The American River is the second largest tributary to the Sacramento River, a critical component of the San Francisco Bay/Sacramento-San Joaquin Delta system. The Lower portion of the American River Watershed begins at Folsom Dam and flows about 30 miles to its confluence with the Sacramento River near downtown Sacramento. The watershed size is about 1875square miles with a watershed length of 30miles. The average annual precipitation is about 23inches.The Folsom Dam, which is within the watershed creates Folsom Lake, which provides flood protection for the Sacramento area; water supplies for irrigation, domestic, municipal, and industrial uses; hydropower; recreational opportunities; and maintenance of flows stipulated to protect fish and
