Dust on snow fuels rapid snowmelt

Strong dust loading onto the snowpack was a significant contributor to early melt out in the southern regions of the state including the San Juan Mountains.

Persistent high winds and dust-on-snow events fueled rapid snowmelt in the Gunnison Valley and across southwestern Colorado this spring — the snow melting away earlier than normal, even at high elevations. 

Gunnison Basin snowpack reached near normal peak snow water equivalent (SWE) this year, but peak runoff occurred almost three weeks early. Jeff Derry, the executive director of the Center for Snow and Avalanche Studies based in Silverton, said most SNOTEL monitoring stations in southwestern Colorado lost their snow early this spring. A lack of sizable spring storms, high winds and dust on snow created conditions that were ripe for rapid melting and the early disappearance of the snowpack. 

To illustrate the speedy decline, recent data collected by Aerial Snow Observatory flights revealed that, as of mid-June, the SWE of remaining snowpack in the Upper Gunnison Basin has fallen to 43,000 acre-feet, down from 119,000 in late April.

Once the melt started, it really kicked into high gear, Derry told the Upper Gunnison River Water Conservancy District late last month.  

At Slumgullion Pass, located just outside of Lake City, the average daily melt rate was 0.23 inches per day in April, the highest rate in at least 17 years. In 2006, it was only 0.01 inches per day. The story was similar up north at Schofield Pass above Crested Butte, an area that had received an impressive amount of snow accumulation during the winter, where snow melted out a week early. At the Upper Rio Grande SNOTEL station, dust on the snowpack’s surface and fewer spring storms caused the snowpack to lose almost 18 inches of water over a two-week period in April, almost triple the rate seen in 1992. 

Fresh snowfall creates a shiny white surface that reflects up to 90% of the sun back into space. When dust collects on snow it darkens the surface, causing the snow to absorb more solar radiation instead of reflecting it — warming the snow and melting the snowpack faster and earlier in the season. 

The Center for Snow and Avalanche Studies has been tracking dust on snow in Colorado since 2003. Derry told the Times the amount of dust varies from year to year, but research shows that dust events are becoming more and more common. 

In 2022, Derry tracked 11 dust storms that likely originated in the Four Corners region, the arid southwestern intersection of Colorado, Utah, Arizona and New Mexico. The Four Corners area is the source of most of the dust that travels into the state. The dust hits the San Juan Mountains first and the hardest and often dissipates in severity before it reaches the Gunnison Valley, he said. But this year there was plenty of dust to go around.  

March, April and May are typically the worst months for dust out of the southwest because of strong spring winds, Derry said. Numerous weather agencies, including the Colorado Climate Center and the National Weather Service, marked 2022 as one of the windiest springs on record — only adding to the problem. 

“When you see that severe dust, unless you get a really snowy springtime, you are going to see early melt,” Derry said.  

High winds alone can also contribute to early snowmelt. In addition to bringing in dust, dry, warm air masses can redistribute snow and kick it back up into the atmosphere where it sublimates — transitioning straight from a snow solid into a vapor. 

Warm temperatures, severe dust events and high winds are a bad combination, preventing the snow from sticking around, Derry said. The negative impacts from an early pulse of snowmelt can appear later in the summer with diminished stream flows compared to normal years. 

“The snowpack is a natural reservoir and if it's losing its water early that's going to create problems for almost everybody: recreation, fishers and farmers,” he said. 

Dave Gochis, hydro-meteorologist for the National Center of Atmospheric Research, has been tracking flows across Colorado. According to Gochis, early peak runoff was a widespread phenomenon, particularly throughout the southern half of the state. The Dolores, Animas, Rio Grande, Conejos, Uncompahgre, Gunnison and Taylor rivers all peaked in mid-May, nearly a month earlier than normal, depending on the basin.  

As of June 9, the streamflow gauge on the Gunnison River read 74% of the historical average. On Tomichi Creek, streamflow sits about 22% of average. Upstream, the East River at Almont and the Taylor River at Taylor Park measured over 80%.

Local rafting guide Vito Covelli said that, although early runoff can negatively affect fish and the health of the river, he doesn’t expect it to slow tourism along the Taylor River. The brunt of Three Rivers’ rafting business spans eight weeks from June 22 to August 15 when kids go back to school, far after peak runoff. Flows also remain steady because water is released out of the dam. 

“I've already had better trips this year so far than I've had the last two years in terms of excitement and water levels,” Covelli said. “I think that's going to be pretty consistent, at least till the end of July and it'll get us through our tourist season.”

(Bella Biondini can be contacted at 970.641.1414 or bella@gunnisontimes.com.)