Whittier Narrows Dam and Reservoir is a flood control and water conservation project constructed and operated by the U.S. Army Corps of Engineers, Los Angeles District at the Whittier Narrows in Montebello, California. Whittier Narrows Dam is a central element of the Los Angeles County Drainage Area (LACDA) flood control system. The Dam and Reservoir serve to collect runoff from uncontrolled drainage areas upstream as well as releases into the San Gabriel River.
The primary purpose of the Dam is flood risk management. The Corps acquired 2,640.1 acres in fee and has limited rights over an additional 186.5 acres through a flowage easement. The Corps reserves 869.4 acres exclusively for operation of the Dam. The remaining 1,770.7 of fee acres are available for compatible purposes with a preference toward recreation development.
Construction of the dam was completed in October 1957. The San Gabriel River and Rio Hondo flow into the Reservoir bringing flows collected from a 554 square mile drainage reservoir. The two river systems flow parallel in the Reservoir, but do not convene. Although there is a significant amount of water released into the San Gabriel River from the Dam, most of the water released from the Dam is through the outlet works into the Rio Hondo. Releases from the Dam outlet works to the Rio Hondo are limited to a maximum of 41,000 cfs.
For detailed physical data visit the Reservoir Regulation page. Additional information on Whittier Narrows Dam and Reservoir can be found in the Whittier Narrows Basin Master Plan.
Keep yourself safe when visiting the many public facilities in the reservoir by being aware if the potential for storms is being forecast. The Reservoir is designed to hold back large quantities of water and can fill very quickly. Check the local weather forecast before enjoying the many recreational opportunities in and around the reservoir.
The Corps evaluates environmental effects of all actions taken at the Dam and in the Reservoir. Biological surveys are conducted in the Reservoir throughout the year by the Corps and the Corps partner agencies.
Many wildlife species are found within the Reservoir. The open water areas found in the Reservoir attract waterfowl and shorebirds such as great egrets (Ardea) and ruddy ducks (Oxyura jamaicensis). Riparian and upland habitats host a diversity of passerine species such as black phoebe (Sayornis nigricans) and California towhee (Melozone crissalis). Bat species are also present and use the Reservoir for roosting, breeding, or as year-round residents. Only two amphibians are common, including the California toad and Pacific tree frog. Dry upland areas host common lizard and snake species.
Native vegetation identified in the Reservoir includes sandbar, narrowleaf, and coyote willow (580.1 acres or 22.0% of the Reservoir). Non-native habitat types are present in the Basin and include ornamental tree/maintained lawn (804.2 acres or 30.5% of the Basin), disturbed upland (333.0 acres or 12.6% of the Basin), agricultural land (76.2 acres or 2.9% of the Basin), and ruderal land (573.9 acres or 21.7% of the Basin).
The Corps engages in routine maintenance activities within the operational areas of the Reservoir year round to maintain the operational capacity of the project. As congressionally appropriated funding allows, the Corps works to upgrade aging structures and systems. Annual maintenance activities at US Army Corps of Engineers operated dams include grading of access roads, vegetation removal, and an annual safety inspection. In addition, the control house, gates, and all mechanical and electrical equipment is checked at each dam to make sure that it is functioning in accordance with the Dam Operations Manual. Graffiti removal, clearing of debris and sediment, and additional repairs are performed to maintain the facility.
Review Upcoming Proposed Actions
To review public notices on our upcoming proposed maintenance activities please visit the Public Notice postings page or click the “Public Notice” link found in the navigational side bar.
Questions, Concerns, Comments?
Let us know by filling out the comment form or click the “Contact” button in the navigation bar and choose Asset Management (Real Estate | Recreation) or Asset Management (Facility Operations | Maintenance) as the recipient.
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