More drought predictions in America's southwest

erin poster A new report from the University of Arizona (UA), via TerraDaily (among others), suggests that the American Southwest could be on the cusp of a drought that is predicted to be the worst since the 12th century.  

The UA team, led by Connie Woodhouse, an associate professor of UA’s School of Geography and Development, published their results in the early edition of the Dec. 14 issue of PNAS – the Proceedings of the National Academy of Sciences. The name of the report is “A 1,200-year perspective of 21st century drought in the southwestern North America.” 

In the 11th, 12th and 13th centuries, according to tree ring studies conducted jointly by the U.S. Geological Survey (USGS), U.S. Bureau of Reclamation, and several universities and relevant organizations, massive droughts destroyed the Anasazi, Fremont, Lovelock and Mississippian (Cahokian) mound builders who inhabited the central U.S. from Red Wing, Minnesota to Key Marco, Florida.  

That is, by 1150 AD, both the Anasazi and Frement cultures were under severe stress, so that 150 years later both had collapsed, in spite of their vast extent, and survivors had either fled to more hospitable climes (Fremont) or disappeared (Anasazi).  

These droughts extended as far as the Pacific coast in California, and were apparently produced by a “minima” (cold, or weak) phase of the Pacific Decadal Oscillation colliding with a “maxima” (warm, or strong) phase of the Atlantic Multi-decadal Oscillation.  

Both are oceanic cycles that largely determine atmospheric patterns. For a superb explanation of their actions, please read Robert Stewart’s definitive work. Oceanic cycles are now known to drive atmospheric circulation and trigger the amount of moisture that reaches landmasses. So the study by UA is doubly relevant, not just to drought but to global warming, a larger pattern of massive weather influences.  

Using data gathered from the past 1,200 years, UA researchers have projected future climate models that suggest the American Southwest is in for a world of hurt, in terms of cities’ abilities to provide their citizens with drinking water and household water, let alone enough extra to water lawns, ornamental plants, gardens and crops.  

This dearth of water for crops is, in fact, what drove agriculture out of California’s Carrizo Plain, to be replaced (hopefully) by solar panels. And it’s not merely a lack of water, but the fact that reduced water supplies tend to force the soil to accumulate salts, which are contraproductive to most food crops. 

UA researchers are hesitant to say that these modern droughts will be worse than historical ones, but emphasize that – were droughts to occur on a similar scale – the higher temperatures implied by global warming would likely exacerbate their effect.

One of the measurements the researchers used was Colorado River flow and height. In the 12th century, scientists have extrapolated that river flowed about 15 percent below normal.  

Sampling over the past decade shows the river at its lowest point since hydrologists started keeping a log in 1906. And an Oct. 21 report indicates that Lake Mead, the Colorado River’s major reservoir, is as low as it’s been since 1937, when it was first being filled after the completion of Hoover Dam.  

In fact, a 2009 report suggests that, by 2057, there is an even chance that all the Colorado River reservoirs (located in Arizona, California, Nevada and Utah) will run completely dry.   

On the flip side of this dire report, consider the fact that drinking water in 31 cities has been found to contain hexavalent chromium, a known carcinogen. The report, by usually reputable national public interest organization Environmental Working Group, or EWG, suggests that this chemical – which moviegoers will readily associate with environmental advocate Erin Brockovich – exceeds California public health-recommended levels in at least 25 of the 35 cities surveyed.  

Not only did chromium-6 (the hexavalent variety) comprise more than half the chromium found in tap water, but the greatest density was found in water utilities using groundwater (rather than surface water) for their supply, additionally raising the risk of regional lung cancer clusters.  

For those over 50 reading this report, did you ever think you would live to see the day when the water you need to live was either absent or lethal?

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  • Posted on Dec. 22, 2010. Listed in:

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