Castaic Dam is a dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 near the city of Castaic, California

Castaic, California

Castaic, California, is an unincorporated community and census-designated place in Los Angeles County, California, north of Santa Clarita and a few miles from Six Flags Magic Mountain amusement park. It is approximately 39 miles from the downtown Los Angeles Civic Center. As of the 2010...

. It is an earth-fill dam, though its surfaces are covered with boulder

Boulder

In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....

s and cobble

Cobble (geology)

A cobble is a clast of rock with a particle size of to based on the Krumbein phi scale of sedimentology. Cobbles are generally considered to be larger than pebbles and smaller than boulders . A rock made predominantly of cobbles is termed a conglomerate....

-sized rocks to prevent erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

. Although located on Castaic Creek

Castaic Creek

Castaic Creek is a stream in northern Los Angeles County, California. It is a tributary of the Santa Clara River.-Castaic Lake:Castaic Dam on the creek forms Castaic Lake, but most of the water comes from the West Branch of the California Aqueduct, also called the State Water Project. The lake is...

 and forming Castaic Lake

Castaic Lake

Castaic Lake is an artificial lake on Castaic Creek formed by Castaic Dam, in northwestern Los Angeles County, California, near the town of Castaic. The lake with a surface elevation of approximately above sea level is the terminus of the West Branch of the California Aqueduct, though some comes...

, Castaic Creek provides little of its water. The lake is the terminus of the West Branch of the California Aqueduct

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. The Department of Water Resources operates and maintains the...

, part of the State Water Project

California State Water Project

The California State Water Project, commonly known as the SWP , is the world's largest publicly built and operated water and power development and conveyance system. The SWP was designed and is operated by the California Department of Water Resources...

. The dam was built by the California Department of Water Resources

California Department of Water Resources

The California Department of Water Resources , is a department within the California Natural Resources Agency. The Department of Water Resources is responsible for the State of California's management and regulation of water usage...

 and construction was completed in 1973. The lake has a capacity of 325000 acre.ft and stores drinking water

Drinking water

Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

 for the western portion of the Greater Los Angeles Area

Greater Los Angeles Area

The Greater Los Angeles Area, or the Southland, is a term used for the Combined Statistical Area sprawled over five counties in the southern part of California, namely Los Angeles County, Orange County, San Bernardino County, Riverside County and Ventura County...

.

The 11 MW Foothill Feeder hydroelectric power plant is located at the base of the dam and generates electricity

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 when water is needed in Los Angeles

Los Ángeles

Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...

. The 1,495 MW (Nominal) Castaic Power Plant

Castaic Power Plant

Castaic Power Plant is a seven unit pumped-storage hydroelectric plant, operated by LADWP, which provides peak load power from the falling water on the West Branch of the California State Aqueduct...

 is located at the upper end of the West arm of Castaic Lake. Castaic Lake serves as the lower reservoir, while Pyramid Lake

Pyramid Lake (California)

Pyramid Lake is an artificial lake formed by Pyramid Dam on Piru Creek, near Castaic, California. The reservoir lies on the border between the Angeles National Forest and the Los Padres National Forest in the northwestern portion of Los Angeles County....

serves as the upper. When demand for electricity is high, usually during the afternoon, water is withdrawn from Pyramid Lake and released into Castaic Lake. At night, when demand is low, water is pumped back into Pyramid Lake. The sale of peak electricity reduces the Department of Water Resources' overall electric costs for operating the California Aqueduct.