Thursday, December 8, 2011

Climate Change And The American Southwest

William DeBuys at TomDispatch, via nc links:
The simple rule of thumb for climate change is that wet places will get wetter and dry places drier. One reason the dry places will dry is that higher temperatures mean more evaporation. In other words, there will be ever less water in the rivers that keep the region’s cities (and much else) alive. Modeling already suggests that by mid-century surface stream-flow will decline by 10% to 30%.
Independent studies at the Scripps Oceanographic Institute in California and the University of Colorado evaluated the viability of Lake Mead and eventually arrived at similar conclusions: after about 2026, the risk of “failure” at Lake Mead, according to a member of the Colorado group, “just skyrockets.” Failure in this context would mean water levels lower than the dam’s lowest intake, no water heading downstream, and the lake becoming a “dead pool.”
If -- perhaps “when” is the more appropriate word -- that happens, California’s Colorado River Aqueduct, which supplies water to Los Angeles, San Diego, and the All-American Canal, which sustains the Imperial and Coachella Valleys, will go just as dry as the Central Arizona Project aqueduct. Meanwhile, if climate change is affecting the Colorado River’s watershed that harshly, it will undoubtedly also be hitting the Sierra Nevada mountain range.
The aptly named Lester Snow, a recent director of California’s Department of Water Resources, understood this. His future water planning assumed a 40% decline in runoff from the Sierras, which feeds the California Aqueduct. None of his contemplated scenarios were happy ones. The Colorado River Aqueduct and the California Aqueduct make the urban conglomerations of southern California possible. If both fail at once, the result will be, as promised, the greatest water crisis in the history of civilization.
If we get a repeat of last year's La Nina, that'll be good for Lake Mead, but very, very bad for Texas.  Anyway, long-term, things look pretty bad for the Sunbelt.  I'll take my winters, thank you very much.

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