County of Los Angeles Department of Public Works
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Water


Flood Control
San Gabriel Dam Valve Release Operate and maintain 15 major dams and nearly 500 miles of open channel, 2,500 miles of underground storm drains, over 70,000 catch basins, about 300 debris retaining structures and 230 concrete stream bed stabilization structures, 40 pumping plants, and nearly 27 spreading grounds throughout Los Angeles County.


Water Conservation
Debris Basin Conserve each year in Los Angeles County an average of 220,000 acre-feet of local storm water runoff that would otherwise waste to the Pacific Ocean. This amount, valued conservatively at over $73 million, consists of direct storm runoff and post-storm releases from the dams. The water flows to 27 groundwater recharge areas, or spreading grounds, consisting of natural river bottoms and spreading basins and pits. During non-storm periods, the artificial recharge program is supplemented by spreading almost 75,000 acre-feet of untreated imported water and 50,000 acre-feet of reclaimed water.





Rio Hondo Spreading Grounds Operate and maintain three seawater barriers in Los Angeles County. These barriers inject treated imported water into the freshwater aquifers along coastal areas to prevent the intrusion of salt water inland. The aquifers protected by the barriers supply nearly 20 percent of the water used in Los Angeles County.


Engineering
Perform hydrology and sedimentation studies; collect stream flow, precipitation, and evaporation data; forecast runoff; analyze flood flows and take well measurements; manage reservoirs, debris basins and disposal areas; and prepare maps of watersheds burned by brush fires and potential mud flow areas.

Develop and direct the operation of the County's dams, spreading grounds, and seawater barriers; gather and disseminate hydraulic and hydrological data; create hydrologic computer models and build physical hydraulic models; perform frequency analysis of rainfall and runoff; and perform studies and improvement planning on facilities under its direction;

Engineer at Work Monitor and analyze water quality for surface and underground water to protect County flood control and water conservation facilities and to prevent contamination of the County's groundwater resources.