San Gabriel River and Montebello Forebay Water Conservation System
hen San Gabriel River water is released from the canyon facilities, it flows to the Santa Fe Dam, a compacted earth-fill dam owned by the Corps, rising 92 feet in height and spanning 23,800 feet in length at the crest. In the upper portion of the reservoir is the Santa Fe Spreading Grounds. This excellent spreading facility, which Public Works operates under license from the Corps, can percolate approximately 400 cubic feet per second continuously. A rubber dam, built in 1995, is used to direct flows from the San Gabriel River into the Santa Fe Spreading Grounds. The San Gabriel River downstream of Santa Fe Dam was constructed as a soft bottom channel to promote infiltration of water released from the dam during large storms or for spreading.
A rubber dam, built in 1994, is located in the San Gabriel River near Valley Boulevard. This rubber dam creates a 76-acre, 495 acre-foot spreading facility within the San Gabriel River and Walnut Wash.
The Whittier Narrows Dam, also owned by the Corps, captures water flowing in the San Gabriel River and Rio Hondo Channel. Whenever the primary objective of flood control is not compromised, controlled released of water from Whittier Narrows Dam continue to Public Works' Coastal Plain spreading grounds.
In addition to spreading storm water, MWD provides imported water to Public Works for groundwater recharge in cooperation with the Main San Gabriel Basin Watermaster and the Central and West Basin Municipal Water Districts. Pictured below is Central Basin Connection No. 48, a MWD outlet that can release water to San Dimas Wash and then through the downstream flood control system to the Montebello Forebay. Another agency that provides imported State Water Project water for spreading is the San Gabriel Valley Municipal Water District, which has its own delivery pipeline. About 75,000 acre-feet of untreated imported water purchased by local water agencies are spread annually.
A further aspect of the water conservation program is spreading recycled water from facilities such as Whittier Narrows, San Jose Creek, and Pomona Water Reclamation Plants owned by the Sanitation Districts of Los Angeles County. Planned replenishment using recycled water has been practiced in the Montebello Forebay area since 1962. Currently, about 50,000 acre-feet of recycled water is spread each year on behalf of the Water Replenishment District of Southern California. Plans are under way to spread 10,000 acre-feet of recycled water in the San Gabriel River below Santa Fe Dam on behalf of the Upper and San Gabriel Valley Municipal Water Districts.