Castaic Creek is a 25 miles (40.2 km) stream in northern Los Angeles County, California

Los Angeles County, California

Los Angeles County is a county in the U.S. state of California. As of 2010 U.S. Census, the county had a population of 9,818,605, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states...

. It is a tributary of the Santa Clara River

Santa Clara River (California)

The Santa Clara River is approximately long, located in southern California in the United States. It drains an area of the coastal mountains north of Los Angeles. The Santa Clara is one of the largest river systems along the coast of Southern California and one of only a few remaining river...

.

Castaic Lake

Castaic Dam

Castaic Dam

Castaic Dam is a dam near the city of Castaic, California. It is an earth-fill dam, though its surfaces are covered with boulders and cobble-sized rocks to prevent erosion. Although located on Castaic Creek and forming Castaic Lake, Castaic Creek provides little of its water. The lake is the...

 on the creek forms 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...

, but most of the water comes from 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...

, also called the State Water Project. The 323700 acre.foot lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 is the terminus for west branch of the aqueduct

Aqueduct

An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

. The aqueduct delivers water to the lake by a pipeline from 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....

.

Besides storing 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...

, Castaic Lake is the lower reservoir in a pumped-storage hydroelectric

Pumped-storage hydroelectricity

Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...

 system. During times of peak 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...

 demand, water is released from Pyramid Lake and run through the turbines

Water turbine

A water turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy...

 at Castaic Power Plant. At night, when demand and electricity prices are lower, water is pumped from Castaic Lake to Pyramid Lake. The income from the electricity sold offsets a portion of the cost for pumping the water in some parts of the aqueduct, such as over the Tehachapi Mountains

Tehachapi Mountains

The Tehachapi Mountains , regionally also called The Tehachapis, are a mountain range in the Transverse Ranges system of California in the Western United States...

.

Creek resumes

Some water is released into Castaic Lagoon, immediately downstream of the dam. The lagoon provides Groundwater recharge of the aquifer

Aquifer

An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

 and recreation. Downsteam of the lagoon, water continues in Castaic Creek through the Sierra Pelona Mountains

Sierra Pelona Mountains

The Sierra Pelona Mountains , or the Sierra Pelona Ridge, is a mountain range in the Transverse Ranges of Southern California.. They are located within Los Angeles and Kern Counties.-Geography:...

 to its confluence with the Santa Clara River, a few miles west of Santa Clarita

Santa Clarita, California

Santa Clarita is the fourth largest city in Los Angeles County, California, United States and the twenty-fourth largest city in the state of California. The 2010 US Census reported the city's population grew 16.7% from the year 2000 to 176,320 residents. It is located about northwest of downtown...

. The rest is distributed to the northern 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...

by pipelines.