Folsom Lake American River California

Originating in the Sierra Nevada, the North and Middle Forks of the American River join just upstream of the city of Auburn (Figure 1). From the North and Middle Forks confluence, the river flows past Auburn before entering Folsom Lake. Flows are released from Folsom Dam into Lake Natoma, which serves primarily as a reregulating reservoir. From Nimbus Dam, water is released downstream into the lower American River. It then flows through the American River Parkway (Figure 2), located in the densely populated Sacramento metropolitan area, for a distance of 23 miles before reaching its confluence with the Sacramento River. The average annual runoff is about 2.7 million acre-feet. The annual flow regime of the river, however, has changed significantly since construction of Folsom and Nimbus Dams in 1955. Nimbus Salmon and Steelhead Hatchery is located just below Nimbus Dam (Figure 3). Built in the early 1950's to compensate impacts of the Folsom project, it is operated by the California Department of Fish and Game under contract with the Federal Government. The lower American River floodplain is about 4,800 acres in size with an additional 4,000 acres of undeveloped adjacent lands. Of the 8,800 acres, about 5,000 acres are administered by Sacramento County as the American River Parkway (Figure 2). The parkway supports over 5 million visitor-use days annually with an estimated nonmarket value of $96 million (California Department of Fish and Game 1986), making it a very valuable regional asset.

Flowing through Sacramento County, the American River has long been a dynamic neighbor to those living along its waters. As the American River flooded, its banks were leveed, and its course was corrected to allow for further settlement and industry. Sacramento, in a feat of civic engagement, raised its business district above the floodplain, echoing the earthen mounds the Nisenan people used to raise their homes. Massive dredgers tore the riverbed in search of California's famous mineral. Railroad tracks, and later roads, were built to accommodate for more and more people living along its banks. The American River pressed those banks, but the residents of the Sacramento Valley persisted and created a vibrant capital for one of the world's largest economies.