The San Luis Reservoir is an

artificial lake A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

on San Luis Creek in the eastern slopes of the

Diablo Range The Diablo Range is a mountain range in the California Coast Ranges subdivision of the Pacific Coast Ranges in northern California, United States. It stretches from the eastern San Francisco Bay area at its northern end to the Salinas Valley are ...

Merced County, California Merced County ( ), is a county located in the northern San Joaquin Valley section of the Central Valley, in the U.S. state of California. As of the 2020 census, the population was 281,202. The county seat is Merced. The county is named after ...

, approximately west of Los Banos on State Route 152, which crosses

Pacheco Pass Pacheco Pass, elevation , is a low mountain pass located in the Diablo Range in southeastern Santa Clara County, California. It is the main route through the hills separating the Santa Clara Valley and the Central Valley. As with most passes in ...

and runs along its north shore. It is the fifth largest reservoir in California. The reservoir stores water taken from the San Joaquin-Sacramento River Delta. Water is pumped uphill into the reservoir from the

O'Neill Forebay O'Neill Forebay is a forebay to the San Luis Reservoir created by the construction of O'Neill Dam across San Luis Creek approximately west of Los Banos, California, United States, on the eastern slopes of the Pacific Coast Ranges of Merced Co ...

which is fed by the

California Aqueduct The Governor Edmund G. Brown California Aqueduct is a system of canals, tunnels, and pipelines that conveys water collected from the Sierra Nevada Mountains and valleys of Northern and Central California to Southern California. Named after Califo ...

and is released back into the forebay to continue downstream along the aqueduct as needed for farm irrigation and other uses. Depending on water levels, the reservoir is approximately long from north to south at its longest point, and five miles (8 km) wide. At the eastern end of the reservoir is the

San Luis Dam San Luis Dam is a major earth-filled dam in Merced County, California, which forms San Luis Reservoir, the largest off-stream reservoir in the United States. The dam and reservoir are located in the Diablo Range to the east of Pacheco Pass and ab ...

, the fourth largest embankment dam in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, which allows for a total capacity of . Pacheco State Park lies along its western shores. Completed in 1967 on land formerly part of Rancho San Luis Gonzaga, the reservoir is a joint use facility, being a part of both the

California State Water Project The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public wate ...

and federal

Central Valley Project The Central Valley Project (CVP) is a federal power and water management project in the U.S. state of California under the supervision of the United States Bureau of Reclamation (USBR). It was devised in 1933 in order to provide irrigation an ...

, which together form a network of reservoirs, dams, pumping stations, and of canals and major conduits to move water across California. The San Luis Reservoir is located in

Merced County Merced County ( ), is a county located in the northern San Joaquin Valley section of the Central Valley, in the U.S. state of California. As of the 2020 census, the population was 281,202. The county seat is Merced. The county is named after ...

, and has a visitor center located at the Romero Outlook where visitors can learn more about the dam and reservoir. The surface of the reservoir lies at an elevation of approximately , with the

below the dam at above sea level. This elevation difference allows for a hydroelectric

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...

to be constructed - the Gianelli Hydroelectric Plant.

Power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

from this plant is sent to a

Path 15 Path 15 is an portion of the north–south power transmission corridor in California, U.S. It forms a part of the Pacific AC Intertie and the California-Oregon Transmission Project. Path 15 is part of The Western Electricity Coordinating Cou ...

substation, Los Banos via a short

power line An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across large distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-p ...

. Those 500 kV wires, carrying both the power generated here and elsewhere, leave the area and cross the O'Neill Forebay on several man-made

island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...

s. San Luis Reservoir also supplies water to of land in the

Santa Clara Valley The Santa Clara Valley is a geologic trough in Northern California that extends 90 miles (145 km) south–southeast from San Francisco to Hollister. The longitudinal valley is bordered on the west by the Santa Cruz Mountains and on the east ...

west of the Coast Ranges. San Justo Dam stores water diverted from San Luis Reservoir through the Pacheco Tunnel and Hollister Conduit, which travel through the

. The Santa Clara Tunnel and Santa Clara Conduit convey water to the Coyote Pumping Station in the Santa Clara Valley.

