The Colorado River supplies water to 40 million people in seven states and parts of Mexico. The only problem? It’s been experiencing a “megadrought” since 2000.
In fact, studies found that 2000 to 2021 marked the driest period in the Colorado River Basin in the last 1,200 years, due to declines in snowfall runoff from Colorado and Wyoming mountains.
But new research out of the University of Colorado Boulder gives reason for hope.
While temperature increases due to climate change are a major factor in decreases in snowfall runoff, they don’t paint the whole picture.
A climate model analysis from the University of Colorado Boulder’s Cooperative Institute for Research in Environmental Sciences posits that precipitation is also an important indicator of the river basin’s health.
The good news? Scientists are forecasting a 70% chance of increased precipitation over the next 25 years compared to what they’ve seen over the past two decades.
“It’s sort of a nuanced message,” Balaji Rajagopalan, co-author of the study, said in a statement. “The temperature is warming, but that’s not the full story — you add precipitation and you get a fuller picture.”
This full story was published in the Journal of Climate last month, a result of data analysis of flow records at Lee’s Ferry, the dividing point of the river’s upper and lower basins. Rajagopalan and his research partner, Martin Hoerling, looked at records dating back to 1895.
They confirmed that natural changes in participation have fluctuated for much of that time, dictating extreme wet and dry periods for the river.
“We find it is more likely than not that Lee Ferry flows will be greater during 2026-2050 than since 2000 as a consequence of a more favorable precipitation cycle,” Hoerling, the paper’s lead author, said in a statement.
“This will compensate [for] the negative effects of more warming in the near term.”
During the past two-plus decades, about 12.5 million acre-feet of water per year flowed down the Colorado River, which is significantly short of the 14.5 million acre-feet norm.
Well, the norm prior to the early aughts.
Using climate models, including the latest projections from the IPCC, the study’s researchers predicted the river’s flow 25 years into the future, suggesting that flows could rise to 13.5 million or 14 million acre-feet averages between 2026 and 2050.
“So much of the conversation has been that there’s almost a foregone conclusion that we’re only going to see less water in the Colorado [River],” Nanette Hosenfeld, senior hydrometeorologist at the Colorado Basin River Forecast Center, told the Colorado Sun.
“I think this [study] just does a good job of raising awareness that that’s not necessarily true.”
Although these predictions are promising, there is still a chance that conditions could get worse. According to Hoerling, there is a roughly 4% chance that Lee Ferry flows could decline another 20% in the next quarter century, yielding only 10 million acre-feet a year.
That means officials and policymakers must prepare for both outcomes, as they navigate the ebbs and flows of river management for the future.
“Decision makers are confronted with a more optimistic vision of the available supply in coming decades than might have generally been foreseen previously,” Hoerling said in a statement, “but also confronted with a small, but perhaps unacceptable, risk for historically low flows.”
Tribal nations, environmental groups, and academics are all working to propose guidelines for storing and releasing water from the basin’s reservoirs — and states along the river basin released competing proposals in March after tense negotiations.
The Upper Basin proposal would require states in the Lower Basin to start conserving water if the reservoir levels fall below certain points, while the Lower Basin proposal would require all seven states to cut water usage.
Ultimately, decision makers have until 2026, when the current rules expire, to finalize the guidelines that will govern the future of the river. Although it’s complicated to approach from a policy perspective, Hoerling hopes the science will provide a fresh lens.
He told the Colorado Sun: “I think what’s important to recognize here is that the future doesn’t have to be seen as a downhill-only prospect.”
Header image courtesy of U.S. Geological Survey