How it Could Happen

Rising temperatures in the West have reduced high-altitude winter snowpack, which accounts for 80 percent of the region’s fresh water. Tree ring data, meanwhile, suggests the area is prone to epic water shortages, such as the six-decade megadrought from 1118 to 1179. While most scientists maintain that conservation and better water management could stopgap any shortages, “nobody has a crystal ball,” says Peter Gleick, Ph.D., president of the Pacific Institute. “I think climate change is going to make water availability worse, not better. It’s going to be hotter and drier, with more political conflict over resources.”