We conserve, recycle and desalinate water. Is capturing stormwater runoff the next big thing to try to ease California’s water woes?
The idea of putting treated stormwater runoff into the water supply has long been an intriguing notion in California. After all, rain and snow — essentially stormwater — feeds the state’s reservoirs. Runoff in urbanized areas — which is often polluted — doesn’t make it there and ends up flowing into waterways and the ocean, sometimes causing floods along the way.
The cost effectiveness of building infrastructure to channel stormwater into water systems often ended the discussion.
Nevertheless, the concept got a new boost from a study released last week as the state continues to struggle with an extended drought and increased costs of developing new sources of water.
The report by the Pacific Institute said California’s urban and suburban areas could create more sustainable water reserves through greater efficiencies, recycling and stormwater capture. The first two concepts are familiar practices, the last one less so.
The study was the latest take from the Oakland-based nonprofit think tank on how California can be more miserly with its precious, shrinking water supply. On the savings front, the institute’s researchers say California could reduce urban water use by 30 percent to 48 percent.
That’s a remarkable assertion, given California’s urban areas already have demonstrated a strong water conservation ethos. The report says total urban water use is about 6.6 million acre-feet a year, down from a peak of 10 million in 2007. San Diegans have cut their water use by nearly 40 percent over that same period, according to Joshua Emerson Smith of The San Diego Union-Tribune.
(For context, agriculture uses about 80 percent of the state’s water.)
An acre-foot of water is about 325,900 gallons, enough to cover an acre with 1 foot of water. The equation is continually changing with conservation efforts, but currently, the San Diego County Water Authority says an acre-foot can serve about 2.5 families of four for a year.
The Pacific Institute report mentions well-known ways water can be conserved, saying those methods can be applied more broadly and intensely. Among other things, the study lists low-water-use appliances such as washing machines and dishwashers (along with low-flow toilets), fixing leaks and continuing to replace lawns with drought-tolerant landscaping.
Leaks alone account for up to 10 percent of water use in homes and businesses, said Danielle Blacet, deputy executive director at the California Municipal Utilities Association, and Adrian Covert, senior vice president of public policy at the Bay Area Council. Advanced sensor technology has made leaky pipes easier to find.
The institute’s report said the state currently recycles nearly a quarter of urban wastewater, some 728,000 acre-feet.
“We estimate that an additional 1.8 million to 2.1 million (acre-feet annually) of municipal wastewater is available for reuse in California,” the report said.
The city of San Diego’s Pure Water wastewater recycling program eventually is expected to provide half of the city’s potable water.
The use of stormwater also could become a major source for the state, the report says. The researchers say the potential stormwater capture in a dry year would be 580,000 acre-feet and 3 million in wet years. The Pacific Institute discusses putting stormwater runoff in underground aquifers and other storage areas. The report says there are no current estimates of how much stormwater is being put into the water supply, but some jurisdictions are doing it.
According to the Los Angeles Times, the Pure Water Monterey project treats wastewater and storm runoff to replenish groundwater. The Fresno flood control district operates stormwater retention basins.
California has been experiencing extended droughts and is expected to do so in the future. But projections also include periods of heavy rain as “atmospheric river” conditions intensify.
The city of San Diego and local jurisdictions across California are facing increasing mandates from the state to manage stormwater runoff. Even without the state pressure, much of San Diego’s water drainage infrastructure is old and needs to be upgraded.
The city’s needed water quality and stormwater projects are estimated at $1.8 billion. Officials are contemplating asking voters to increase taxes to pay for the upgrades, contending that if they are not made, emergency cleanups may cost even more. In addition to flooding, local governments need to keep stormwater pollution and debris out of the ocean and waterways.
Drinking water and stormwater systems were built separately for obvious reasons. Connecting the two could take a lot of costly infrastructure — something San Diego isn’t planning — to capture the water and direct it to be treated.
Adding to the water supply and ensuring its reliability has long had appeal, but maybe not as much locally these days for the simple reason that regional water officials say the county already has guaranteed water to meet demand for years to come. Further, there are growing complaints the region doesn’t need all the water it is obligated to pay for.
So, for now, maybe the idea of making stormwater into drinking water might be a tough sell here, especially with water bills on the rise.
Statewide, though, the Pacific Institute believes that and the conservation, recycling and stormwater measures are the way to go.
“California can fill the gaps between water supply and use with strategies that are technically feasible, cost effective, and compatible with healthy rivers and groundwater basins,” the study concludes.
The feasibility of tapping new, more expensive water sources often is doubted, at least at the outset.
Years ago, wastewater recycling and desalination didn’t pencil out, but now circumstances make the costs more acceptable — though some critics still say they’re too expensive and too energy intensive. It’s unclear where stormwater would fit into this dynamic.
But one thing we’ve learned in recent decades is that water economics are rarely static.
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Originally Appeared Here