Many places in the world are getting drier-not just becuse of climate change but also because of the demands of irrigation and industry. Lak Chad has shrunk to one-twentieth of its size in 1960. The Aral Sea is about gone. The Colorado river no longer reaches the sea in the dry season. Just 10 percent of Mesopotamian marshlands are left. Worldwide, some 2-3 billion people could face acute freshwater shortages by 2020.