Home gardeners from across San Diego gathered on Sunday (March 20) for an event hosted by water-quality watchdog San Diego Coastkeeper to discuss the potential impact of rainwater capture in the face of the region's ongoing drought.
The seminar (billed "Capturing the Storm" in anticipation of heavy El Niño rains that have yet to deliver an expected deluge) is part of an ongoing Signs of the Tide educational series presented by Coastkeeper.
"A lot of people have bought into the 'buy local' food movement, seeking products produced within 100 miles of home. We're hoping to do the same thing with much of our water," says Travis Pritchard, Coastkeeper's interim executive director. "I did the math and we're bringing in about 137 billion gallons a year — that's a lot of water, roughly the amount of oil transported by ship worldwide."
According to figures provided by presenters, San Diego imports as much as 72 percent of its water supply. While a new desalination plant in Carlsbad is expected to boost the locally produced supply by up to 8 percent, it comes at the cost of energy consumption equivalent to 28,500 residential homes. And if just a portion of local residents were to resort to capturing rainwater for irrigation purposes, it could potentially have more than double the effect of what's billed as the Western Hemisphere's largest desalination plant on decreasing water-import needs.
"We've had a lot of people criticize our policies that encourage the use of rain barrels because, as everyone knows, it never rains here. But it does rain — why not take advantage of that free water coming from the sky?" asked Marsha Cook, an environmental health specialist with the county. "Are rain barrels the solution to all of our water issues? They're really not, but if we can get people thinking about water conservation through their use, it's a way to get the conversation started."
Cook shared figures of her own: during a rainstorm that deposits 1" of water, a home with 1000 square feet of roof could capture as much as 625 gallons of water, enough to irrigate a small orchard of five to six citrus trees for a month.
She also stressed that rebates are available from Metropolitan Water District, the Los Angeles–based wholesaler that supplies San Diego with its imported water, in the amount of $75 per barrel, up to a maximum of $300 for four barrels or 300 gallons' total capacity. In the 2013–2014 fiscal year, Metropolitan paid over $150,000 in rebates to county residents. City residents can pile on with another $1/gallon for installing up to 400 gallons' worth of rainwater capture.
"It's not free, but it's pretty close," said Cook of the cost of adoption after factoring in available rebates.
Brook Sarson, founder of rainwater and graywater recycling firm H2ome, told attendees that although rainwater capture in a dry climate seems insignificant, big changes in overall water consumption are achievable through tweaks to landscaping style and taking advantage of water when it's available.
"Most of our residential water use is actually in our yards, so that's the key place we can cut back on our water," said Sarson, but "we don't have to turn our landscapes into deserts. We don't live in a desert — we live in a Mediterranean climate. We don't live in cactus and gravel here."
"If you use Southern California native plants, you could in theory have your landscape survive without any supplemental water at all," added UCSD biologist Steve Miller, a native vegetation expert. "There's tons of variety in native plants — San Diego is, plant-wise, one of the most biologically diverse counties in the country."
One way or another, panelists agreed, San Diego has to cut its water consumption, particularly from imported sources. According to cited figures, the average San Diegan uses about 140 gallons of water a day, with much of this use directed toward landscaping and other outdoor use.
By comparison, the U.S. average is 94 gallons per person, while in Tijuana and other water-strapped climates like Brisbane, Australia, the average is closer to 40 gallons a day. Our average spikes still further due to the inclusion of the wealthy enclave of Rancho Santa Fe, which uses 400–600 gallons of water per person per day, mostly to irrigate lawns, golf courses, and other ornamental landscaping.
"San Diego is paying farmers not to farm so we can have their water," says Pritchard. "And the water we bring in needs to be pumped over mountains; if you think about what it takes to bring this water into the region just to pour it on a lawn, it seems like a really silly use of resources."