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Dust storms hasten snowmelt

JERRY McBRIDE/Durango Herald

What snow that remains on the La Plata Mountains has been partially covered with dust from the recent storms, and that will cause the snow to melt faster.

By Dale Rodebaugh Herald staff writer

The dust storms that have bathed Southwest Colorado in recent weeks are poised to contribute even more misery in a drought year.

When the dust layers deposited on mountain snow April 8, April 14 and the 61-hour monster of April 15-17 come under a scorching sun, the already measly snowpack could melt into nothing in no time, the director of the Center for Snow & Avalanche Studies in Silverton said Thursday.

The albedo, the reflectivity of the Earth’s surface – dirt, sand, snow, ice – is key, Chris Landry said.

Clean snow absorbs 5 to 20 percent of solar energy, but dust-covered snow absorbs 70 percent, Chris Landry said. The more energy absorbed, the faster the melt, he said.

“Direct solar energy is bad news,” Landry said. “Air temperature is a relatively minor factor.”

The major dust event of the season so far – the sixth – occurred April 8, Landry said. The seventh occurred April 14. A break followed, then came the 61-hour assault.

A dust season, like a fire season, begins with the first event. In the case of dust, the first dust storm occurred in November, Landry said.

Landry cautioned against being fooled by the pristine whiteness of the mountains.

“They look white now because we’ve had some snow,” Landry said. “But it will last only until the sun comes out.”

The dust arrives from northwest New Mexico and the Little Colorado River basin in Arizona, borne by wind from the south, southwest and west.

“We’re retaining snow longer this year than last because of March and April storms,” Landry said. “But the water equivalent is no greater than last year.”

Runoff will surge when the three dust layers merge,” Landry said.

It appears that more than a little snow is needed to make a difference.

In a report to Montezuma County commissioners, John Porter, president of the Southwestern Water Conservation District, said mountain precipitation in the Animas, San Juan, Dolores and San Miguel basins in March was 56 percent of average. Stream flow in the basins from April to July is expect to range from 46 to 61 percent of average, Porter said.

Jim Dyer, a Marvel sheepman, is no stranger to dust storms and is getting by on a skimpy amount of water.

“We expect dust storms here in the spring – dust and a sprinkle of rain and we have mud on the windows,” Dyer said. “I’m surprised that the recent storms took Durango by surprise.”

Dyer counts on rain to produce forage for his sheep. When rain is scarce – like now – he keeps them in a pen and feeds them hay.

“You know what hay prices are,” Dyer said, a reference to the scarcity of hay that has driven up prices throughout the West.

A minuscule amount of water from the Treanor Ditch off the La Plata River fills a storage pond from which, through drip irrigation, Dyer waters a garden and orchard.

The outlook for agriculturists like Dyer whose livelihood depends on rain and snow isn’t bright.

“There’s a potential that it’s going to be a less than average year,” Sterling Moss, director of the Natural Resources Conservation Service office in Durango, said Friday. “Soil moisture – 18 to 20 inches of depth – is half to two-thirds of what we should have after a normal winter.”

Others aren’t enthusiastic about the forecast, but they’re not despairing, either.

Tom O’Keeffe from the Durango Rafting Co. isn’t sweating it yet.

“The snowpack is 72 percent of normal, and it was 44 percent this time last year,” O’Keeffe said, “The current cold is not pleasant, but it holds off the melt.”

O’Keeffe has five outings booked from Thursday through May 1.

Drew Beezley at 4 Corners Whitewater agreed that low temperatures that delay snowmelt benefit rafting companies.

“The commercial clients aren’t here yet,” Beezley said. “Last year, the runoff was too early.”

But rafting can be pleasurable even with a low flow, Beezley said.

Landry and his assistants aren’t pursuing a topic of only academic interest.

Water interests throughout the state fund the center for the practical information it provides. Water districts, the Bureau of Reclamation, the Colorado Water Conservation Board and state flood-control officials put snowpack information to use. Butch Knowlton, director of emergency preparedness in La Plata County, is on the list of Landry’s email recipients.

“Landry’s information is a great asset for water managers,” Bruce Whitehead, executive director of the Southwestern Water Conservation District, said. “He monitors snow levels, dust events and snowmelt, which helps us project runoff.”

daler@durangoherald.com

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