History

San Luis Reservoir State Recreation Area

Banks of San Luis Reservoir in July 2021

San Luis Reservoir is part of the larger San Luis Reservoir State Recreation Area (

California State Parks The California Department of Parks and Recreation, more commonly known as California State Parks, manages the California state parks system. The system administers 279 separate park units on 1.4 million acres (570,000 hectares), with over 280 ...

) and therefore offers many recreational opportunities for fishermen, boaters, and campers. The park is patrolled by California State Park Peace Officers by vehicle, vessel, and off-highway vehicle. In addition to camping and boating, day use picnic areas are available at San Luis Creek, and an off-highway vehicle (OHV) area is available east of the main area at the intersection of Gonzaga Road and Jaspar-Sears Road. Camping is available at four campgrounds. * The Basalt Campground on the south-eastern edge of the lake with 79 developed family campsites. Water faucets are available nearby, and some sites can handle RV's to a length of . * San Luis Creek Campground on O'Neill Forebay with 53 sites with water and electric hook-ups. * Medeiros Campground has primitive campsites along the southern shoreline of O'Neill Forebay. This campground has drinking water at three locations and chemical toilets. * Los Banos Creek Campground has primitive campsites and limited turn-around space. It is not suitable for trailers or motor homes. Drinking water and chemical toilets are available. Improved boat launch ramps are offered at Dinosaur Point and the Basalt area. Due to the reservoir's water being imported from the Sacramento River Delta, San Luis shares many of its fish species with that area, including

largemouth bass The largemouth bass (''Micropterus salmoides'') is a carnivorous freshwater gamefish in the Centrarchidae ( sunfish) family, a species of black bass native to the eastern and central United States, southeastern Canada and northern Mexico, bu ...

, striped bass, crappie, bluegill, shad,

yellow perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Sam ...

, and occasional sturgeon and

salmon Salmon () is the common name for several commercially important species of euryhaline ray-finned fish from the family Salmonidae, which are native to tributaries of the North Atlantic (genus ''Salmo'') and North Pacific (genus '' Oncorhy ...

. The

California Office of Environmental Health Hazard Assessment The Office of Environmental Health Hazard Assessment, commonly referred to as OEHHA (pronounced oh-EEE-ha), is a specialized department within the cabinet-level California Environmental Protection Agency ( CalEPA) with responsibility for evaluatin ...

(OEHHA) has developed a safe eating advisory for fish caught in the San Luis Reservoir based on levels of mercury or

PCBs Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...

found in local species. The lake is noted for its high winds and has wind warning lights at Romero Outlook, Basalt Campground, and Quien Sabe Point.

Climate

The National Weather Service has maintained a cooperative weather station at San Luis Dam since 1963. Based on those records, average January temperatures are a maximum of and a minimum of and average July temperatures are a maximum of and a minimum of 64.0 °F. There are an average of 69.3 days with highs of or higher and an average of 14.1 days with lows of or lower. The record high temperature was on July 24, 2006, and the record low temperature was on December 22, 1990. Average annual precipitation is . There are an average of 57 days annually with measurable precipitation. The wettest year was 1998 with and the driest year was 1989 with . The most precipitation in one month was in February 1998. The most precipitation in 24 hours was on May 6, 1998. Snow rarely falls at the reservoir, but of snow fell on January 9, 2001.

References

External links

California State ParksThe Center for Land Use InterpretationCalifornia Dept of Water Resources Daily Reservoir Storage Summary

Gallery

File:SanLuis-2.jpg, San Luis Dam File:San Luis reservoir.jpg, San Luis Reservoir from Romero Outlook File:San Luis Dam and Gianelli Powerhouse.jpg, San Luis Dam and Gianelli Powerhouse File:Wfm san luis reservoir landsat.jpg, Satellite photo of San Luis Dam and the O'Neill Forebay {{authority control Reservoirs in Merced County, California California State Recreation Areas California State Water Project Diablo Range Parks in Merced County, California Central Valley Project Reservoirs in California Articles containing video clips Reservoirs in Northern California