San Pablo Reservoir, drinking water reservoir in Contra Costa County, California, USA

San Pablo Reservoir is an open-cut terminal storage reservoir in the San Pablo Creek valley between San Pablo Ridge and Sobrante Ridge, north of Orinda in Contra Costa County. Its water forms irregular branching arms reaching into dry tan ground and dark green trees, with the earthen San Pablo Dam at the El Sobrante end. The reservoir holds 38,600 acre-feet and drains a 23.37-square-mile watershed.

The earthen San Pablo Dam was built in 1919 at the El Sobrante end of the reservoir, above Kennedy Grove. Most of the water is imported through the Mokelumne Aqueduct from Pardee Reservoir in the Sierra Nevada foothills. After a 2004 study found the dam could settle up to 35 feet in a Hayward Fault earthquake, the reservoir level was lowered by 20 feet, and a seismic retrofit ran from August 2008 to September 2010.

The reservoir is a drinking-water storage facility, so swimming and wading are banned while fishing, boating and canoeing are allowed; only four-cycle engines using MTBE-free gasoline may be used. The San Pablo Grill and a gift shop, where fishing permits are sold and boats rented, sit in the recreation area. Since May 2015 the Oakland Strokes have held the USRowing Southwest Masters Regional Championships here.

Access is from San Pablo Dam Road along the west side; the recreation area charges a daily entrance fee. Swimming and wading are prohibited because the reservoir stores drinking water. Only four-cycle engines using MTBE-free gasoline are allowed on boats. A 5.5-mile hiking and biking trail follows the west shore, mostly on the Old San Pablo Dam Road; a full loop around the water is not legally possible.

Since May 2015 the Oakland Strokes have organized the USRowing Southwest Masters Regional Championships on the reservoir, and it was proposed as the rowing and canoe venue had San Francisco hosted the 2024 Summer Olympics. The reservoir is also stocked with trout and catfish for anglers.