Justin Sullivan/Getty Images toggle caption Justin Sullivan/Getty Images Hotter temperatures are leading to emptier reservoirs across the West, like Lake Oroville in Northern California. Justin Sullivan/Getty Images By almost every measure, the drought in the Western U.S. is already one for the record books. Almost half the country's population is facing dry conditions. Soils are parched. Mountain snowpacks produce less water. Wildfire risk is already extreme. The nation's largest reservoir, Lake Mead, is headed to its lowest level since it was first filled in the 1930s. The past year has been the driest or second driest in most Southwestern states since record keeping began in 1895. Farms and cities have begun imposing water restrictions, but Western states are facing a threat that goes deeper than a single bad year. The hotter climate is shrinking water supplies, no matter what the weather brings.