A team of researchers has been hard at work in the Rocky Mountains to solve a mystery. Snow is vanishing into thin air.
Now, for the first time, a new study explains how much is getting lost, and when, exactly, it's disappearing. Their findings have to do with snow sublimation, a process that happens when snow evaporates before it has a chance to melt.
Perhaps most critical in the new findings is the fact that most snow evaporation happens in the spring, after snow totals have reached their peak. This could help water managers around the West know when to make changes to the amount of water they take from rivers and reservoirs.
“This lets us make much better decisions and understand processes that there was not data available to understand before,” said Jessica Lundquist, the study’s author. “These data are absolutely critical.”
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Researchers across the western U.S. have been producing increasingly granular data about snow over the past two decades. Eighty-five percent of the Colorado River starts as high-altitude snow in the mountains of Colorado and Wyoming. As climate change and steady demand are putting a strain on the river's supplies, scientists have sought to develop a better understanding of how snow behaves and give policymakers a more nuanced idea of how to manage reservoirs.
Water managers often see a gap between the amount of water they expect to melt into rivers and streams each year and the amount that actually does. A number of climate factors are to blame, such as dry, thirsty soil that soaks up snow melt on its way downhill.
This new data, published in the Bulletin of the American Meteorological Society, helps explain how sublimation also contributes to that gap.
Lundquist said it will help make snow prediction models more accurate. This winter, models projected that 30%-40% of snow would be lost to sublimation. She and her students found that about 10% of snow was actually lost to sublimation, less than models predicted.
“Before this study, there was no place you could get enough measurements to evaluate whether your model was getting all of the different processes right,” Lundquist said.
In March 2023, KUNC visited the research site to watch data collection in progress. It involved a network of more than 100 high-tech sensors, plus a small crew of hardy PhD students trekking through the snow with shovels and old-school hardware to gather measurements.
Those researchers found that wind is a major driver of snow sublimation during colder months, and heat from the sun is a major driver during the spring.
Colorado Snow Survey supervisor Brian Domonkos, who was not involved in the study, said he hopes to see more research like this carried out over a wider geographic range.
“One spot is a great start,” he said. “A study of this depth and this breadth, with all of the sensors that they deployed, is a spectacular start. Ideally, we would love to see this same study, sensors and whatnot, distributed across a number of sites in many locations across Colorado.”
The initial study was carried out in Gothic, Colorado, near Crested Butte. Gothic, a once-abandoned 1800s mining town, has long hosted the Rocky Mountain Biological Laboratory. Each year, legions of scientists live in its cabins and study the natural world.
The site, Domonkos said, experiences a wide range of conditions throughout the winter and is a reasonably good representation of other places in Colorado’s mountains.
Lundquist, the study’s author and an engineering professor at the University of Washington, also wants to see more research on the matter going forward, especially during the spring months.
“Science is often led by the motivation of the scientists, and people love to go do research at places you can ski to in the winter, and places you can hike or drive to in the summer," Lundquist said. “In the mud season, you can't quite ski or hike or drive very well, and it's a little bit harder to do. But that's what we need to do to find the key answers to where the water's going.”
A greater volume of data about snow could help hone forecasts with wide-reaching implications, as water managers as far away as Phoenix and Los Angeles turn to mountain snow data each year to more accurately plan how much water will be available for cities and farms around the Southwest.
This story is part of ongoing coverage of the Colorado River, produced by KUNC in Colorado and supported by the Walton Family Foundation. KUNC is solely responsible for its editorial coverage.
