Snowpack in Rockies Declines From Warmer Temperatures, U.S. Says

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http://www.bloomberg.com/news/2011-06-09/snowpack-in-rockies-declines-from-warmer-temperatures-u-s-says.html

Snowpack in the Rocky Mountains has been decreasing for five years because of hotter temperatures, a study tracking 800 years of data indicated, suggesting water supplies in the Western U.S. may be reduced.

The U.S. Geological Survey in Montana used a network of 66 tree-ring chronologies to determine that layers of snow formed in cold areas in the region decreased in the late 20th century more than any other period since 1200, according to a study published today in the journal Science.

Snowpack in both the northern and southern sections of the Rockies are now declining at the same time, which may mean that higher temperatures and not shifting precipitation rates may be causing the change, the researchers said. Through the 1980s, levels rose and fell in each area.

Runoff from the snow in the Rockies feeds the Colorado, Columbia and Missouri rivers, the primary water sources of more than 70 million people, the study said. That melting snow accounts for 60 percent to 80 percent of the water supply in those areas.