Science

How to Conserve Water While Facing Down a Megadrought

Southwestern cities, facing an unending dry spell, are leading the way.

A boat sits on a cracked portion of dry land.
A formerly sunken boat rests on a now-dry section of lakebed at the drought-stricken Lake Mead on Tuesday in the Lake Mead National Recreation Area, Nevada. Mario Tama/Getty Images

This story was originally published by Yale Environment 360 and has been republished here as part of the Climate Desk collaboration. Reporting for this article was supported by a grant from the Water Desk, an initiative based at the University of Colorado Boulder’s Center for Environmental Journalism.

In the rolling hills around San Diego and its suburbs, the rumble of bulldozers and the whine of power saws fill the air as a slew of new homes and apartments rise up. The region is booming, its population growing at a rate of about 1 percent a year.

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This, in spite of the fact that Southern California, along with much of the West, is in the midst of what experts call a megadrought that some believe may not be a temporary, one-off occurrence, but a recurring event or even a climate change–driven permanent “aridification” of the West. The drought is so bad that last year federal officials ordered cuts to water provided to the region by the Colorado River for the first time in history.

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Water officials in San Diego, though, say they are not worried. “We have sufficient supplies now and in the future,” said Sandra Kerl, general manager of the San Diego Water Authority. “We recently did a stress test, and we are good until 2045” and even beyond.

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San Diego is not alone. While the public image may be that booming Southwestern cities such as San Diego, Phoenix, Las Vegas, and Albuquerque are on the verge of a climate apocalypse, many experts agree that these metropolitan areas have enough of a water cushion to not only survive but continue to grow into the surrounding desert for the foreseeable future, even during the worst drought in 1,200 years. Regardless of what the future holds, the search for water savings and more supply has so far been largely successful.

It’s a remarkable case of adaptation to climate change that flies under the radar—the result of a quiet revolution in recent years in how these cities source and conserve their water supplies. From replacing water-guzzling lawns with native vegetation, to low-flow plumbing fixtures, to water recycling and desalination, to the shift of agricultural water to cities, governments in arid Western regions are pursuing an all-of-the-above strategy.

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“When we had severe drought in the 1980s and early ’90s, we lost 32 percent of our supplies for 13 months,” said Kerl. “It had a devastating impact on our economy. And San Diego said, ‘Never again.’ ”

These major cities have reduced their use of water so much through conservation measures, as well as through creating new high-tech supplies, that they have so far been able to “decouple” the need for more water from growth. To be sure, the drought is taking a widespread toll on agriculture throughout the region as well as on cities and towns that lack aggressive conservation measures and have only a single source of water, whether that’s the Colorado River or groundwater. Page, Arizona, a town of roughly 7,500 people, could lose its municipal water supply if water levels in Lake Powell—already at historic lows—drop too far.

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There are also profound ecological effects of taking so much water out of a stressed system. “The [Colorado] River itself is bearing a huge burden for this, in terms of the environmental flows of the river,” said John Fleck, writer in residence at the Utton Center at the University of New Mexico School of Law. “Perhaps that’s the biggest cost, because we tend to give that part of the system short shrift. The environmental cost is substantial and probably not going away.” Among other things, low flows and warmer water often lead to the drying of riparian wetlands, endangering fish and wildlife.

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San Diego provides perhaps the best example of what cities are doing to make themselves drought-proof to continue business as usual in the face of deep water uncertainty. While such growth comes with serious problems—from traffic gridlock, to air and water pollution, to the destruction of nature—running out of water is not now on that list for most of the larger cities of the West.

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Beginning in the 1990s, the San Diego region embarked on one of the most aggressive water conservation plans in the country. An analysis last year showed that the city’s water use dropped from 81.5 billion gallons in 2007 to 57 billion gallons in 2020—a 30 percent decline. Nine cities surveyed in the Colorado River Basin lowered their water demand in the range of 19 to 48 percent between 2000 and 2015.

