lake oroville

The FERC-licensed South SWP Hydropower facilities, also known as Project No. 2426 or P-2426, are located at the southern end of the California Aqueduct south of the Tehachapi Afterbay.

The West Branch carries water from the Oso Pumping Plant* into Quail Lake, the beginning of the P-2426 license boundary on the West Branch. Water enters the Peace Valley Pipeline which serves as a penstock for the William E. Warne Powerplant. The Warne Powerplant outflow is discharged into Pyramid Lake. Water from Pyramid Lake is diverted through the Angeles Tunnel and into Castaic Powerplant, owned and operated by the Los Angeles Department of Water and Power (LADWP). Water leaving the Castaic Powerplant enters the Elderberry Forebay, a key part of the Castaic Powerplant pump-storage operation and the southernmost end of the West Branch license boundary.

*Oso Pumping Plant is not part of the FERC license for P-2426.

The East Branch carries water from the Tehachapi Afterbay through Alamo Powerplant*, Pearblossom Pumping Plant*, and Mojave Siphon Powerplant* before entering Silverwood Lake, where the P-2426 license boundary begins on the East Branch. Silverwood Lake, formed by the Cedar Springs Dam, serves as a forebay to the Devil Canyon Powerplant. Water is diverted from the lake, through the San Bernardino Tunnel and then through two penstocks into Devil Canyon Powerplant and Afterbays, the southernmost end of the East Branch license boundary. Note that the Alamo and the Mojave Siphon Powerplants are generation facilities regulated through conduit exemptions.

*Alamo Powerplant, Pearblossom Pumping Plant and Mojave Siphon Powerplant are not part of the FERC license for P-2426.


The Department of Water Resources (DWR) submitted the original application for a preliminary permit to the Federal Power Commission (now FERC) on November 14, 1963. The Commission issued a preliminary permit on July 16, 1964 allowing planning to begin.

An important amendment to the application was the addition of LADWP as a joint applicant to the West Branch on July 10, 1967.

Original License: FERC issued an order on January 14, 1972 granting issuance of a 50-year license with conditions. The Final Environmental Impact Statement was then issued in June 1976 to comply with the National Environmental Policy Act.

The original license included 28 standard articles (Form L) and 27 other articles specific to the P-2426 license. In addition to these license articles, the original P-2426 license included 58 separate submissions called exhibits. Exhibits include maps, engineering drawings, environmental mitigation plan, recreational plan, and cultural resources management plan.

West Branch

Eaast Branch



Quail Lake Quail Dam and Lake provides regulatory water storage for power generation at Warne Powerplant during peak demand periods. Constructed in 1967, Quail Lake has an operating storage capacity of 7,580 acre-feet. When water is released, it flows from the lake through the Lower Quail Canal into Peace Valley Pipeline.

Pyramid Lake Peace Valley Pipeline serves as the penstock for Warne Powerplant. The pipeline is 5.5 miles long with a diameter of 12 feet and an overall capacity of 1,564 cfs.

Warne Powerplant generates power by taking advantage of the 725-foot drop through the Peace Valley Pipeline to Pyramid Lake. This plant has 2 generating units with a maximum rated capacity of 75 megawatts.
Castaic Powerplant Pyramid Dam is located on Piru Creek and was constructed between 1969 and 1973. The dam has a height of 400 feet, with a spillway for passing excess inflow into Piru Creek. The spillway consists of a concrete-lined channel controlled by a 40-foot wide by 31-foot high radial gate and a 365-foot long over pour weir with crest set 1 foot above the maximum operating water surface elevation of 2,578 feet.

Pyramid Lake has a maximum capacity of 171,200 acre-feet and serves as an afterbay for Warne Powerplant and forebay for Castaic Powerplant.

Angeles Tunnel Water from Pyramid Lake flows through the 30-foot diameter and 7.2 mile long Angeles Tunnel and generates power at Castaic Powerplant.
Pyramid Lake Castaic Powerplant, designed, built, and operated under a cooperative agreement between DWR and LADWP, is located at the northern end of Castaic Lake's west branch. Regulatory storage for Castaic Powerplant is provided by Pyramid Lake and Elderberry Forebay. Castaic Powerplant has 7 generators with a maximum rated capacity of 1,275 megawatts.

Water from Pyramid Lake flows through Castaic Powerplant into Elderberry Forebay, also operated by LADWP, and it can be pumped back through the plant into Pyramid Lake. This type of operation is called pumped storage. Elderberry Forebay has a maximum storage capacity of 32,480 acre-feet and also provides submergence of the pump-generator units when the lake is at its lowest operating levels. Elderberry Forebay is at the southernmost end of the West Branch FERC license boundary.


On the East Branch, the FERC Project (P-2426) includes Cedar Springs Dam, Silverwood Lake, the San Bernardino Tunnel and Devil Canyon Powerplant and afterbays.

Silverwood Lake formed by the 249-foot tall Cedar Springs Dam, is located at an elevation of 3,355 feet and is the highest reservoir in the SWP. The dam spillway is an ungated, 120 feet-wide, rectangular, lined chute located directly over the outlet works tunnel. The lake was constructed to provide regulatory and emergency storage with a maximum operating capacity of 74,970 acre-feet. The lake serves as an afterbay for the Mojave Siphon Powerplant and a forebay to the Devil Canyon Powerplant. From the south end of the lake, water is discharged into the San Bernardino Tunnel intake.
Devil Canyon Powerplant Devil Canyon Powerplant is a power recovery facility that receives water from Silverwood Lake via the 20,064 feet long, 12.75 feet diameter, San Bernardino Tunnel. Water flows from the tunnel into two parallel penstocks, each over one-mile long and is distributed to the powerplant. The 1,400-foot difference in elevation from Silverwood Lake, gives Devil Canyon the highest hydraulic head among the plants in the SWP. Flows in the Devil Canyon Powerplant discharge in the first afterbay, constructed from 1969 to 1974. The afterbay provides a nominal 49 acre-feet maximum amount of storage, so construction of a second 850 acre-feet afterbay began in 1992 and was completed in 1995. The second afterbay is connected to the first afterbay by a 152-foot wide overflow weir that discharges into a 1,100 feet long and 40 feet wide cross channel, increasing the powerplant's operational flexibility and capacity. The Devil Canyon Powerplant and Afterbays are at the southernmost end of the East Branch FERC license boundary.