The snowpack’s dirty little secret
October 17, 2007
GLENWOOD SPRINGS When a winter storm hit Colorado on Feb. 15, 2006, it had a profound effect on the state’s snowpack that year, but not how you might imagine.The storm consisted of dust, not snow. And the dust’s heating effects caused snow to melt off weeks earlier than it would have otherwise, researchers say.This year, the Silverton-based Center for Snow & Avalanche Studies continued to document the phenomenon of dust storms speeding up the melting of snowpack. And now it’s trying to use its findings to help the state’s water agencies do a better job of anticipating when snowmelt will occur, so they can better manage water supplies.On Tuesday, Chris Landry, executive director of the Center for Snow & Avalanche Studies, updated the Colorado River District board in Glenwood about the center’s efforts.He said the center, working with other research entities such as the Boulder-based National Snow and Ice Data Center, is finding that dust storms can advance snowmelt by up to a month, producing “a flashier snowmelt, a more intense snowmelt that lasts shorter in duration.”Landry said clean snow is the most reflective land surface on earth. Snow’s reflective power is called albedo, and clean snow’s albedo can approach 100 percent. But darker, dirtier snow may reflect only 50 to 60 percent, meaning the rest of the energy is absorbed.”That’s a very dramatic effect on energy balance in the snowpack,” he said.Much of the dust is believed to come from Western deserts, and there are concerns that it may be increasing due to factors such as drought and grazing. Landry said Colorado experienced nine “dust events” during the winter of 2005-06.Much of the center’s work is focused on digging snow pits and doing other high-mountain, on-snow research at a site in southwest Colorado.”It takes a lot of people, a lot of work. It isn’t all bad,” said Landry, a former Roaring Fork Valley resident who earned acclaim for his pioneering extreme skiing exploits locally.The same telltale layers of dust in the 2006 snowpack showed up at several Colorado sites, including near Loveland and Hagerman passes. And snowmelt accelerated in a corresponding fashion.Tracking snowmelt this year, researchers showed it increasing sharply whenever dust was on the surface. Fresh snow cover would allow snowpack to recover, but once that snow melted and a dust layer was re-exposed the snowpack again would start dissipating quickly.”It was on again, off again all spring,” Landry said, displaying a graph of his findings to the river district board Tuesday. “Those spikes correspond perfectly with fresh snow cover. It’s just like a switch.”The center’s work has been funded with the support of the Colorado River District and similar districts elsewhere in Colorado. The river district gave it $8,000 last year, and the center is asking for funding again this year.The center has been sending supporting districts alerts when dust storms occur. It also is working on models that can be used to better predict what such storms will do to snowpack. In addition, it hopes to help develop a regional network of “dust-in-snow” observations.For water districts, such information could be crucial to timing releases of water from reservoirs. It’s helpful for them to know when the snow is expected to be melting, and when a watershed will reach the point of what Landry calls “SAG” – snow all gone.Colorado River District general manager Eric Kuhn said such information also can be helpful in evaluating whether reservoir storage will be adequate to meet needs throughout the summer.