The great American cities of the desert Southwest were never built on sand. They were built on water.

Los Angeles, Phoenix, Las Vegas, and lesser cities such as Tucson have all floated upward over the last century on an illusion that water in the largely arid region could be as plentiful and cheap as it was in the much wetter East.

In one of the great feats of human engineering, huge dams, massive reservoirs, hundreds of miles of canals, and aqueducts have been constructed to sustain that illusion. But today, in the midst of a historic drought, with a still-growing population draining the region’s rivers and aquifers, the foundation of the Western dream is evaporating. A day environmentalists have long warned was coming seems to have arrived: a reckoning for the West’s profligate, crop-irrigating, lawn-watering, swimming-pool-filling, golf-course-building ways.

But looming disasters have at least one advantage. They upset established thinking. For years, an unlikely assortment of conservationists, architects, and land-use planners have been working on an alternative vision of life in the West, one that embraces using smarter urban design and landscape planning to live on far less water than contemporary urban civilization now consumes.

In the beginning they were often dismissed as eccentric prophets. Today, they are heralds of changing attitudes about water use. “Clearly the drought is cooperating beautifully with the desire to grab the public’s attention on what is likely to be a long-term condition, not a mere episode,” observes Hadley Arnold, a Los Angeles architect who works on water management, somewhat wryly.

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Hadley and her husband and fellow architect, Peter, founded the Arid Lands Institute at Woodbury University in Burbank, California in 2008 to help build a water-smart urban environment in the American West that can serve as a model for the rest of the world. “Divining LA: Drylands City Design for the Next 100 Years” is the institute’s ongoing effort to rethink how we design our buildings, neighborhoods, and cities to take the greatest possible advantage of the rainfall the area receives.

As the Arnolds outlined in Boom magazine, the process involves a deeper understanding of how stormwater moves through an urban landscape, including both where it can be harvested and how it is being lost. In places where water can replenish the aquifer, the proper landscaping and vegetation can make sure it has time to infiltrate the soil. In other areas, water needs to be channeled to productive areas.

While it may seem unlikely that Los Angeles, the quintessential sprawling Western city, could significantly reduce its dependence on outside water, the city has estimated it could provide for 82 percent of its water needs through efficient recycling and stormwater capture. The Arnolds’ studies indicate the San Fernando Valley alone could capture enough stormwater runoff to provide for nearly 100,000 homes.

These ideas have been gaining credibility in water-use circles for several years, but as conditions have worsened they have become a part of a passionate discussion about how the West can manage water more efficiently. Recently, the Arnolds have seen a marked change in the reception to their ideas among city officials, land-use planners, and especially professionals in the building industry. “Ten years ago, we had to answer the ‘what does this have to do with architecture?’ question with some frequency,” says Hadley. “We’re not asked that question anymore.”

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About 500 miles southeast of Los Angeles in Tucson, Arizona, Brad Lancaster has been working for more than 20 years to convince his desert city it could largely subsist on the 11 to 12 inches of water that falls from the sky annually.

His mission is the same as the Arnolds, but his approach is personal. At his small home in an old Tucson neighborhood, Lancaster lives almost exclusively on water he captures off the galvanized metal roofs of his and his brother’s house. He also raises a flourishing garden and a collection of trees through smart water harvesting. Combined with reusing “greywater” for irrigation and careful conservation, he exists with minimal reliance on the city’s water system.

Lancaster grew up in Tucson, but he traces his inspiration to meeting a farmer, Zephaniah Phiri Maseko, in the driest part of South Africa. Maseko operated a flourishing farm by carefully capturing and channeling the scant rain he received. “It was 100 percent real, what he was doing,” Lancaster remembers. He returned determined that the city he loved could flourish within the limitations of its climate.

An appreciation of the technologies and techniques used by native peoples to raise crops and live in the desert landscape is central to today’s water conservation movement. The Arnolds, who study ancient, historical, and contemporary water systems in the Southwest, regularly take students on extended field trips to study the earthen works at ancient pueblos. They also study ancient Roman, Middle Eastern, Mediterranean, and North African waterworks. “There’s an incredible history of water use to draw on,” says Peter Arnold.

Modern technology also will be essential. If the West is to survive what appears to be this once-in-a-millennium dry spell, it will be necessary to draw on a combination of ancient methods of water conservation as well as the latest research and innovations.

An example of the potential for building design to make a significant difference can be found at the University of Arizona in Tucson. An addition to the school’s architecture building was designed to capture rain from the roof and condensate from air conditioning units, storing it all in an 11,600-gallon tank integrated into the structure. The rooftop yields about 85,000 gallons annually, while the air conditioners provide even more, 95,000 gallons. An additional 45,000 gallons comes from water back-flushed from drinking fountains.

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California is currently in its third year of an “exceptional drought,” the worst category, which covers nearly the whole state.

