Lake Del Valle was created in 1968 by the construction of the Del Valle Dam, an earth-fill dam measuring 235 feet in height.
The reservoir provides essential water storage for the Alameda County Flood Control and Water Conservation District.
The park functions as a major staging area for the Ohlone Wilderness Trail, a 28-mile regional trail connecting several East Bay parks.
The water level in the lake fluctuates significantly throughout the year depending on State Water Project deliveries.
Lake Del Valle is stocked regularly by the Department of Fish and Wildlife with rainbow trout and occasionally catfish during the warmer months.
The park contains fossil beds that have revealed marine remains dating back to the Miocene epoch.
Del Valle Regional Park is a 4,316-acre recreational area centered around Lake Del Valle, a five-mile-long reservoir that serves as a terminal storage facility for the South Bay Aqueduct. The park is nestled in a valley of the Diablo Range, providing a varied landscape of oak-covered hills and expansive grassland. It acts as the gateway to the Ohlone Wilderness, a rugged 9,731-acre expanse designated for hiking and backpacking. The reservoir allows for motorized boating, sailing, windsurfing, and fishing, with a dedicated swimming area supervised by lifeguards during peak season. Wildlife observed in the park includes golden eagles, mountain lions, and bobcats. Geologically, the park sits near the Calaveras Fault, which influences the surrounding canyon topography. Visitors can utilize over 150 campsites ranging from primitive to developed sites with electrical hookups.
The East Beach overlook provides a panoramic view of the dam and the length of the reservoir.
Bring polarized sunglasses to reduce glare on the lake surface if you plan on fishing or boating.
Download offline maps before arrival, as cellular service is extremely spotty or non-existent in the valley canyons.
Check the East Bay Regional Park District website for blue-green algae alerts, which can periodically close swimming areas.
Attempting to hike the Ohlone Wilderness loop without a permit or adequate water supplies; swimming in non-lifeguard designated areas of the lake.
Park gates open earlier than the visitor center; swimming is restricted to specific beach areas and lifeguard-patrolled seasons.
Stay on designated trails to avoid ticks and poison oak; keep pets on a leash in developed areas and ensure they remain out of the water in non-designated zones.
