Snowpack in Colorado, across the West is melting earlier than it did in the 20th century |

Snowpack in Colorado, across the West is melting earlier than it did in the 20th century

When researchers analyzed decades of snowpack monitoring data across western North America, including many in Colorado, they found that snow at more than a third of the stations melted significantly earlier in the year than it did in the mid- to late-20th century.

The new study from the University of Colorado is the first of its kind to look at historical snowmelt data to understand the long-term impacts of a warming world on alpine snowpack, the water storage of the West.

Colorado’s snowpack acts like a drip irrigation system, with the snowpack — and thus water stored as snow — peaking around April 1 each year. As spring brings warming temperatures, snow slowly and steadily melts, first saturating the dry ground, then flowing through rivers and streams to both human and ecological uses.

If the snowmelt begins to drip earlier in the season, there is less runoff to flow on and through the ground during the summer months. Unless precipitation increases — either adding to the snowpack in the winter, or supplementing runoff in the spring and summer — there are fewer water resources during the growing season.

Snowpack declined about 11% during the study period, but earlier winter runoff was roughly three times as widespread, based on data from 1,065 snow telemetry sites. Measures like snowpack can inform resource managers of the current water year’s conditions, Musselman said, while runoff timing is likely more indicative of long-term climatic trends.

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