O'Neill Forebay is a forebay

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 to the San Luis Reservoir

San Luis Reservoir

The San Luis Reservoir is an off-stream artificial lake in the eastern slopes of the Diablo Range of Merced County, California, approximately west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its north shore. The reservoir stores water taken from the San...

 created by the construction of O'Neill Dam

O'Neill Dam

O'Neill Dam is an earthfill dam on San Luis Creek, west of Los Banos, California, on the eastern slopes of the Pacific Coast Ranges of Merced County...

 across San Luis Creek

San Luis Creek (California)

San Luis Creek, originally Arroyo de San Luis Gonzaga, is a stream in Merced County, California. Its source is located in Merced County, about 1000 ft. northwest of 3448 ft. high Mariposa Peak, on the Merced County - San Benito County boundry and 7.4 miles south of Pacheco Pass...

 approximately 12 miles (19.3 km) west of Los Banos, California

Los Banos, California

Los Banos is a city in Merced County, California, near the junction of State Route 152 and Interstate 5. Los Banos is located southwest of Merced, at an elevation of 118 feet . The population was 35,972 at the 2010 census, up from 25,869 at the 2000 census...

, on the eastern slopes of the Pacific Coast Ranges of Merced County

Merced County, California

Merced County , is a county located in the Central Valley of the U.S. state of California, north of Fresno and southeast of San Jose. As of the 2010 census, the population was 255,793, up from 210,554 at the 2000 census. The county seat is Merced...

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Background

Roughly 2.5 miles (4 km) downstream from the San Luis Dam

San Luis Dam

San Luis Dam is a dam that creates San Luis Reservoir, which serves as an off-stream reservoir for the California State Water Project and the Central Valley Project. It is also known as the B.F. Sisk Dam, after Bernie Sisk. The earth-fill gravity embankment dam is 305 feet tall and was completed...

, O'Neill Forbay collects irregular water releases from the San Luis Dam and William R. Gianelli Powerplant in its 56400 acre.ft basin. A morning-glory type spillway lies at the left bank of the reservoir. The reservoir is fed by releases from the San Luis Dam as well as from the Delta–Mendota Canal. Water from the Delta–Mendota Canal is lifted a vertical distance of 8 feet (2.4 m) into a channel running 2200 feet (670.6 m) into the forebay.

O'Neill Dam

O'Neill Dam, constructed from 1963 to 1967, is an 87.5 feet (26.7 m) high, earthfill and rockfill dam, stretching over three miles (5 km) across the valley of San Luis Creek. With a maximum reservoir depth of 57 feet (17.4 m), peak inflow to the forebay is 15600 ft3 per second, from both the San Luis Dam and the Delta–Mendota Canal. Drainage area of the reservoir downstream of the San Luis Dam is only 18 acre (0.07284348 km²). The O’Neill Pumping-Generating Plant produces 28,000 kilowatts.

Recreation

Notably, the largest striped bass

Striped bass

The striped bass is the state fish of Maryland, Rhode Island, South Carolina, and the state saltwater fish of New York, Virginia, and New Hampshire...

 caught in California was caught in the O’Neill Forebay. The fish, 52.5 inches (133.4 cm) long and weighing 70.6 pounds (32 kg), was caught on August 5, 2008 by Frank Ualat of Gilroy, California

Gilroy, California

Gilroy is the southernmost city in Santa Clara County, California, United States. The population was 48,821 at the 2010 census. Gilroy is well-known for its garlic crop and for the annual Gilroy Garlic Festival, featuring various garlicky foods, including garlic ice cream. Gilroy also produces...

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