Union Valley Reservoir
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Union Valley Reservoir is a reservoir in eastern El Dorado County, California, about 20 miles northeast of Placerville. The 230,000 acre-foot reservoir is in El Dorado National Forest in the Sierra Nevada at an elevation of 4,870 feet. It is formed by Union Valley Dam on Silver Creek, which is a tributary of the American River. The 453-foot earth and rockfill dam was completed in 1963. The reservoir is owned by the Sacramento Municipal Utility District, a public electric utility, which operates the dam and many other dams in the area. Recreation such as boating, fishing and camping is available there.
It stores snow melt runoff during the spring and releases it during the summer when electrical demand is greatest to a chain of hydroelectric power plants downstream. Union Valley Powerhouse at the base of the dam has a capacity of 46.7 MW and is operated as a peaking power plant, supplying electricity during times of the greatest demand. Rights to the water itself are held by the City of Sacramento, California.
Though it is said to be on Silver Creek, the reservoir is fed by Big Silver Creek, Jones Fork Silver Creek, Tells Creek, Wench Creek and the outflows of Robbs Peak and Jones Fork powerhouses. Jones Fork Powerhouse is not on Jones Fork Silver Creek. The water comes from Ice House Reservoir through a tunnel. Robbs Peak Powerhouse gets its water from Gerle Creek Reservoir and Loon Lake Reservoir, both on Gerle Creek, and Robbs Peak Reservoir on the South Fork of the American River. Downstream from Union Valley Dam, Silver Creek flows into Junction Reservoir and then Camino Reservoir before meeting the South Fork of the American River a few miles north of Pollock Pines, California. Before the dam was built, Silver Creek was an intermittent creek which often did not flow during late summer and autumn. Yet today, tunnels between the reservoirs divert nearly all of the creek's water for hydroelectricity production.
