'Megadrought' Could Come to Southwest: Study 3-decade dry spell could spark mass migration: experts By Matt Cantor, Newser User Posted Aug 31, 2014 4:21 PM CDT 86 comments Comments This Oct. 22, 2010 file photo, shows low water levels in Boulder Harbor in Lake Mead, Ariz. (AP Photo/The Arizona Republic, Mark Henle, file) (Newser) – An "extreme" drought is already affecting 82% of California, researchers say, and 58% is facing an even worse "exceptional" drought—but perhaps the most worrying news deals with the possibility of a 30-year "megadrought." The odds of that occurring now range from 20% to 50% in the next 100 years, a Cornell University study finds. Such droughts may be "worse than anything seen during the last 2,000 years," experts say, per the Los Angeles Times. "As we add greenhouse gases into the atmosphere … we are weighting the dice for megadrought," a researcher notes. And that could lead to migration that's never before been seen in the US, the Cornell Chronicle notes. Far higher is the risk of a 10-year drought, one comparable to what was seen during the Dust Bowl, the Times reports. The chances of that are 80%, and researchers point out that such lengthy dry spells occur about "once or twice per century." New Mexico and Arizona are also likely victims of extended drought, though there's some good news for Idaho, Montana, and Washington, whose risk of such a fate may shrink, experts say.