SALT LAKE CITY — The Colorado River is a vital water source for a large chunk of the West, including Utah.
It’s believed that about 60% of Utahns directly benefit from the river, which accounts for some of the 40 million Americans who rely on it for water.
However, drought and overconsumption across the river’s basin have left its future in question, as the seven basin states seek a long-term solution to manage it. A recent University of Utah-led study better demonstrates how dust has factored into the river’s struggles over the past two decades, which could change future water forecasts.
“The degree of darkening caused by dust has been related to water forecasting errors. The water comes earlier than expected, and this can have real-world impacts,” McKenzie Skiles, director of the University of Utah’s Snow Hydrology Research-to-Operations Laboratory and the study’s co-lead author, said in a statement.
“If we can start to build dust into the snowmelt forecast models, it will make water management decision-making more informed,” she said.
The Colorado River’s woes have been well documented, including a puzzling pattern of spring runoff averages falling below snowpack collections. This has been tied to a few trends, including overconsumption, as communities consume more water than is being added to the system, Gene Shawcroft, chairman of the Colorado River Authority of Utah, explained last year.
Dry soil moisture can also factor into the West’s snowmelt process, sending more water toward recharging groundwater sources before ending up in creeks, streams and rivers.
Researchers also found a link between dust and poor snowmelt along the Colorado River Basin. Dust contributed to earlier snowmelt and lower totals, according to a study published 15 years ago in the Proceedings of the National Academy of Sciences of the United States of America.
Skiles has built on the research since then, authoring a 2018 study that linked dust with snowmelt issues along the Great Salt Lake Basin. That’s because dust composition is darker than snow, heating up faster in sunlight and causing snow to melt faster. This, in turn, led to worse runoff efficiencies.
“That’s not currently accounted for in our (snow water equivalent) forecasting models. It introduces errors into our understanding (of) when snow is going to run out of the mountains,” she explained.
The newest study, published last month in Geophysical Research Letters, better explains how this happens along the Colorado River system by a review of “daily remotely sensed” satellite imagery between 2001 and 2023.
Through reviews, researchers found dust impacts “tend to be largest” in “lower alpine elevations” of about 9,180 feet to 11,480 feet. Dust was also found in other parts of the study area, typically in the mountains after spring storms passed through desert regions. Some of these large dust plumes were even picked up in satellite imagery.
The dust, the team determined, was adding to daily snowmelt rates of up to 10 millimeters per day.
“Even an extra millimeter per hour can make the snowpack disappear several weeks earlier than without dust deposition,” said Patrick Naple, doctoral candidate at the University of Utah, and the study’s co-lead author.
Meanwhile, researchers added that no “straightforward relationship between aridity and dust” was found, which they found interesting. That meant dust was still ending up in the mountains even when there wasn’t an active drought in the region, although they noted that the study took place during the West’s “megadrought.”
The event, which started in 2020, made it difficult “to know what is ‘normal’ at longer time scales,” they wrote.
This could impact the Upper Colorado River. Researchers hope that accounting for dust will improve future water forecasts across the region, as experts remain puzzled over snowmelt rates.
Skiles adds that the findings could help reservoir managers decide when to store snowmelt on an annual basis. The findings come as the seven basin states continue negotiating the long-term water use of Lake Powell and Lake Mead, the nation’s two largest reservoirs.
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