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Stormwater Capture and Use – The Wave of the Future

By Ken Farfsing, City Manager, City of Signal Hill

This article was published in California Water in May of 2015.

The earliest settlers in Southern California relied on cisterns to collect and use rain water. Beginning in the early 1900s, Los Angeles County Flood Control planners designed flood control protections that had the added benefit of capturing and using rain water. Over the years, they designed and constructed 15 major dams in the local mountains and 27 spreading basins throughout the region, where captured stormwater can percolate and recharge our groundwater supplies. In wet years, active spreading, stormwater capture, and imported water recharges as much as 400,000 acre-feet of water in the San Gabriel River watershed alone.

Studies in the San Gabriel Valley illustrate the great potential of capturing and reusing even more stormwater and urban runoff throughout Southern California. Even with highly variable rainfall patterns, engineers estimate that between 10,000 acre-feet and 400,000 acre-feet of surface flow is lost each year to the Pacific Ocean, due to runoff being too turbid for recharge or exceeding the capacity of the dams and spreading basins. One acre-foot equals approximately 326,000 gallons of water, enough to supply three families with water for one year.

Capturing and using surface flow is critical. Individual homeowners, businesses and water utilities are helping out. The State Legislature passed the “Rainwater Capture Act” (AB 1750) in 2012 which allows homeowners and businesses to capture and reuse stormwater. New construction codes require and encourage landscaping that is drought tolerant and designed to capture rainwater in swales and ponds.

Local cities and the County of Los Angeles are embarking on a new program to capture and use the stormwater that is currently flowing to the Pacific Ocean. The County and the U.S. Bureau of Reclamation are studying ways to enlarge the dams and improve our existing regional system. The cities are examining ways to capture and reuse stormwater by constructing multi-use stormwater parks and “green streets,” and by capturing and percolating stormwater on-site. Hundreds of stormwater capture projects are now on the drawing boards, relying on existing open spaces, such as public parks, golf courses, and vacant land.

All of this has a cost. Funding and voter support for these programs is uncertain at this time. However, our region’s water future is even more uncertain if we do not support the new stormwater capture and use programs being planned. The county’s flood control planners in the 1910’s could never have envisioned that 10.1 million people would call Los Angeles County their home in 2015. We are facing the greatest water shortage in a generation, which will impact our children and grandchildren. The need to capture stormwater and develop local suplies is not only driven by the current drought, but also to support population and economic growth. We need to make the capture and use of more stormwater and urban runoff a top priority.

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