Las Vegas is a city that shouldn't be — but somehow is. The desert metropolis of nearly 2 million people survives thanks only to the intricate system of irrigation and reservoirs that tap the flow of the Colorado River. Much of the water is kept in the artificial Lake Mead, 30 miles south of Las Vegas. But Lake Mead could be slowly drying up. The region is in the grips of a back-breaking 11-year drought, and in October the reservoir fell to its lowest level since it was filled nearly 75 years ago. If it keeps falling, an official shortage will be declared, and the water level could impact hydroelectric production from the nearby Hoover Dam. But this is just a symptom of a larger threat to the future of the West. The combination of climate change — likely to result in warmer and drier weather — continued agriculture and population growth in the West is straining water supplies. Eventually, something will have to give.