Okay, first the bad news. In last week's New York Times Magazine, Jon Gertner pointed out that the planet's heating up, which means less snowpack in the Sierra Nevada and Rocky Mountain ranges, which means less water in the Colorado River, which means—that's right—catastrophe for the American Southwest:

Chu noted that even the most optimistic climate models for the second half of this century suggest that 30 to 70 percent of the snowpack will disappear. "There's a two-thirds chance there will be a disaster," Chu said, "and that's in the best scenario." ... A catastrophic reduction in the flow of the Colorado River—which mostly consists of snowmelt from the Rocky Mountains—has always served as a kind of thought experiment for water engineers, a risk situation from the outer edge of their practical imaginations.

Some 30 million people depend on that water. A greatly reduced river would wreak chaos in seven states: Colorado, Utah, Wyoming, New Mexico, Arizona, Nevada and California. An almost unfathomable legal morass might well result, with farmers suing the federal government; cities suing cities; states suing states; Indian nations suing state officials; and foreign nations (by treaty, Mexico has a small claim on the river) bringing international law to bear on the United States government.

In addition, a lesser Colorado River would almost certainly lead to a considerable amount of economic havoc, as the future water supplies for the West’s industries, agriculture and growing municipalities are threatened. As one prominent Western water official described the possible future to me, if some of the Southwest’s largest reservoirs empty out, the region would experience an apocalypse, "an Armageddon."

Still, what's missing from this picture? As Gertner notes in passing, it's farming, and not residential areas, that consumes the vast majority of water in the region (90 percent of Colorado's water goes toward agriculture). You'd think, then, that inefficient agriculture practices would get most of the scrutiny here. According to the U.S. Geological Survey, most irrigated farmland in the area—in California, Colorado, and Wyoming—is watered via flood irrigation, the least efficient method out there. Basically, farmers dig a bunch of trenches and dump water in them. In the short run, it's cheap and easy; in the long run, it tends to waste water and deplete topsoil.

Subsidies are part of the problem here: Large farms often qualify for taxpayer- subsidized irrigation water, paying as little as 10 percent of the full cost. That, in turn, discourages conservation: "A 1997 study by researchers at Cornell University suggests that more than 50 percent of irrigation water never reaches crops because of losses during pumping and transport." The subsidies also encourage farmers to grow water-guzzling crops like alfalfa, a crop that sucks up about 20 percent of California's water but comprises only a tiny part of the economy (it's mostly used to feed cows). I'd like to see more on the subject, but this seems like a major place to focus on, no?

P.S. And the Southwest isn't the only place suffering from dwindling water supplies. CJR has a rundown of the havoc caused by droughts in Georgia, Alabama, and Florida. (Plus the fact that no one's really been planning for any of this down there...)

--Bradford Plumer