Unabated Global Warming Threatens West's Snowpack, Water Supply

New study shows a snowline creeping higher in the Rockies, Sierra Nevada and Cascades and the resulting decrease in spring runoff endangers those below.

Low-elevation snowpack across the Rocky Mountains, the Sierra Nevada and the Cascades will disappear in the coming decades if global warming continues unabated, according to a new study.  The changes will cause water shortages in the region and dry out forests and grasslands, the study's authors say.

According to the research, the snow line—the altitude above which it snows, and below which it rains—will climb as much as 800 feet in the Colorado Rockies, and 1,400 feet in the Rockies of Idaho and Wyoming by 2100 if greenhouse gas emissions continue at the current rate.  The snow line will rise by an average of 950 feet across six Western mountain regions by century's end.  The study, by a team of University of Utah scientists, was published online in the journal Geophysical Research Letters last month.

A shift of that magnitude means less spring runoff for millions of square miles of watersheds in the lower elevations of the West.  The melting of the spring snowpack determines how much water feeds critical reservoirs in 11 Western states.  That water helps sustain Phoenix, Los Angeles, Las Vegas and other cities, as well as farms and mountain ecosystems, through hot, dry summers.

Less spring snowpack means water managers will have to capture runoff earlier in the season, and dried up forests, brush and grasslands will increase early season wildfires.  Western ski resorts will also be affected, because the snowline will rise above the base elevation of many of them, according to the study.

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