A new paper analyzing climate models finds that eastern Colorado is likely drying out faster than western parts of the state due to climate change, potentially exacerbating a critical mismatch in water resources across the state.
Earlier research has established that both regions will likely grow more arid due to human-caused global warming. By running a series of global climate models, researchers at the National Center for Atmospheric Research in Boulder found that the trend is more pronounced and occurs sooner east of Colorado’s Continental Divide.
The trend could amplify a division that has defined the state’s water politics for more than a century, said Alex Rugg Stebbins, a lead author and a project scientist at NCAR.
In Colorado, roughly 80 percent of the water originates in rivers west of the Continental Divide. Meanwhile, almost 90 percent of Colorado's population lives in rapidly growing communities on the Eastern Slope, such as Fort Collins, Colorado Springs and Denver. That split is why water utilities operate sprawling systems of pipelines and reservoirs to deliver water from the Western Slope to thirsty Front Range communities.
“The growing population and drying in the east is going to mean cities like Denver, Boulder and Longmont are going to become even more dependent on water we take from the west,” Rugg Stebbins said.
The study was published online Sept. 10, following a peer review process. A finalized version is set to officially print in the journal Environmental Research Communications.
The study examines measures of dryness like runoff levels and soil moisture. Those metrics swing back and forth under normal conditions depending on annual weather and more prolonged climate patterns like El Niño and La Niña.
By running climate models, the researchers estimated when climate change pushes a region outside the normal range of variability. In other words, the paper attempts to pinpoint when the “signal” left by global warming overpowers the “noise” of normal, historical climate fluctuations.
Stebbins said soil moisture offers a clear example of the split: In eastern Colorado, evidence of climate change drying the soil was evident by 1970, compared with 2022 in western Colorado. By 2100, the drop in soil moisture in eastern Colorado will roughly double the decline in western Colorado, according to the modeling predictions.
Previously published climate research has focused on the Western Slope since it serves as the headwaters of the Colorado River Basin.
A “megadrought” across the region has led to the driest conditions in at least 1,200 years, straining a river known for delivering water to about 40 million people in the southwestern U.S. and northern Mexico. Another recent study closely linked those dry conditions to human activity.
Stebbins, who lives in Longmont, said climate researchers should pay more attention to eastern Colorado. After all, the faster the region dries out, the more Front Range communities will demand water otherwise bound for cities like Las Vegas and Phoenix, further down the Colorado River.
“Our water usage affects canyons and lakes and cities pretty far away from us,” Stebbins said.
