Colorado’s snow is dust-free for the first time in a decade
High Country News
Last March, while kayaking the sandstone labyrinth of Utah’s San Juan River, I was punched in the face with a wall of wind. It howled up-canyon with a biting ferocity, carrying particles of red sand that scoured our faces and forced us into a cave for hours to seek shelter. The next day, as we drove home to Colorado, it followed us, knocking branches off trees and whipping freshly plowed fields into the air. Sand coated my teeth and my windshield. It turned the sky an ominous red.
In the last decade, similar spring storms have dropped an increasing amount of “dust” onto Colorado’s alpine peaks, creating dark, dirty-looking snow that absorbs more sunlight and melts more quickly. This dust-on-snow effect quickens the rate of spring runoff, creating a nasty feedback loop: More dust leads to faster snowmelt, which often leads to summer drought (because there’s no snow left to feed rivers), which in turn kicks up even more dust. Though the grit that lands in Colorado can come from places as distant as China’s Taklamakan Desert, most of it comes from the vast Colorado Plateau, where grazing, development and ongoing drought exacerbate natural dust storms.
This year, however, there appears to be a break in the cycle: Though a few storms have swept east from the plateau, they either haven’t had enough oomph to carry dust to the mountains, or they’re coming from places like eastern Utah where the dust was tamped down by late-winter snowfall. For the first time in a decade, March snowpack across Colorado is virtually dust free. Great news, right?
Not really, says Chris Landry, executive director of the Center for Snow and Avalanche Studies in Silverton, Colorado. Rather than cause for celebration, current dust- and snowpack conditions are about as close to worst-case scenario as you can get. For one thing, above-average temperatures statewide mean that in each of the 11 locations Landry sampled last week, the snow itself was “much warmer than usual. In some places,” he adds, “it was as warm as you can get and still be snow — warmed up all the way to zero degrees Celsius.”
Once snow hits that threshold, Landry says, it’s very unlikely to cool down again — meaning that even if skiers are lucky enough to get a few spring dumps, snowmelt in many places has passed a point of no return. Already, some stream gauges are showing runoff well above annual norms for this time of year.
Secondly, there’s just not much snow to begin with. In most Colorado watersheds, snowfall was subpar, and a long, dry, warm spell that lasted through February caused some slopes to become nearly bare — creating even more variation than usual between sunny, south-facing slopes and cool, shady ones. When Landry tramps around visiting data sites, he’s used to seeing a difference between conditions on the ground and the computer-generated SNOTEL maps, because SNOTEL sample sites tend to be flat and shady. This year, however, Landry worries the variations are higher than usual — so even maps showing snowpack at 67 percent of normal may be overstating what’s really out there. Less snow ultimately means faster rates of melting, and faster melting now means less water in streams and rivers this summer.
The last criteria for Landry’s “worst-case scenario” is a dry spring — which is exactly what we’ve had so far. Just as there have been few storms here in the mountains, there haven’t been many over the Colorado Plateau either, and that means conditions there are getting drier and dustier — primed for a big April dust storm. April is typically the biggest month of the year for dust events, and May isn’t far behind. So just because there’s virtually no dust out there right now doesn’t mean it’s not coming: “The Colorado Plateau is drying out,” Landry says, “And that almost ensures that if and when a major weather system moves through, dust will be available. We’ve had single dust events that in and of themselves would be more than adequate to really alter snowmelt.”
“Everybody is hoping for no dust,” he adds. “And that would be considered a good thing. But it’s also true that we’re a long way from being even reasonably hopeful that will be the case.”
The Colorado Dust on Snow Program at the Center for Snow and Avalanche Studies is a stakeholder-driven, applied-science program that monitors dust at 11 sites statewide. Efforts are funded by the Colorado water community — from local conservation groups to the Bureau of Reclamation — to help water managers cope with the effects of dust on snow.
Krista Langlois is a correspondent at High Country News.
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