This piece first appeared in Worldchanging.

It is likely to be a source of unhappiness for us that we have taken natural bounty for granted in designing our civilization. But it is likely to prove tragic that we have assumed not only the indestructibility of nature (heck, some fossils still argue that climate change is impossible because it is not within human abilities to wreck the climate), but also that the particularly beneficial circumstances of the 20th century are what is ecologically "normal." Nowhere is this more evident than in arid regions, and nowhere is it better studied than in the American Southwest.

There, in the deserts and mountains, we Americans have built huge cities, farms and ranches, and one of the world's leading tourism industries (think Vegas) predicated on the reliability of cheap, plentiful water. This was a mistake. Water in the very near future will be neither cheap nor plentiful, and much of the Southwest is destined for real trouble.

I have not read a clearer explanation of how much trouble the Southwest is in for, or a better accounting of the flawed thinking that got us into this mess, than James Lawrence Powell's excellent Dead Pool: Lake Powell, Global Warming, and the Future of Water in the West

Powell lays out, with devastating precision and a wealth of facts, the reality that the Southwest as we've known it over the last 50 years is already done for.
First, our assumptions about how wet the American West actually is have been based on a century that studies of tree rings show to have been anomalously wet: over the centuries, the region's usual state has been even drier than it is now.
Second, though climate change is expected to lead to more rainfall during wet years, in the West's four major river basins (the Columbia, Missouri, Rio Grande and Colorado), the number of hot years expected as climate change worsens will be several times the number of wet years.
Third, rising temperatures mean that the mountain snowpacks upon which all four rivers rely are going to continue shrinking. This is particularly a problem for the Colorado River basin, where evaporation into the desert air is so fast that "nearly 90 percent of the water in the streams must come from a virtual reservoir: the Rocky Mountain snowfields." But snow pack in the Rockies has already declined by 16 percent, and is expected to shrink far more, and far more quickly, in coming years.
Fourth, our other options for taking, storing and using water have run out. Aquifers are essentially fossil water, and are being depleted many, many times faster than they can refill. For our purposes, Western aquifers are non-renewable resources. New dams designed to catch winter and spring rain in wet years and store it for dry years are impractical in scale, financially and politically. There is, realistically, very little we can do to increase water supply, or even to keep it from disappearing rapidly.
How rapidly? Powell cites recent studies that with current water demand and even very minor climate change (which is not what we should expect now) there's a 50 percent chance that both Lake Powell and Lake Mead (the two largest reservoirs in the U.S.) will "reach dead pool" by 2021. That means so little water will be left in them that the water level falls below their dam's lowest outlets (and so no more water flows from them). As Powell notes, "A probability of 50 percent means that there is an equal chance that the reservoirs could fall to dead pool later -- or sooner." [his emphasis] The take away is that, unless profound changes are made, the desert Southwest will run out of water in the next couple decades.
"For the Colorado River basin and the Southwest," Powell says, "the threat from global warming lies not in the comfortably distant future -- the threat is here today. West of the 100th meridian, the danger derives not from the slow rise of the sea but from the more rapid fall of the reservoirs... business as usual cannot continue."
The changes needed are virtually unimaginable now. Powell shows that right now, farms in the region use 80 percent of the water, and cities use the rest -- about half of that for landscaping (which is why there are fountains in Phoenix and lawns in Las Vegas). Even cutting back agricultural use and slashing landscaping use and combining them with the most aggressive conservation efforts imaginable would still only at best buy time for a new way of life suited to a much drier, much hotter climate to emerge.
What that way of life looks like, Powell doesn't say, and I don't think anyone has even begun to imagine. The realities of living in places with high temperatures rivaling those today found only in Death Valley, where water is too scarce and too expensive to water lawns and fill swimming pools (and where higher energy prices make vast air conditioned spaces unrealistic); well, those realities are brutal. It will take some major innovation to imagine how to transform what's there now into a decent way of life in those conditions.
I expect that a lot of the desert Southwest will, in historical time, dry up and blow away. But for the foreseeable future, people will live there. If nothing else, there will be a certain percentage of the population that's just too impoverished or too old, too house-poor or too stubborn to leave. It's not too early to start imagining how to reinvent the future they're inheriting.

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