San Diego has pursued a multipronged approach. The city now requires an array of water-saving technology in new homes, such as low-flow toilets and showerheads. Perhaps the single biggest piece of the conservation solution is paying homeowners to tear out yards full of Kentucky bluegrass and replace them with far more water-efficient landscaping. The city-run program pays up to $4 a square foot for as much as 5,000 square feet, and so far has replaced 42 million square feet of water-thirsty lawns.

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Melanie Buck of Encinitas, a suburb of San Diego, tore out a grassy lawn and replaced it with a collection of desert plants, including asparagus ferns and several types of cactuses. “It’s quite a lot of maintenance” moving plants around as they grow, she said. “But our water bill is 50 percent less.”

Phoenix credits a similar program for its precipitous drop in water use. “In the 1970s, 80 percent of single-family homes had lush landscaping,” said Kathryn Sorensen, former water services director for Phoenix and now research director at the Morrison Institute for Public Policy, a think tank on water issues. “Today that number is 10 percent. It’s been a wholesale change in how people use water.”

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The key marker for residential use is gallons per capita per day. Right now, the average number of gallons used by homes that source their water from the San Diego County Water Authority is 135 gallons per capita per day, indoor and out, down from 235 daily gallons per capita in 1990—a 43 percent decline.

The new water future is not just about residential conservation—the overall strategy is diversification. “Just like you don’t want to put all of your eggs in one basket in your investment portfolio,” said Kelley Gage, director of water resources for the San Diego County Water Authority, “you shouldn’t do the same with your water portfolio.”

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At the time of the 1980s drought, San Diego had just one main source of water: the Metropolitan Water District, which brought Colorado River water to the city—across 242 miles of the Colorado River Aqueduct—to supply 95 percent of the San Diego region’s total. The rest came from local surface water.

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Officials embarked on a search for other sources. The agricultural sector uses about 80 percent of the water in the Colorado River, and so it is the place to which many cities and suburbs have turned to find more.

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San Diego’s single biggest source of water, secured two decades ago, is what is known as an ag-to-urban transfer. California was taking more of the Colorado River than its entitlement allowed, and in 2003, as part of an agreement that reduced California’s reliance on the Colorado River, San Diego agreed to fund water-saving irrigation improvements for the Imperial Irrigation District—the single largest user of Colorado River water—and to lease the water that was saved.

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San Diego paid to line with concrete the 82-mile All American Canal—the largest irrigation canal in the U.S.—and the Coachella Canal. Unlined canals lose up to 50 percent or more of their water to seepage, and lining can reduce that loss by 95 percent.

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San Diego also paid farmers to switch from flood to drip irrigation. All told, these measures freed up about 280,000 acre-feet of water. (An acre-foot provides two families with a year’s worth of water.) That transfer of savings from agricultural conservation is now the San Diego region’s largest single water source, with about 55 percent of its supply. Colorado River water is only 11 percent of the total these days.

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The San Diego County Water Authority has made large investments in “asset management”: the pipes that keep the water flowing. The county has 310 miles of large-diameter pipes—some of them up to 10 feet across—that deliver 900 million gallons of water a day. A major leak could spill large volumes of water in a short time, so monitoring the pipes and keeping them in good repair is an important part of conservation. Acoustic listening devices are a growing technology for saving water.

“We can go to a fire hydrant and listen for leaks,” said Martin Coghill, an operations and maintenance manager at the San Diego County Water Authority. If a leak is detected, technicians insert cameras, and in the case of the big pipes, they can lower someone in to inspect and do repairs.

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The concrete pipes the county uses have a fiber optic cable that runs inside the pipe. If any of the strengthening wires embedded in the concrete snap or otherwise break, the cable is designed to detect that sound and notify headquarters.

Water recycling is also playing an increasing role in water supply, in San Diego and elsewhere. Los Angeles has pledged to recycle all of its wastewater by 2035. Although San Diego’s climate is arid, with just 10 or fewer annual inches of precipitation, when rain does come the region captures 90 percent of the runoff in 24 reservoirs, and treats that precipitation to drinking water standards.

