L.A. River: Conflict Ahead as Water Capture, Restoration Plans Converge
EVERYONE KNOWS THE Los Angeles river. Even if it’s not part of your neighborhood, the concrete-lined channel is familiar worldwide, because nothing else in the movies or television better depicts “urban wasteland” than this drain.
But soon this stark, 51-mile (82-km) waterway may symbolize something else: tough choices amid water scarcity.
California’s historic five-year drought has prompted the Los Angeles region to look at using the river as a water supply – a role it has not served in over a century. Wastewater treatment plants, whose discharges now provide most of the river’s flow, may divert some of their treated effluent to groundwater recharge projects. Other plans are percolating to capture storm runoff before it reaches the river, both to recharge groundwater and improve water quality.
All these actions would leave less water in the river for two other important and fast-growing movements: improving wildlife habitat and expanding recreational opportunities.
A new report from the University of California, Los Angeles Grand Challenges program puts the conflict in stark terms: if all the currently envisaged stormwater capture and groundwater recharge projects go ahead, the L.A. river will be completely dried up, leaving no water for wildlife and recreation.
With careful choices, however, the 146-page report suggests, it may be possible to achieve all these goals.
To learn more, Water Deeply recently interviewed Katie Mika, the lead author and a postdoctoral scholar who grew up in the Los Angeles area.
Katie Mika: There are several plans to put in a variety of water-capture projects. They’re projects that could happen but won’t necessarily happen.
There’s a water capture master plan that the L.A. Department of Water and Power did. More than 100,000 acre-feet of stormwater capture projects have been identified in the region. Some are as large as identifying places to put in new spreading grounds [where water is retained to allow it to seep into the ground] to infiltrate stormwater into the groundwater basins. Then there are projects down to the parcel scale, using low-impact development approaches to capture or reuse stormwater on individual building sites.
Water Deeply: What are some examples of these projects?
Mika: One example is the Broadway Neighborhood Greenstreets Project, with a cistern that could capture water from upwards of 100 acres (40 hectares) of land. The projects that have been identified cover a huge range of scales, from a single dry well on one property up to many acres of spreading grounds.
One of the projects that’s definitely happening is at the Donald C. Tillman water reclamation plant, which discharges into the L.A. river. The city is looking to use up to 30,000 acre-feet of treated wastewater there to recharge groundwater via spreading grounds. That’s one of the biggest impacts that could happen on flow.
Water Deeply: Are there proposals now to start drawing surface water from the river again?
Mika: That isn’t part of the plan. One of the things that could be done is capturing a lot more stormwater before it gets into the river. And people are looking at places that we can divert water from the river to other places, like spreading grounds or treatment plants. So those still would likely be an indirect use of water in the watershed.
Water Deeply: How much water does the L.A. river carry today?
Mika: As kind of a ballpark number, the annual average flow of water going through the L.A. river is around 274,000 acre-feet per year. That would include the treatment plant flow and precipitation runoff. There might be a couple of places where there would be a tiny bit of infiltration, but most of that flow is being discharged to the ocean. And just for context, the city of Los Angeles total water supply tends to be between 500,000 and 600,000 acre-feet per year.