Despite This Year's Bumper Snow Crop, 30-Year Snowpack Decline In Rockies Worst In Centuries

(Reuters) - Snowpack declines in the Rocky Mountains over the last 30 years are more significant than during any other period in past centuries and foreshadow a strain on summer water supplies for more than 70 million people across the Western United States, a U.S. government study said.

Despite this year's record snowpacks in the Rockies and resulting floods, declines over the three decades have shown a an unusual pattern compared to reconstructions of snowpacks going back 1,000 years, according to the Geological Survey study released on Thursday, in the journal Science.

Runoff from winter snowpack, layers of snow that build up in mountains, accounts for 60 to 80 percent of the West's annual water supply, the study said.

The declines can be attributed to unusual springtime warming caused by man-made climate change and come during the summer, which is the period of highest demand for water in the West, it said. "The more we increase temperature, the earlier we melt out our snow pack and the less of it there is to get though our warm dry summers," said USGS scientist Gregory Pederson, the lead author of the study.

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http://www.reuters.com/article/2011/06/09/us-usa-snowpack-melt-idUSTRE7587B820110609