The story Susan Behery tells about dust blowing into Colorado from New Mexico and Arizona sounds almost Biblical, like cows dropping dead in their owners’ fields or swarms of locusts devouring their crops.

A hydraulic engineer for the Bureau of Reclamation in Durango, Behery says she once saw dirt falling from the sky in the manner of rain. It was so heavy, she said, it splatted when it hit the ground. When the storm that brought it moved on, a brown residue covered Behery’s car, her lawn furniture, her house. In fact, it covered the town of Durango, the town of Silverton and the San Juan Mountains, where Behery’s colleague, Jeff Derry, does the bulk of his work as the executive director and lead scientist for the Center for Snow and Avalanche Studies and its Dust on Snow program.  

Behery says she and Derry work closely together. This time of year they talk by phone almost daily. That’s because Derry studies dust that travels to Colorado from northern New Mexico and Arizona. When it arrives here, in storms stopped short by the mountains, it settles in a distinct brown layer on the snow.

Derry’s main job is monitoring the dust layer (or layers) for water managers like Behery, because dust on snow is a major contributor to how much of the water in Colorado’s snowpack reaches the creeks, rivers and reservoirs that serve our state, and when the flows of those creeks and rivers reach their peak. That, in turn, impacts how Behery and her colleagues in water management control things like the levels of river water flowing into and out of reservoirs, of which Colorado has many. 

The primary stem of the Colorado River has 15 dams and its tributaries have hundreds more. Each major tributary flows out of a river basin reliant on snow. “But we’ve been having these sporadic good precipitation years with lots of drought in between,” Behery says. And drought years lead to low snowpack, which, when coupled with dust, disrupts rivers.  

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