A growing amount of wastewater is also being recycled to drinking water standards. The city of Oceanside, near San Diego, just opened the first advanced water purification facility in the region that allows “toilet to tap” recycling, using ultrafiltration, reverse osmosis, and advanced oxidation to create 3 million gallons a day—about 20 percent of the city’s needs. The city of San Diego plans to have 40 percent of its potable water come from similar advanced recycling by 2035.

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San Diego County’s ace in the hole is North America’s largest desalination plant, capable of turning seawater into freshwater in about two hours to create 50 million gallons of potable water a day. The water is so pure that minerals have to be added to improve the taste. The downside is that it’s extremely energy-intensive to operate, a big part of why it is almost twice as expensive as imported water: $2,725 for an acre-foot versus $1,090 for imported water. Desalination also comes with serious environmental problems, including killing large numbers of fish, fish eggs, larvae, and plankton when the facilities suck in seawater.

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Las Vegas, where only 4 inches of rain falls each year, has dramatically upped its conservation game, and Clark County, which includes Las Vegas, has a robust cash-for-grass program that pays more than $32 a square meter. It also uses a series of hydrophones in its pipes to listen for leaks and repair them quickly. The technique was created by WaterStart, a Nevada-based think tank established by the Desert Research Institute and designed to accelerate the development of innovative water technology, as well as to help startup companies that work on water conservation technology become viable.

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Agriculture is also changing business. John Burr is a longtime avocado grower in Escondido, the heart of avocado growing in California. As he stood on a bluff above his avocado orchard, with a commanding view of the valley below, he explained how he and his daughter, Kyrsten, have brought precision agriculture to avocado growing.

First, they planted a high-density avocado orchard—400 trees per acre instead of 100—which cuts water needs in half. Dendrometers on the trees measure how much water the tree is taking up and how much it is losing to transpiration.

On Sunday mornings, John Burr looks at a spreadsheet on his computer. The California Irrigation Management Information System has 145 weather stations and two satellite systems that tell growers of all types how much water their crops have lost. “It pops out with how many inches of water we need to replace what was lost,” says Kyrsten Burr. “Then we can add precisely that much,” with microjets that only spray water around the tree. “It’s not only more accurate. It also makes sure we are getting what the plant needs.”

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Use has come down so much in California that Newsha Ajami, director of urban water policy at Stanford’s Water in the West program, says continued declines could upset water economics. “Everybody is still talking about investing in infrastructure,” she said. But officials need to better understand the demand for water, she says, which will continue to decrease as technology evolves.

For example, she said, California is “moving closer to small-scale recycling.” In San Francisco every commercial building over 100,000 square feet has to have an on-site recycling system that turns graywater from sinks and showers (not including sewage) into nonpotable water for toilets and irrigation. One building, the Salesforce Tower, treats both graywater and sewage, saving 30,000 gallons a day. And home water recycling units are now in the picture. Water use may drop so far “that utilities could end up with stranded assets or extra capacity that isn’t utilized,” Ajami said.

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How low can it go? “The decoupling can go on for a very long time,” says Fleck, especially in the U.S. where governments can afford the capital costs to assure alternative supplies. Las Vegas, for example, spent $1.5 billion to add a new outlet and massive pumps to assure a water supply from Lake Mead as levels drop. “I don’t think we know how long it goes on.” The question, he said “is at what point do cities become less livable because we have less green space around us.”

With all of these water conservation efforts, experts say that the future of cities like Phoenix, Las Vegas, and San Diego is a sufficiently wet.

“We know it’s a desert and we plan accordingly,” said Kathryn Sorensen. “Phoenix can survive dead pool”—the term for a nearly empty Lake Mead—“for generations. We have groundwater. We have done a good job of conservation and diversifying our portfolios. Desert cities are the oldest cities, and we will withstand the test of time.”

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