San Gabriel River and Montebello Forebay Water Conservation System


Since its inception in 1915, the Flood Control District, now Public Works, has made great strides in conserving water for Los Angeles County along the San Gabriel River, in the Montebello Forebay, and elsewhere. But storm runoff has increased with urbanization and more can be accomplished through extensive planning and improvement programs.

Spreading Ground Intake Structure ConstructionIt is estimated that the San Gabriel Canyon watershed generates about 1.3 million cubic yards (mcy) of sediment annually. Since construction of the Cogswell, San Gabriel, and Morris Dams in the 1930's, approximately 68 mcy of sediment has deposited in the three dams. Over the years, the Department has removed about 36 mcy, while 32 mcy of sediment remains trapped behind the dams. The accumulated sediment has resulted in a loss of flood control and water conservation capabilities at these dams. A sediment management plan has been developed that identifies methods and costs to remove the sediment so that water storage capacity can be maintained in the future.

Groundwater recharge improvements recently made or pending along the San Gabriel River include construction of intake structures to the San Gabriel Canyon Spreading Grounds, improvement of Santa Fe Reservoir Spreading Grounds, acquisition of abandoned gravel pits for spreading in the San Gabriel Valley, and increasing the spreading of reclaimed water.

The Montebello Forebay spreading facilities have recently undergone improvements with some work remaining including automation and telemetry facilities.

Long-ranged planning for Public Works's water conservation facilities will include consideration of improving aesthetics and providing for more recreation. However, the primary goal of the water conservation will continue to be maximizing water conservation capabilities to maintain the County's vital supply of groundwater.

Ducks at Spreading Grounds