You’ll find Fishman’s book in the nature section at Barnes & Noble, but it’s really about urban planning. Because the creeping hydro-crisis has nothing to do with “running out of water.” The earth has the same amount of water as it had 4 billion years ago, and it always will. “It’s all Tyrannosaurus rex pee,” says Fishman with a laugh. The water’s recycled endlessly through the clouds, but it’s the way we’ve built that’s made it seem scarce — with industry, farming and cities in places where there’s not enough water to support them, but still demanding more every year.

Luckily, an urban-planning problem can be mitigated with urban-planning solutions, and cities are blazing the trail — including, believe it or not, Sin City itself. Today, Vegas is soaked in “reclaimed water,” water that’s been used once and then purified for another go-round. It waters the golf courses and washes the thousands of hotel bed sheets. Even the pond at Treasure Island, where the nightly pirate-ship battles take place, is filled with water that the hotel’s guests have brushed their teeth with. (It gets run through a treatment plant under the casino.)

But even reclaimed water has a way of vanishing in a place where the sun shines 300 days a year — some estimates suggest Lake Mead loses half its water to evaporation. One solution? Store it underground, says Tom Brikowski, professor of hydrology at the University of Texas-Dallas. “It could work in a lot of places and it’s starting to be done now.” For instance, Tampa, Fla., is trying it out with a method called aquifer storage and recovery, pumping water into the earth when it rains, then extracting it during the drier months.

It’s an artificial version of how Los Angeles’ water supply operates naturally. California gets nearly all its precipitation in the winter, much of it as snow in the eastern Sierras. As the snow slowly melts through the summer, it becomes part of the state’s water supply — nearly 5 trillion gallons trickling toward Los Angeles, San Diego and other Southern California cities. Climate change is wreaking havoc on this system. “We depend on that water staying up in the mountains as snow through August,” says Andrew Schwartz, an engineer for the state’s Department of Water Resources. “Now, a lot of the precipitation that used to fall as snow is falling as rain, and the stuff that still falls as snow is melting faster.”

Making things worse, on its way south, this water flows through the Sacramento-San Joaquin Delta. The rising sea levels are turning the delta saltier, rendering some of the water undrinkable. It’s a one-two punch that California may try to fight with what Schwartz says would be “the biggest construction project in the country,” an enormous water tunnel that would bypass the delta and head to cities in the southern part of the state.

Such a project would cost billions. Changing a city’s culture is far cheaper, and while California is reasonably water conscious, in San Antonio, conserving water is a religion. In the ’90s, the city was sued by the Sierra Club for draining the Edwards Aquifer. The aquifer happens to be the home of the Texas blind salamander, an endangered amphibian. A small culture war ensued, but after a few years of predictable hippies-versus-cowboys animus, something incredible happened: San Antonio became a capital of conservation chic. Low-flush toilets became status symbols, and overwatering your lawn could get a person ostracized. Water consumption dropped from 200 to 130 gallons per person per day. And suddenly, droughts that crippled neighboring cities weren’t affecting San Antonians. “I hate to say ‘big government,’” says Brikowski, “but these regional plans where everyone shares the sacrifice are pretty effective.”

Compare that to Brikowski’s hometown of Dallas, the “water hog” of Texas, where no such stigma exists, and the average resident uses more than twice as much water as a San Antonian. Between 1980 and 1999, as other big Texas cities slashed their water consumption, Dallas’ grew by 35 percent. And now Dallas, like Vegas, is looking for water elsewhere — specifically, east Texas and Oklahoma. “It’s not that they need the water to survive,” one irate east Texan told the Wall Street Journal. “What they want is to destroy our wildlife so they’ll have enough water for their grass.”

The kicker is this: Dallas isn’t even that parched. It typically gets only a few inches less rain than Boston each year, and even during last year’s epic drought, it still got 26 inches. Likewise, Florida. The so-called Sunshine State gets tons of rain yet suffers from water shortages, says Fishman, simply because they don’t bother to use it. “Forty-eight inches of water fall as rain on every square foot of Florida. They gather it, put it in a drain, and ship it right out to the ocean. And then they take their water supply from an aquifer under the state, and that aquifer is tapped.”

In other words, it’s not the water that’s bad, it’s the system. “The system is set up to dispose of storm water, and then there’s a vast, separate infrastructure that depends on groundwater,” says Fishman. Unifying these systems — drinking water, wastewater and storm water — could transform a city from one with chronic water shortages to an oasis of hydration.

There’s nothing icky about it. Dallas’ wastewater is so fit for reuse that another city drinks it — Houston, 250 miles down the Trinity River, where Dallas dumps its wastewater. People grimace at the phrase “toilet-to-tap,” a water-treatment option that’s spawned many a gross-out news story. But lots of us drink such water already. “The water in Houston has been through Dallas toilets,” Brikowski says bluntly.

If rivers like the Trinity can move water from city to city, why can’t we? Could waterlogged Baton Rouge send its overflow to Oklahoma City? Believe it or not, the idea has been floated. Patricia Mulroy, Las Vegas’ celebrated water czar, wants the U.S. to construct transnational canals to transport water from the Mississippi Valley to the dusty Midwest.

Fishman sees a more realistic scenario in which “places like Chicago start using their water supplies to woo companies.” Companies like Intel, whose water-guzzling microchip plants sit near bone-dry Phoenix. This could could have all sorts of implications for where economic growth occurs in the future — shifting, for instance, the balance of prosperity from the Sun Belt back to the Rust Belt. And it might not be too far off. Because while the average person may not think much about the future of water, says Fishman, “these huge corporations have water security on their top-five lists of critical issues.”

Till then, small changes can make a big difference. Fishman recalls how, in the 1950s, Hong Kong, just beginning to industrialize, mandated that its toilets be flushed with seawater. Today, the city’s population has quadrupled, and 80 percent of its toilets still work that way. Because of one forward-thinking tweak, today Hong Kong saves 73 billion gallons of water a year. “That would supply a city of 2 million,” says Fishman — the population of Las Vegas, it just so happens. “It’s a perfect example of how organization can have a huge impact on outcome.”