The West as a whole is in the midst of a 15-year dry spell. The last time so much of Western North America was in a severe drought was between 1150 and 1160, nearly 900 years ago, according to Columbia University researchers.

The Drought Monitor website, a collaborative effort between the U.S. government and the National Drought Mitigation Center at the University of Nebraska–Lincoln, reports that more than 71 million Americans live in areas now suffering from severe, extreme, or exceptional drought. Drier than normal conditions are affecting large portions of 12 states across the Western U.S.

Much of the river water flowing through the West was captured behind dams and allocated between the states in the first quarter of the 20th century. The Colorado River, which provides water to people in seven states and Mexico, is particularly important. But an analysis of tree rings by researchers at the University of Arizona indicate the river’s flow early in the 20th century was substantially higher than the historic average, meaning the river full of water divided up nearly a century ago was liquid fool’s gold.

Climate change is also likely to mean sustained drier conditions with more periods of severe drought across the region, according to a review of climate change studies by Glen M. MacDonald, a professor of geography and the environment at the University of California, Los Angeles (UCLA). The research indicates “it is unlikely that the Southwest will see a return of any prolonged periods of moist conditions similar to the long wet spells experienced in the 20th century.”

That forecast, along with the drought, which already led to the imposition of widespread water conservation measures across California this summer, has opened more policymakers to options that represent a dramatic departure from the past, most significantly in Los Angeles.

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Just a little over a hundred years ago, the man who could with little exaggeration be considered the father of modern Los Angeles stood at the terminus of the just-opened Los Angeles Aqueduct, built to bring the city a plentiful supply of water from the Owens Valley in the Sierra Nevada mountains 220 miles distant. A crowd waited to see what William Mulholland, the larger-than-life-figure who had risen from ditch-cleaning to head the Los Angeles water department, would say.

That idea, that it was the role of government and others in positions of authority to make sure the water was there for the taking without further thought, as if from a magic fountain, was the guiding philosophy behind water management in the West for most of the 20th century. It helped to spur a Western boom that transformed the region in less than a century from semi-wild backwater to the place it is today.

With its success, it became a dogma the region’s boosters clung to long after the West’s major cities had grown to national significance. But recent years have brought a willingness to rethink what were once essential articles of faith: cheap water, no penalties for overdrawing aquifers, the preeminence of property rights, and local control.

Los Angeles provides the clearest example of the change. “All kinds of viewpoints that we’ve heard over the years were absolutely unbudgeable seem to be budging,” says Hadley Arnold. Mulholland’s city is now run by a mayor who is a supporter of water conservation efforts, and the city’s current head of water and power, Marcie Edwards—who, like Mulholland, started at the bottom as a clerk and worked her way to the top of the vast agency—has a very different view of the city’s relationship with water.

In an August interview with the Los Angeles Times, she acknowledged the city will likely have to raise water rates in the next year or so, stressed the importance of following conservation rules, and said she wants to reduce the city’s reliance on imported water by 50 percent by 2030 by capturing more stormwater, cleaning up contaminated groundwater, and reusing treated wastewater.

Just this month, California voters approved a proposition that would authorize $7.5 billion in bonds for a wide range of state water infrastructure improvements, including several approaches supported by water conservationists. “It’s a huge departure from the past,” says Peter Arnold.

Los Angeles has been in the forefront of recent initiatives, but other communities have also taken significant water conservation steps. In Tucson, Lancaster has worked with city officials and other advocates of water harvesting, including the non-profit Watershed Management Group, to implement changes in city policies. Tucson Water, the municipal utility, provides rebates for installing rainwater and greywater systems.

Four years ago, the city passed a water-harvesting ordinance for commercial property, the first in the nation, requiring that 50 percent of the landscaping water needs for new commercial sites be met by using rainwater captured from roofs and parking lots. The city has established “green street” standards that allow cuts in curbs and other changes to allow more water infiltration and less runoff. Watershed Management Group has worked with other cities in the state to develop similar initiatives.

Lancaster, who has published two popular guides for the public, Rainwater Harvesting for Drylands and Beyond:Volumes 1–2, speaks around the world on the practices he has learned and uses daily. He has worked with both private and government groups across the American Southwest and Mexico.

Yet he believes the most significant change has to come with the general public, a shift he has worked to bring about both through words and direct action. A recent heavy rainfall in Tucson found him soaking wet, out on his street, working with temporary makeshift barriers to channel the excessive street runoff into places where it could do the most good.

For years he has tried to get the Southwest to see the water it needs as best found in the heavens and not in the region’s dwindling aquifers and rivers. It once seemed like a quixotic quest, but as the West dries out, people are listening more attentively to people like the Arnolds and Lancaster. “It’s definitely changing,” he says, “slower than I’d like to see, but I am seeing a shift in attitudes. It’s there.”