Union Valley Reservoir, reservoir in Eldorado National Forest, El Dorado County, California, United States

Union Valley Reservoir is a 277,000 acre-foot lake in Eldorado National Forest in the Sierra Nevada, about 20 miles northeast of Placerville at 4,870 feet. It was formed in 1963 by the 453-foot earth and rockfill Union Valley Dam on Silver Creek. Forested hills, wooded peninsulas and small islands line its irregular shore; a low circular stone overlook wall with small plaques stands above the water.

Union Valley Reservoir was created in 1963 when the 453-foot earth-and-rockfill Union Valley Dam was built across Silver Creek, a tributary of the American River. The dam and reservoir belong to the Upper American River Project of the Sacramento Municipal Utility District, which stores spring snowmelt and releases it in summer to a chain of downstream hydroelectric plants. The Union Valley Powerhouse at the dam's base has a capacity of 46.7 MW and runs as a peaking plant. Consumptive water rights are held by the City of Sacramento.

The reservoir is part of the Upper American River Project of the Sacramento Municipal Utility District, a public electric utility that operates the dam and other dams in the area. Water is held by the City of Sacramento, which holds consumptive rights to it. Recreation such as boating, fishing and camping is available there.

The area operates from late spring through early fall with multiple campgrounds offering varied amenities, from basic tent sites to locations with picnic tables and grills. Access is via Ice House Road about 15 miles north of Highway 50, with free boat launches available at several campground locations.

The reservoir stores spring snowmelt and releases it in summer to a chain of hydroelectric plants downstream. Union Valley Powerhouse, at the base of the 453-foot earth and rockfill dam, has a capacity of 46.7 MW and runs as a peaking plant during highest demand. The City of Sacramento holds consumptive rights to the water.