Snowpack dust is trending upward

This year not as bad as 2013’s ‘quantum leap’

The San Juan Mountains, as seen Friday from Bloomfield, N.M., hold about 80 percent of average snowpack. Researchers are noting increasing dust storms in Southwest Colorado, and that they threaten to create earlier spring runoffs. Enlargephoto

JERRY McBRIDE/Durango Herald

The San Juan Mountains, as seen Friday from Bloomfield, N.M., hold about 80 percent of average snowpack. Researchers are noting increasing dust storms in Southwest Colorado, and that they threaten to create earlier spring runoffs.

The good news is that this year’s dust storms have not deposited as much grit on this area’s snowpack as last year’s.

The bad news: Last year “broke the sound barrier” for dust deposits, and this year is continuing a decade-long increase.

That’s according to the latest measurements by the Center for Snow and Avalanche Studies. The Silverton-based organization runs a study for Colorado and regional water-management agencies.

“The notable thing is that we are still on that same pace,” Chris Landry, director of the center, said Friday afternoon just after posting the most recent report on www.codos.org. “That is a pace where the frequency of dust events is much higher than it was 10 years ago.

“We’re not retreating back to the 20th century, when the frequency of these events was much lower,” he said.

What it means in terms of how it affects humans is, first of all, very possibly the snowpack will melt sooner than normal.

Weather to come will still have a large effect, but the bottom line is that when dust settles on the snow’s surface it “dramatically advances” the rate at which snow melts. White snow reflects much of the sun’s energy, but darker-colored dust particles absorb that energy, heat up and contribute to the melting of the snow. That means spring runoffs occur sooner, affecting everyone from farmers and ranchers to river runners.

Another, perhaps less-obvious effect, is that dust in the snowpack can cause a destabilizing effect in the snowpack, making spring avalanches more likely in the backcountry. There’s little that skiers can do to combat that – even skiing earlier in the day may not help, Landry said.

And large dust deposits have a more obvious effect.

“Dust is miserable to ski on,” Landry said. “Essentially, you’re skiing on mud.”

Since 2003, the Center for Snow and Avalanche Studies has kept track of dust events in Senator Beck Basin just to the northwest of Red Mountain Pass. This snow season, five such events have been catalogued in the basin.

We’re just entering the biggest month for dust storms, Landry said, but so far, it hasn’t been as bad as last year. On April 8, 2013, a dust storm brought a measured 47 grams per square meter of dust. That single event was greater than any other year that’s been measured. Another storm April 15-17, 2013, brought a whopping 9 grams.

“Last year really was a quantum leap in total mass,” Landry said.

Studies show that most of the dust comes from the greater Colorado Plateau, an area that includes all the Four Corners states. Dust storms are exacerbated by soil conditions (drought, for example) and soil disturbance, Landry said.

Although 10-plus years of study was not in itself enough to convince Landry of the certainty of a continuing trend toward dustier snowpack, a paper by Janice Brahney of the University of British Columbia did. Brahney’s study “very clearly verified” a 200 percent increase in dust deposited in western Colorado since the mid-1990s.

“Her paper really validated what was sort of glaring, obvious, but not statistically sound trend in our own dust log,” Landry said. “Now, I do say that this frequency and intensity of these dust storms has definitely increased in the last decades and maybe most dramatically in the last eight to 10 years.”

Overall so far this season, the Center for Snow and Avalanche Studies categorizes dust deposits as “moderate to heavy” and snowpack as “average” for the Senator Beck Basin.

Snowpack in the basin that includes the Animas, San Juan, Dolores and San Miguel rivers was 82 percent as of Friday, putting it below average.

johnp@durangoherald.com