Buried dust layer could influence runoff in Aspen area
A thin layer of dust that a windstorm deposited on the Aspen area Sunday evening may play a key role in how the snowpack melts this spring and early summer, according to Chris Landry, executive director of the Center for Snow and Avalanche Studies in Silverton.
High winds blowing the dry sands of the Southwest and the Colorado Plateau slammed into the Colorado mountains late Sunday afternoon and into the evening. There was so much dust in the air, blowing through in plumes, that the sky turned an odd orange-ish hue before sunset.
“It was a significant event,” Landry said. The nonprofit center runs the Colorado Dust-on-Snow Program, which monitors “dust events,” measures how much dust gets deposited in the snowpack and assesses how it will affect the spring runoff.
Landry was in the field Sunday visiting 11 sites in Colorado, including McClure Pass in the Crystal River Valley, where the program monitors snowpack and assesses dust. He and a colleague stayed in Steamboat Springs on Sunday night and weren’t sure initially how extensive the dust incident was because fresh snow fell overnight at the resort. It became more apparent, by the time they reached Interstate 70, that dust had coated the snowpack, and it was “dead obvious” by the time they reached the Roaring Fork Valley that it was significant, Landry said.
It affected the mountains as far east as Loveland and extended into the Grand Mesa to the west and Red Mountain Pass and the surrounding San Juans to the south. The Dust-on-Snow Program still is assessing how far north the dust spread.
“This was a huge event. It might have got most of the mountains,” Landry said.
Although it covered a widespread geographic area, it didn’t leave a layer of dust as thick as windstorms did at some locations in the Colorado mountains last spring, Landry said. His staff will collect snowpack samples in June, where all layers have merged, to assess the dust’s potential impact on runoff. The dust leaves a distinctive layer in the snow sample.
Most dust storms occur in March, April and May, so the prospects are high that more will roll through the mountains, according to Landry.
“We’re now entering the thick of it,” he said.
Sunday’s storm was the fourth incident to deposit dust in at least a portion of the mountains. Two earlier events left smaller amounts of dust in the Aspen-area snowpack, he said.
While he deemed Sunday’s event significant, it wasn’t on the same level as dust storms that affected many parts of Colorado last year, according to Landry. Nevertheless, the event likely will have consequences.
“There is now sufficient dust in these snowpacks,” Landry said. There’s no question Sunday’s dust will “influence snowmelt runoff,” he said. The issue is how much.
Skiers reported ochre-colored dust and mud on the slopes of Aspen Mountain and other local ski areas on Monday. Fresh snow Tuesday covered that layer, and more snow fell Wednesday. When the snow melts, the dust layer will re-emerge, Landry said. The darker dust absorbs the sun and melts the surrounding snowpack more quickly than when there is no dust, he said. A short and intense runoff can cause problems ranging from flooding to reduced irrigating. It also can affect whitewater rafting, an important part of the mountain economy in the summer.
The accelerated melting caused by dark dust layers is exacerbated by sunny, warm conditions.
“Weather still really matters on how this dust will play out,” Landry said.
More information on the Colorado Dust-on-Snow Program is available at http://www.codos.org/#codos.
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