Folsom Lake

Folsom Lake is a reservoir on the American River in the Sierra Nevada foothills of California, United States. It is located within Placer, El Dorado, and Sacramento counties. It is about 25 miles northeast of Sacramento. The lake surface area is 11,500 acres its elevation is 466 feet and it has 75 miles of undulated shoreline. Folsom Lake and the surrounding Folsom Lake State Recreation Area is one of the most visited parks in the California Park system.

The Folsom Lake reservoir is formed by Folsom Dam, built in 1955 to control and retain the American River. The dam and reservoir are part of the Folsom Project, which also includes the Nimbus afterbay reservoir and dam facilities. The Folsom Project, operated by the United States Bureau of Reclamation, is part of the Central Valley Project, a multipurpose project that provides flood control, hydroelectricity, drinking water, and water for irrigation.

When the dam was built, it was designed to hold 976,000 acre feet with a surface area of 11,450 acres. The dam is 1,400 feet wide and 340 feet high. It is a concrete structure with approximately 9 miles of earth fill wing dams and dikes supporting its surrounding areas.

Folsom Lake during the 2011–2017 California drought.

During the drought of late 2013, part of the 2012–14 North American drought, the town known as Mormon Island reappeared 58 years after being submerged under Folsom Lake, with stone walls from some of the outlying areas being revealed by the shrinking lake.

California buckeye, blue oak, valley oak, digger pines, black oaks and occasionally oracle oaks populate the area surrounding the lake. A variety of wildflowers thrive in the Spring, Indian paintbrush, California poppy, larkspur, lupine, bordicaea, fiddleneck, Dutchman's pipe and monkey flower can be seen throughout the SRA.

A number of mammals inhabit the lake area including, coyotes, gray foxes, rabbits, skunks, raccoon, ground squirrels, black-tailed deer, opossums, and on occasion mountain lions, bobcats, and black bears have been sighted.

A number of birds call Folsom Lake home year round, bushtits, quails, wrens, scrub jays, black birds and towhees. Near the water visitors often see kingfishers, red-tailed hawks, eagles, kestlers, gulls and other raptors looking for a meal.

For eight months of the year, October 1 through May 31, the dam and lake is utilized to prevent flooding on the lower end of the American River. The Sacramento basin is notorious for flooding and the dam helps relieve winter storm runoff and snow melt from the Sierra.

It is a major component of the American River Watershed. During the summer months, water is released to prevent salt water intrusion in the San Joaquin Delta. These releases maintain water quality and keep ideal water temperatures for anadromous fish species such as Chinook salmon, steelhead and American shad. Several of these species are of primary concern due to their decline in numbers and spawning habitat destruction.

Water in Lake Folsom is also utilized for drinking water and power generation throughout the year. As a reservoir, the water levels in the lake fluctuate between 440 feet in the early summer and 405 feet in the early winter. In drought years, the water levels can be drawn below 400 feet in elevation. Some of the factors that affect these levels include precipitation, downstream flows and fishery needs.