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StumbleUponAnother Dust Bowl?
In the West, it's long been understood that there will never be enough rain and that the solution is to make existing stocks of water go further. Western writer and environmentalist Wallace Stegner captured this fact of life eloquently: "Water," he wrote, "is the true wealth in a dry land."One of the most vital sources of water in the region is Lake Mead, a vast reservoir some 25 miles east of Las Vegas that was created during the construction of Hoover Dam, a spectacular engineering project that tamed the mercurial Colorado River, brought hydroelectric power to a region considered uninhabitable without air-conditioning, and allowed the desert to bloom with everything from ranches to casinos. As the reservoir was formed, the remnants of an ancient Native American settlement, dubbed the Lost City, were submerged.
Lake Mead is part of the Colorado River system, which also includes Lake Powell, a second huge reservoir some 150 miles east, on the Utah-Arizona border. Fed by melting snow from the Rocky Mountains, the Colorado system is the main source of water for 30 million people in the Southwest. Millions more in California and Nevada rely on water from the Sierra Nevada. But a stretch of unusually dry years has driven levels in Mead and Powell to near-record lows. Today, as Lake Mead dries up, the ruins of the Pueblo Indians' Lost City have reemerged, an eerie emblem of the drought.
As in the Southeast, population growth is a hazard. During the 1990s, Nevada's population jumped by 66 percent, the fastest rate in the nation. Arizona was the second fastest, at 40 percent, with Utah and Colorado clocking in at 30 percent—more than twice the national average. This growth will likely continue at an even faster clip in the future. Nevada and Arizona alone are expected to double their populations by 2030.
There's another climatic player: global warming. Growing scientific evidence warns that climate change could render the Southwest's growth and development trends untenable.
Here's why: Unlike the Southeast, where most precipitation comes as spring and summer rainfall, in the West those months are written off as a dry season. "We get all of our water in the winter from frozen precipitation," says Underwood, the Nevada climatologist. The snowstorms that blanket the West's mountain ranges each winter form a thick snowpack. As that snow melts in the spring, it feeds streams and tributaries to replenish Lakes Powell and Mead and other, smaller reservoirs. The reservoirs draw down gradually through the warmer months, and the process begins again.
Timing is everything. "We want that snow to stay on the mountainside and melt nice and slow into our reservoirs," says Underwood. If warmer temperatures cause the snow to melt too soon or too fast, small reservoirs can't catch and hold the runoff. That means water that would ordinarily be saved for summer use is wasted. "You're losing part of your bank account," adds Fuchs. Worse, some of that precipitation may come in the form of rain, causing two problems: flooding and water that can't be stored. Early runoff isn't an issue for Powell and Mead, whose huge size allows them to store whatever water comes their way. But early springs and higher year-round temperatures cause other problems. More water is lost through evaporation, and a longer warm season increases demand on the system. "We're always worried about it warming up too quickly," says Underwood.
That's where climate change comes in. In recent decades, increasing temperatures in the West have led to more winter rain, less snow, earlier snowmelts, and higher evaporation rates—a cascade of bad news for the region’s water supply. Now a new study has confirmed what climatologists have long suspected. Analyzing 50 years of data, scientists at the University of California, San Diego, and elsewhere report that these changes have resulted mainly from human activity and are likely to intensify in the future. The researchers postulate that global warming is also responsible for the long-term drop in precipitation in the West, though this is less certain. In a second study, some of the same scientists estimated that if current climate and water-management trends continue, Lake Mead has a 50 percent chance of running dry by 2021.
"If the climate changes as projected, the West will have to make do with less water or find new sources," says study co-author David Pierce. Brian Fuchs goes further, raising the specter of "a new Dust Bowl" unless major changes in water use and management occur. This ominous historical reference is to the Depression-era drought that drove millions of Americans off their farms in Oklahoma and other Great Plains states—many of whom ended up, ironically, in California.
Is the glass half full?
Amid the gloomy projections, the West recently received some good news. Last winter brought above-average snowfall, and hydrologists were predicting that the water level in Lake Powell could rise by as much as 50 feet, which would bring it to about 65 percent of capacity.
While experts caution that it will take more than one robust snow year to end the drought, there are signs that regional government officials and ordinary citizens are starting to heed scientists' warnings. California is leading the way. The Metropolitan Water District of Southern California, for instance, is nearing completion of a 12-foot-wide, 44-mile-long pipeline designed to catch the runoff caused by increased rainfall and earlier snowmelts—water that would otherwise be wasted. At a cost of more than $1 billion, the underground pipeline, known as the Inland Feeder, will rush water originating in the Sierra Nevada to Southern California at a rate of 7,500 gallons per second.
In Orange County, water officials recently unveiled an innovative project that converts millions of gallons of sewage water into drinking water. Using high-tech purification techniques such as reverse osmosis and microfiltration, the Groundwater Replenishment System, uninvitingly known as toilet-to-tap, produces up to 70 million gallons of clean water a day. Conservation is crucial too. In the Los Angeles area, the population served by the regional water district has increased 4 million since 1990. But water consumption levels remain the same, thanks to changes citizens have been urged to make, such as replacing grass lawns with native plants that need less water and installing low-flush toilets, low-flow showerheads, smart lawn sprinklers, and high-efficiency washing machines.
State governments are beginning to do their part as well. Last December, the seven states that rely on the Colorado River system reached a historic agreement to better manage the water supply and mitigate the effects of drought. Under the deal, which officials hope will end 85 years of interstate wrangling, a system of de facto water rationing will kick in when Lake Mead reaches established trigger levels. The flow of water from Lake Powell downstream to Lake Mead will be more effectively regulated to maintain sufficient levels in both reservoirs, and states will be allowed to "bank" water reserves in Lake Mead for future use, replacing the previous use-it-or-lose-it policy.
Many water watchers hope that the Southeast will follow the West's lead. Aiming to match the achievement of their counterparts across the country, the governors of Georgia, Florida, and Alabama have been negotiating a new water-sharing plan. That would help. But Georgia climatologist Stooksbury says what's really needed is a major attitude adjustment. Perhaps it's already taking place. After past droughts, his region reverted to old habits once the rains returned. He thinks things may be different this time. "We're all aware now that we're going to have to treat our water as a valuable commodity," he says.
That's a lesson everyone can take to heart. After all, when it comes to another vital resource, oil, we can at least imagine a world powered by solar panels, windmills, and other energy sources. But water is one substance we can't live without.
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