The lake is on
Arroyo Valle (Spanish for "creek of the valley") in the
Diablo Range, and is formed by Del Valle Dam, completed in . The lake and dam are part of the
California State Water Project, as part of the
South Bay Aqueduct. The lake serves in part as off-stream storage for the South Bay Aqueduct. The capacity of the lake is , however, the lake has a flood storage of . Thus normally stores . The lake is a popular destination for hikers, bikers, and boaters. The
Hetch Hetchy Aqueduct passes below the lake, but does not connect to it. The
California Office of Environmental Health Hazard Assessment issued a fishing advisory regarding the mercury levels of fish caught from the body of water. ==Dam description==