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An analysis of more than 50 years of records at the U.S. Department of Agriculture's (USDA) premier mountain observatory in Idaho shows that climate warming is causing the rain/snow transition elevation to move upslope.
During the past five decades, mean temperatures have risen 4 to 5 degrees Fahrenheit, according to an Agricultural Research Service (ARS) analysis of data from the Reynolds Creek Experimental Watershed (RCEW) near Boise, Idaho. This warming has occurred across a range of elevations. ARS is USDA's principal intramural scientific research agency, and this research supports the USDA commitment to responding to climate change.
The higher temperatures have caused a shift from snow to rain, with the most profound changes at lower elevations, which saw a shift from 44 percent snow to 20 percent.
A system once dominated by winter snowfall now experiences a mix of rain and snow, with more streamflow in winter and less in spring. This means there is less water for ecosystems and agriculture during the spring and summer growing seasons. These changes make forecasting and managing western water resources more difficult and present a serious challenge to agriculture in the region.
Danny Marks, a hydrologist who specializes in snow and cold season hydrology of mountain regions, directed this analysis, working with soil scientist Mark Seyfried and colleagues. Both Marks and Seyfried are at the ARS Northwest Watershed Research Center (NWRC) in Boise, which manages the RCEW in the Owyhee Mountains. These mountains are part of the Great Basin of the intermountain western United States. The mid- and low-elevation snow measurement sites show more than a 60 percent reduction in peak snow water content, and the peak now occurs a month or more earlier.
Most of the snow measurement sites across the western United States are high-elevation measurement sites that can't detect the strong trends shown in this latest analysis of the RCEW at mid-to-low elevations.
Read more about this research in the January 2011 issue of Agricultural Research magazine, available online at: http://www.ars.usda.gov/is/AR/archive/jan11/global0111.htm.