County of Los Angeles Department of Public Works

Santa Clara River Watershed

The Santa Clara River is the largest river system in southern California that remains in a relatively natural state. The river originates in the northern slopes of the San Gabriel Mountains in north Los Angeles County, traverses in a westerly direction into Ventura County, and discharges into the Pacific Ocean near the City of Ventura. The river runs approximately 100 miles from its headwaters near Acton, California, to its outlet, and drains an area of approximately 1,600 square miles.

For ease of reference, the portion of the river within Los Angeles County is generally referred to as Upper Santa Clara River, and the portion within Ventura County is generally referred to as Lower Santa Clara River. The Upper Santa Clara River watershed consists of approximately 680 square miles of mostly natural land with some mixed use developed areas. Much of the development concentrates in or near the City of Santa Clarita, the lone incorporated city in the Upper Santa Clara River watershed.

Some of the major tributaries in the Upper Santa Clara River watershed include Castaic Creek, San Francisquito Canyon, Bouquet Canyon, Sand Canyon, Mint Canyon, and Santa Clara River South Fork.