Lafayette Reservoir, water storage reservoir in Contra Costa County, California, USA

Lafayette Reservoir is an open-cut, human-made terminal water storage reservoir owned by the East Bay Municipal Utility District, on a 925-acre site in Contra Costa County, California. The dark blue water has an irregular, branching shoreline, with a straight light-colored dam or causeway crossing the left arm. Dense green trees cover the slopes above and around the water, bordering it on nearly all sides.

Construction of the earth-filled dam began in 1928, but the clay foundation shifted as the concrete apron was poured, moving 26 feet between September 17 and 21. Engineers cut the planned capacity to one-third and paused work for three years before completing the dam in 1933. EBMUD opened the reservoir to public recreation in 1966.

The 2.7-mile paved Lakeside Trail circles the water, while the 4.5-mile Rim Trail climbs through the surrounding hills on dirt. Private rowboats, canoes, kayaks and small sailboats are allowed only if carried atop a car; gasoline engines are banned. A fenced children's play area, restrooms and a disabled-access fishing dock with adjacent parking are provided.

The outlet tower at the lake's southwestern corner was left unchanged when the dam was redesigned, so it stands far taller than its use requires. Its top is reached only by climbing metal rungs set into the side, and the small observation booth is almost always empty, its old doors green with oxidation.