Dust storms accelerated by a warming climate have covered the Rocky Mountains with dirt whose heat-trapping properties have caused snowpacks to melt weeks earlier than normal, worrying officials in Colorado about drastic water shortages by late summer.
Snowpacks from the San Juan Mountains to the Front Range have either completely melted or will be gone within the next two weeks, said Tom Painter, director of the Snow Optics Laboratory at the University of Utah and a leading expert on snowmelt.
The rapid melting is linked to a spate of intense dust storms that kick up dirt and sand that in turn are deposited on snow-topped mountains. The dust darkens the snow, allowing the surface to absorb more heat from the sun. This warms the snow -- and the air above it -- significantly, studies show.
The problem has been particularly acute in the semiarid Colorado Plateau region encompassing parts of Utah, Colorado, New Mexico and Arizona. An unprecedented 12 large dust storms have occurred so far this year in the region, and at least two more are projected in the coming months, officials say.
"Already we have more than doubled the amount of dust we've typically observed during the last six years," Painter said.
The early snowmelt could spell disaster for thousands of farmers and ranchers in the region who depend on slowly melting snow to provide water flows over the dry summer months, said Scott Brinton, assistant division engineer in the Colorado Division of Water Resources' Southwest regional office.
"Those people who were relying on the mountain snowpack are going to have difficulty later in the year," Brinton said.
There are also broader implications as arid Western states wage costly legal battles over access to water supplies that are dwindling, in part, because of early snowmelt.
Colorado -- which is under an agreement with the Bureau of Reclamation to divert roughly 38 million gallons a year from the San Juan River Basin to thirsty cities in New Mexico, including Albuquerque and Santa Fe -- now fears it may not be able to meet the terms of the water transfer agreement as the snow melt arrives early and flows downstream.
Meanwhile, managers are working to empty reservoirs as quickly as possible across southern Colorado and New Mexico as huge volumes of melt water course down mountain streams. Rapidly melting snow in the San Juan Mountains forced Reclamation managers last week to release water from the El Vado Reservoir in north-central New Mexico at its fastest rate in four decades, said Mary Perea Carlson, an agency spokeswoman.
"When it started coming down so rapidly, we realized we'd better make some room," Carlson said.
But once the water is gone, it is gone for the year.
"There's not a whole lot we can do about it," Brinton said. "We're telling people, 'You'll be getting your water early this year, so use it while it lasts.'"
A growing problem
Early snowmelt is not a new problem the West, but its causes are becoming increasingly well known to scientists who have studied the phenomenon.
Dust storms, one of the main contributors to the problem, are a key culprit, and they promise to grow worse as grazing, mining and increased recreational use remove vegetative cover and to expose loose soils to wind.
And the problem could grow worse as the Obama administration pushes to open millions of acres of federal land across the West to renewable energy development, including wind turbines, solar arrays and geothermal plants (Land Letter, May 7, 2009).
Construction of these projects, along with the construction of tens of thousands of miles of transmission lines needed to carry renewable electricity to population centers, has the potential to disturb a great deal of parched land, creating ideal conditions for dust storms, said Jayne Belnap, a U.S. Geological Survey research ecologist in Moab, Utah.
"I'm not saying we have to stop energy development, but we've got to be smart about it," Belnap said.
Humans exacerbate the problem in other ways, too.
The Department of Energy's Pacific Northwest National Laboratory, in a groundbreaking study released in January, found that soot pollution emitted from vehicle tailpipes and industry smokestacks are helping to melt snowpacks from the Rockies to the Sierra Nevada and Cascade mountain ranges. (Land Letter, Jan. 22).
Like dust, airborne soot is carried on wind currents to higher elevations where it settles on the snow-topped mountains, creating a dark-colored dirt layer that absorbs solar energy and melts the snow.
It is all part of a cycle, researchers say, in which the warming climate at lower elevations creates conditions that exacerbate pollution problems in the snow-topped mountain peaks, reducing the the snow's reflective capacity and soaking up more heat.
This year is a classic example, said Painter, whose Snow Optics Laboratory operates a system of monitors that measures snow reflectivity across the Rockies.
Researchers in Painters' group realized the West was poised for a bad dust season when snow and rainfall all but stopped in the Colorado Plateau region in January, February and March -- typically high-volume precipitation months. Meanwhile, warming temperatures at lower elevations prompted plants to bloom before they had sufficient water, and the resulting dead vegetation exposed the parched soil underneath, creating more dust.
"We were expecting this," Painter said. "But even when you're expecting something you don't always necessarily want to believe your eyes."
Shifting sands, rolling dunes
Another growing source of dust is the vast sand dune landscape that stretches thousands of square miles across the Four Corners region of northeast Arizona and northwest New Mexico, which over the last century has converted from a rolling grass prairie to a kind of desert plateau.
Margaret Hiza, a USGS scientist who has studied change on the Navajo Nation's sprawling Four Corners reservation, said steadily warming temperatures have created drought-like conditions that have killed the vegetation that held the sandy soils in place.
The exposed sand is whipped by high winds, allowing the dunes to spread rapidly across the Navajo reservation, where they threaten to smother fragile ecosystems. Native plants like rice grass and purple sage that are wiped out are replaced by foreign invasive species such as Russian thistle or tumbleweed. The non-native plants do not hold the soils together as well, further exacerbating the problem of loosening soils.
The blowing sand also causes a number of other problems, including respiratory distress for local residents and disrupting highway traffic.
"It could just turn the whole Navajo Nation into a dust bowl," said Hiza.
Painter and his colleagues, studying a disastrous 2006 dust storm season that helped melt snowpacks in southwest Colorado's San Juan Mountains, determined that the dust came from hundreds of miles away, including Navajo country.
"There's good evidence that northeast Arizona is strong in contributing to dust deposition in the mountains," Painter said.
No easy solutions
While the problem is increasingly well-documented, solutions are proving more elusive.
While some have called for restoring native grasses and other soil-stabilizing species across the region, such activities cannot occur so long as the soils continue to blow away.
Hiza, the USGS scientist, is organizing a pilot project this summer near Winslow, Ariz., that will attempt to replicate successful dune stabilization efforts in northern China. The project calls for embedding straw mats about 10 square feet in diameter into the dunes, with about 4 inches of mat exposed above the dune line. While the mats allow some sand to move across the surface, they help stabilize the subsurface and hold the dune intact.
"It's tricky to try and slow moving sand down," she said. "But once it stops moving, plants can start growing on it again."
Other options, including those aimed more directly at water supply, are to seed clouds with the hopes of increasing snow volumes in the high-elevation mountains. Local governments and power companies spend tens of millions of dollars a year on such seeding projects that have been shown to increase snowpack.
But, experts say, such efforts are increasingly undermined by dust and soot accumulations that increase the melt rate of snowpacks, regardless of their depth.
And the problems will persist as long as the Western climate continues to warm, perhaps by as much as 7 degrees Fahrenheit over the next 90 years, according to the Intergovernmental Panel on Climate Change.
If such conditions persist, Painter said this year's dust storm intensity and early snowmelt could become the norm across the region.
Belnap, the USGS research ecologist, said focused attention could help reverse the trend, but it will take more effort on the part of government and landowners.
"We do not manage for dust. We don't even think about it," she said. "I think the time is coming where we are going to have to decide we need to think about dust."
Scott Streater is a freelance journalist based in Colorado Springs, Colo.