus), Coast redwood and three Douglas fir trees, the latter 125 feet tall. He found that the trees most exposed produced the most precipitation and in five weeks of measurement (July 20-August 28, 1951) fog drip below the tanoak produced 59 inches of precipitation, more than the total annual precipitation on nearby grasslands and chaparral. The Douglas fir produced 7-17 inches of fog drip and appeared to provide unique conditions supporting the orchids Giant helleborine (Epipactis gigantea) and Phantom orchid (Cephalanthera austiniae), since these plants were found exclusively in these moist ridge tops.

The upper reach of the lower watershed of San Mateo Creek below Crystal Springs Dam consists of open space and sparsely developed residential areas of the cities of Hillsborough and San Mateo, California. This upper reach consists of closed canopy California oak woodland and serpentine grassland. The creek roughly parallels Crystal Springs Road through this section. Due to the unusual microclimate and presence of abundant serpentine there are an unusual number of rare plants in the upper catchment basin.

The middle reach consists of increasingly dense single family and multifamily residential land use along with some adjacent school, park and commercial uses. In the lower phase of the middle reach, San Mateo Creek is fully culverted through downtown San Mateo. In the lowest reach San Mateo Creek becomes tidal and discharges to San Francisco Bay between Ryder Park and Seal Point Park.

The creek mouth area contains slough and wetland habitats including mudflats that are known habitat of the endangered California Clapper Rail. San Mateo Creek was federally designated in 2002 as a section 303 impaired watershed for the substance diazinon; however, diazinon has been banned for golf course use by the U.S. Government. There is one golf course that provides surface runoff to San Mateo Creek in the city of San Mateo, and Crystal Springs Golf Course that drains to the Crystal Springs Reservoir.