Dust on snow event this week may affect runoff

Dust streaming across Four Corners April 29, 2009 via MODIS
Dust streaming across Four Corners April 29, 2009 via MODIS

From The Aspen Times (Scott Condon):

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.

From the Summit Daily News (Alli Langley):

The dust storm that blew through Summit County earlier this week could have serious consequences for skiers, water managers and farmers…

Depending on weather conditions in the coming weeks, the dust could cause the snow to warm and freeze in thicker layers, increasing the risk of avalanches, said Spencer Logan, avalanche forecaster with the Colorado Avalanche Information Center.

In 2006, dust storms in February contributed to a heavy-avalanche season, he said, with more than 100 slides in May that year. In 2012, though, the area experienced heavy dust but few avalanches…

Another smaller dust storm Tuesday, which probably didn’t reach Summit County, was the fifth recorded this year.

The dust arrives from the Greater Colorado Plateau in a pattern that happens in Colorado every spring, said Landry, who has studied the dust for about eight years with the nonprofit center in Silverton.

Summit can expect more dust, he said, because the storms usually happen in March, April and May.

The reddish splotches at the resorts and the particles on your car likely blew in from eastern Utah, northeastern Arizona or northwestern New Mexico.

The color comes from iron oxide, a compound that Landry said isn’t known to cause water-quality problems. The dust also brings calcium, he said, which could be good for acidic waters.

The sun’s rays can still reach the dust if it’s only a few inches under a layer of fresh snow, Landry said, and layers of dust combine during the season to dramatically increase the speed of the snowmelt.

If the weather turns dry and stops bringing more snow to dilute the effect of the dust, streams could surge to extreme peak flows.

The Colorado mountains have been receiving this dust since the last ice age, Landry said, but evidence shows the size and frequency of the storms have increased since the mid-1990s.

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