Think like a watershed: Interdisciplinary thinkers look to tackle dust-on-snow

Cortez symposium focused on solutions

🥵 Aridification Watch 🐫

Satellite images of multiple dust plumes over the Four Corners region in April 2013. NASA images courtesy Jeff Schmaltz, LANCE MODIS Rapid Response.

I must admit that when I was invited to attend a symposium in Cortez, Colorado, focused on dust on snow, I was a bit hesitant to accept. Six hours of talking about dust and snow? I thought. How is that even possible? 

I found that it’s not only possible, but that six hours of dusty snow talk can be downright compelling and super informative, even for someone who has been steeped in the topic for years. 

The Nexus of Land and Water symposium, hosted by the Wright-Ingraham Institute and Mountain Studies Institute was the culmination of six months of work by 21 researchers, including scientists, artists, water professionals and community leaders. While the science of dust-on-snow was covered, the main focus was on possible solutions to the vexing problem that has serious implications for Southwestern water supplies. That’s because, as the Mountain Studies Institute’s Jake Kurzweil put it, “This is not an issue that will be solved by science … it will be solved by communities.”

Nicholas Webb, Research Physical Scientist at the Jornada Experimental Range Research Unit, points out high-risk regions in the Southwest.

Background: Each winter and spring, winds kick up in the Southwest, usually in advance of big snow or rain storms, and mobilize massive dust plumes, which then travel across the land. When the storm front hits the mountains it dumps its load of dust on top of the existing snowpack, coating the surface with a reddish-brown tinge that reduces the snow’s albedo, or its ability to reflect solar energy. 

This happens repeatedly over the year, with the biggest “dust events” typically occurring in spring. As the snow begins melting, the dust levels consolidate, further lowering albedo and allowing the snowpack to absorb more solar energy. That speeds up snowmelt, which affects the region’s ecosystems and water supplies. And that dries out soil and frees up more dust for the wind’s taking.

Scientists have been studying this phenomenon and the way it affects the San Juan Mountain snowpack (and those in other mountains) for over two decades. Findings that emerged from that research include: 

• Dust on snow speeds up snowmelt and results in earlier runoff, which can affect water management and streamflow forecasting. 

• Dust on snow is even a bigger factor in snowmelt rates than warming temperatures. S. McKenzie Skiles, director of the University of Utah’s Snow Hydro Lab, called the dust on snow phenomenon “the most dramatic thing I’ve ever seen.” 

• The faster snowmelt also results in lower yields, meaning there is less water overall flowing into rivers and reservoirs. 

• Dust events have been occurring for thousands of years, but picked up significantly beginning around 1850 following the first white settler-colonist influx and associated land disturbance (most notably from livestock grazing). Dust events peaked in the first few decades of the 20th century, when volumes of dust were five times higher than they were prior to colonization. They then dropped off a bit following the passage of the 1934 Taylor Grazing Act and have held more or less steady ever since.

  

  A February 1932 news item.

• The dust that is deposited on the San Juans comes from the Four Corners region; some of the most prolific sources are on the Navajo Nation. 

• Dust events occur every year, with some “extreme” seasons seeing four or more times the frequency and volume of dust deposited than during “typical” years. And while the body of knowledge of the phenomenon continues to grow, it has not yet reached a point to enable accurate forecasting of the events or seasons. 

“Now it’s time to say, What can we do about it?” Skiles said. “How do we live with dust on snow?” 

Dusty pumpjacks near Aneth, Utah, and the Animas Valley north of Durango, Colorado, during a dust event. Jonathan P. Thompson photos.

In some ways, the answer is simple: You keep the dust on the ground, where it belongs. And you do this by restoring the landscape, increasing soil stability, and minimizing future disturbance. Of course, pulling that off, in an economically and culturally appropriate way, is anything but simple, and even well-intentioned efforts can go terribly awry.

Len Necefer (Diné) pointed to the Navajo Livestock Reduction program as an example of such a tragic mistake. After Hoover Dam began backing up water in 1933, officials began worrying about the reservoir behind it filling up with silt and rendering the structure useless within decades. And those same federal officials erroneously determined that the sole source of silt was overgrazed lands on the Navajo Nation. So the Bureau of Indian Affairs’ John Collier ordered the extermination of hundreds of thousands of Navajo sheep. While the program may have been effective in reducing the impacts of grazing (if not in lessening siltation), the way it was carried out was also traumatic and economically devastating, given the importance of the animals to Navajo culture. “It still affects people today,” Necefer said.  

