Wednesday, July 22, 2009
Colorado River Reservoirs Could Bottom Out
All reservoirs along the Colorado River might dry up by mid-century as the West warms, a new study finds. The probability of such a severe shortage by then runs as high as one-in-two, unless current water-management practices change, the researchers report.
The study's coauthors looked at the effects of a range of reductions in Colorado River stream flow on future reservoir levels and at the implications of different management strategies.
Even under the harshest drying caused by climate change, the large storage capacity of reservoirs on the Colorado might help sustain water supply for a few decades. However, new water management approaches are critical to minimize the chances of fully depleting reservoir storage by mid-century.
"This study, along with others that predict future flow reductions in the Colorado River Basin, suggests that water managers should begin to re-think current water management practices during the next few years, before the more serious effects of climate change appear," says lead study author Balaji Rajagopalan of the University of Colorado in Boulder (CU-Boulder).
The findings by Rajagopalan and his colleagues have been accepted by the journal Water Resources Research, published by the American Geophysical Union (AGU).
The Colorado River system is enduring its 10th year of a drought. Fortunately, the river system entered the drought in 2000, with the reservoirs at approximately 95 percent of capacity. The reservoir system is currently at 59 percent of capacity, about the same as this time last year, says Rajagopalan. Roughly 30 million people depend on the Colorado River for drinking and irrigation water.
The research team examined the future vulnerability of the system to water supply variability coupled with projected changes in water demand. They found that through 2026, the risk of fully depleting reservoir storage in any given year remains below 10 percent under any scenario of climate fluctuation or management alternative. During this period, the reservoir storage could even recover from its current low level, according to the researchers.
But if climate change results in a 10 percent reduction in the Colorado River's average stream flow as some recent studies predict, the chances of fully depleting reservoir storage will exceed 25 percent by 2057, according to the study. If climate change results in a 20 percent flow reduction, the chances of fully depleting reservoir storage will exceed one in two by 2057, Rajagopalan says.
"On average, drying caused by climate change would increase the risk of fully depleting reservoir storage by nearly ten times more than the risk we expect from population pressures alone," Rajagopalan says.
"By mid-century this risk translates into a 50 percent chance in any given year of empty reservoirs, an enormous risk and huge water management challenge," he says.
The river hosts more than a dozen dams along its 2,330-kilometer (1,450-mile) journey from Colorado's Rocky Mountains to the Gulf of California.
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St. Thomas which was a city covered by Lake Mead due to Hoover Dam construction is now exposed due to recession of water levels. To some that may seem like justice because of what was done to St. Thomas originally because of the dam construction, but now this lake which is one of the largest has millions of people dependent on it for water. So now, those in this area who once lost all due to the water coming in may well see that again because of the opposite effect. This is a stark example of what population increases and climate change combined with waste can lead to. It should be a lesson to us all.
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