U.S. Water News Online
PHOENIX -- A new study suggests that a decade of higher temperatures and shrinking runoff seasons have contributed to the drought that has crippled Colorado River reservoirs.
The study found warmer temperatures in the West's highest elevations could reduce winter runoff into the river, a major water source for Arizona, by as much as 30 percent over the next 50 years.
Even a subtle shift in climate could further weaken a river already overburdened by growing cities and could lead to chronic water shortages, especially in Arizona, according to the study.
"This climate disruption is already under way," said Stephen Saunders, president of the Rocky Mountain Climate Organization, a Louisville, Colo., group that produced the study.
He said the evidence is clear that climate change "will lead to more heat, less snow, less water when we need it, and possibly more drought."
Runoff from mountain snow is the weak link in the West's water supply. It provides as much as 70 percent of the region's water, including as much as two-thirds of the water used in Arizona's largest cities.
But warmer weather can result in less snow, which directly reduces the water supply, or it can melt the snow too early. When that happens, reservoirs can't store it all, and some of the runoff will be lost.
"We're getting warmer at exactly the time of year that snow needs to store water," said Brad Johnson of Arizona Public Interest Research Group, which released the climate study. "It's a real threat to our water supply that we should take seriously and address."
The study urges stronger efforts by the state and federal governments to reduce so-called greenhouse gases, such as carbon dioxide, which are produced by combustion of fossil fuels. Many scientists believe greenhouse gases and other man-made pollutants have accelerated global warming trends.
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