Avoiding these sorts of situations requires working with the communities in a bottom-up, grassroots way, with respect for the local people, their culture, and the landscape. An approach may work well in one place, but fail utterly in a neighboring valley. 

A summer dust-event forming near Hovenweep National Monument. Jonathan P. Thompson photo.

San Luis Valley

Map showing evapotranspiration of center-pivot-irrigated fields in the San Luis Valley. Source: OpenET

The complexity of the dust on snow situation is playing out in the San Luis Valley of southern Colorado. The broad valley, bordered by the San Juan Mountains on the west and the Sangre de Cristo Mountains on the east, sits atop a dual-layered aquifer system. The aquifer supports the streams, most notably the Rio Grande, which originates in the San Juans and cuts eastward across the valley before turning southward to New Mexico, Texas, and Mexico. Streamflow returns the favor by replenishing the aquifer. 

Both the aquifer and the streams, in turn, are drawn upon to irrigate about 300,000 acres of crops, including potatoes, alfalfa, and barley, often using center-pivot sprinkler systems that paint a patchwork of green, 120-acre circles across the valley floor.  

Groundwater pumping for irrigation has drawn down the aquifer. Meanwhile streamflows have also declined steadily over the past decades, further exacerbating the aquifer’s shrinkage. Some of this is surely due to lower snowpack levels. But Patrick O’Neill, a San Luis Valley agronomist, suspects something else is also in play. He noted that last year’s streamflows ended up being about 70% of what was forecasted based on spring snow levels. In other words, something had pilfered some of the water that had fallen on the Rio Grande’s headwaters. The primary suspect is dust-on-snow, though science has yet to prove the phenomenon’s guilt.

As water supply has declined, demand has remained steady. Now, according to O’Neill, the valley’s water supplies are at least 40,000 irrigated acres overshot. What that means is that farmers have to stop irrigating about 330 of those circular fields to bring demand and supply back into balance. Again, the solution seems fairly straightforward: Stop pumping groundwater and growing water-intensive crops. Incentives are available to farmers who fallow their fields, and penalties levied on those who pump too much groundwater. 

But as Madeline Wilson, an agricultural systems specialist for Colorado State University’s extension office pointed out, each one of those fields also represents a family. “We’re not just talking about drying up lands,” she said, “but the drying up of our economy.”

And then there’s the dust. If a field’s irrigation is simply cut off, or if it is not revegetated properly, it ends up being little more than a noxious weed crop or a 120-acre dust patch. The winds will kick that dust up, too, deposit it on the snow, and, well, you get the picture: It’s the big, aridifying dust-on-snow feedback loop.

In the San Luis Valley, however, continuing to irrigate at current levels is not an option. So, in order to transition the region to a drier reality, Wilson said, it needs a producer-informed “revegetation playbook … for a multitude of pathways.” And it needs to be socially compatible, ecologically viable, and economically capable, she said. Instead of just drying up the fields, or attempting to re-vegetate with limited water and inappropriate seeds, they could keep the land in food production by reducing irrigation levels, planting drought-tolerant, native forage crops, and converting the fields to seasonal pastures for livestock. They could put greenhouses there and grow more valuable crops with far less water. Some dried out fields could become home to solar installations. 

By the end of the symposium, and after seeing presentations by snow and climate scientists, a “dust guru,” an expert on using fungi to heal land, storytellers, ranchers, artists, and restoration ecologists, I came to realize that even a problem as big and dispersed as dust-on-snow can be solved, or at least mitigated. Yet implementing those solutions would also be a massive challenge, and would require the collective conscious of the Southwest to, as snow scientist Jeff Derry put it, “think like a watershed.” Mostly, though, I was left with a feeling of hope, reassured by the fact that so many smart, and creative, people and institutions were working on the problem. “We are headed somewhere good,” Heidi Steltzer, a climate scientist-turned-Earth-theologian said. “How long we live in the dark depends on the choices we make in every moment.” 

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📸 Parting Shot 🎞️

Hoping this image of the sunrise over Ute Mountain will give you a bit of Election Day serenity. Jonathan P. Thompson photo.