Crystal Springs Reservoir Watershed
Map SatelliteThis large area embraces several ridges, creeks, artificial lakes, a portion of the San Andreas Rift Zone and other features.
Vegetation is primarily chaparral, with substantial areas of oak woodland, particularly on the northern slopes, some grasslands, mainly exotic, and, along the streams and occasionally on the lakesides, riparian .
Chaparral includes coyote brush, Baccharis pilularis, blue blossom, Ceanothus thyrsiflorus, yerba santa, Eriodictyon californicum, holly-leaved cherry, Prunus ilicifolia, among others.
In the oak woodland are found the coast live and the interior live oak, Quercus agrifolia and Quercus wislizenii, California buckeye, Aesculus californica, madrone, Arbutus menziesii, and California bay, Umbellularia californica. Among the latter, the largest in the State is reputed to be here (see Buri Buri Ridge).
At least eight species of rare plants occur in the watershed, with five in the vicinity of the Crystal Springs dam and canyon. The plants are Acanthomintha duttonii, Arabis blepharophylla, Arctostaphylos montaraensis, Cirsium fontinale var. fontinale, Eriophyllum latilobum, Erysimum franciscanum, Fritillaria liliacea, and Hesperolinon congestum. Pentachaeta bellidiflora, which has a restricted distribution, occurs here also.
The area is quite rich in wildlife, with over 160 species of birds, 17 of reptiles and 40-plus of mammals recorded. Some 70 of the bird species are waterfowl or shorebirds. The endangered San Francisco garter snake, Thamnophis sirtalis tetrataenia, is found in the area.
Geologically, the area presents a beautiful example of a rift valley. This feature is nearly a straight linear trough. Both San Andreas and Crystal Springs lakes were formed in the depression resulting from movement along the fault. (Dams have since augmented the size of what were once relatively small lakes or ponds.) While the valley was formed partly by the earth movements along the San Andreas Fault, more important has been the easy erosion of the badly crushed rock in the fracture zone. The lake gave its name to the fault.
Rocks in the area include those of the Franciscan formation, some Plio-Pleistocene nonmarine sedimentaries, some Eocene marine sandstones and shales and, eastward of the fault, serpentine.
See also Lower Crystal Springs Rift Monuments and Woodside Sag Pond.
Integrity: There are trails and roads in the area, including a freeway. The rare plants on the freeway-cut area have been fenced. There are several dams in addition to those mentioned above. However, most of the area is relatively undisturbed. No major fires have occurred in the area in the past 50 years.
Use: Research, educational, observational. Use is restricted, however.
September 1976
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman
