Sin City's Greatest Sin?

In his tour of the thirsty West, Eric Holthaus stops in Vegas, and nearby Lake Mead, Sin City's main water source:

Lake Mead provides 90 percent of the water to the once-again booming city of Las Vegas, as well as indirectly to Phoenix, Tucson, Los Angeles, and agricultural areas downstream via diversions from the Colorado River. As the result of an ongoing multiyear drought, this giant lake is now approaching the lowest water levels since its construction.
When we saw it for the first time, we gasped.
The sight of so much water in the middle of a desert is in itself brain-twisting, but to see the bright-white “bathtub ring” marking the lake’s historic high-water mark more than 100 feet above current levels, contrasted with boats merrily speeding around on the dwindling reservoir, was nearly too much to take. It was a sharp reminder that despite building dams, aqueducts, and other super-human feats, water in the desert is inherently temporary. We stayed only a few minutes.
The last time water levels were this low, in 2010, federal officials contemplated worst-case scenarios of forced cuts to Las Vegas—of both electricity and water. It didn’t happen then, but the drought this time around is worse.
The lake is now expected to reach a new record low of 1,080 feet by April 2015 and to cross the first trigger for downstream water cutbacks at 1,075 feet shortly thereafter. By summer 2015, the water supply to Las Vegas itself could be affected if an $817 million tunnel project—currently months behind schedule—isn’t yet completed. That project, conceived as a way to extend Lake Mead’s usefulness in the face of climate change, is designed to suck water from the lake all the way to the very bottom—a point long after even the turbines of Hoover Dam would have to shut down, possibly for good.
The new tunnel can’t be finished fast enough. As the magnitude of the current drought started to hit home, construction of an impromptu tunnel designed to buy the larger project a few months of time was approved late last year. Officials described the newest tunneling project as an “emergency meant to avoid an emergency.”

It all has the feel of a patient on life support, with a spaghetti of IV lines coming out of both arms. The morbidly curious can follow the daily level of Lake Mead (down another 1.7 inches Monday), via the U.S. Bureau of Reclamation website. Holthaus goes on to say that Las Vegas has very high water consumption per person.  I would be curious to know how much of that high consumption is used to irrigate golf courses, how much is used in the massive casino fountains, how much goes to watering residents' lawns and how much just gets used by the huge numbers of tourists.  Probably the vast majority goes to the first three, but the last one has to contribe a decent amount to that per capita use rate.  Whatever the split, millions of people living in the desert is a really terrible idea that we'll pay for in the future.