In a city running out of water, massive housing projects rise in clouds of dust on the outer reaches of the Las Vegas Valley like stucco ramparts built by some demented desert king. Just over the hills to the east, Lake Mead, which is on the Colorado River, the area's main water source, is literally drying up. Runaway population growth and a historic drought have rendered the nation's largest reservoir a virtual drainage ditch, down to a skeletal 48 percent of capacity. Yet construction in Las Vegas continues unabated. The city's latest megaproject is a master-planned "sustainable community" of 16,000 homes—anchored by a high-rise "neighborhood" casino—to be built about 15 miles northwest of the Las Vegas Strip, at the gateway to beloved Mount Charleston, part of the region's only national forest.

The method to this head-in-the-sand madness has its roots in faraway Washington, D.C., in a plan quietly aided by Senate Majority Leader Harry Reid. (View slideshow.) In 2004, with the water level at Lake Mead plummeting and panic setting in that Las Vegas might actually need to curtail its blistering growth, Nevada's senior senator helped to push through a reprieve. He co-sponsored a law granting the Southern Nevada Water Authority a free right-of-way on federal land to pipe groundwater into Las Vegas from central Nevada, hundreds of miles away. The $3 billion plumbing plan would tap the Great Basin aquifer, a vast underground sink that runs from Death Valley, in California, across central Nevada and into western Utah. Think Muammar Qaddafi and his Great Man-Made River Project in the Libyan Sahara, or Roman Polanski's Chinatown, the 1974 film based on what happened when a similarly thirsty Los Angeles turned California's Owens Valley into a dust bowl a century ago. As the Great Basin's groundwater is drained, desert springs and seeps will dry up, endemic plants and wildlife will die off, and farms and ranches will wither away, according to several scientists who have studied the plan. Eventually, the aquifer, which took millennia to fill, will run out, like other Nevada mother lodes mined into oblivion. What then for Las Vegas, whose civic boosters won't accept that the driest desert in North America isn't the best place for another million people in addition to the nearly 2 million already there?

Reid, the enabler, is actually a darling of environmentalists on the East and West Coasts. In 2005, the influential League of Conservation Voters gave him a perfect score for his voting record on environmental issues in the Senate (though his score dipped in 2006), and he is roundly praised by the national Sierra Club for his opposition to a laundry list of things it is against, among them coal-fired power plants and oil drilling in Alaska's Arctic National Wildlife Refuge. Yet the national Sierra Club and other major environmental groups made nary a peep when the bill enabling the pipeline passed or when Reid co-sponsored legislation to sell off large chunks of government land in the Las Vegas Valley to developers intent on extending metropolitan sprawl. Reid's relationship with the national Sierra Club is so harmonious that he even briefed Carl Pope, the group's executive director and one of Reid's friends, on the pipeline gambit. Pope says the senator's heads-up was just a courtesy. "He said, 'Look, it's important to me that we deal with our water supply problems in Clark County. This appears to be the best way,' " Pope recalls. "That's the level at which we discussed it." The Sierra Club focuses on broad issues such as climate change and generally doesn't make regional water disputes a high priority. And it certainly doesn't give Reid any sort of "pass," Pope adds.