Study Reveals Hidden Water Crisis Below Colorado River Basin

Scientists have documented a hidden water crisis unfolding beneath the Colorado River Basin, one that may prove more consequential than the visible drought afflicting the region's two largest reservoirs, according to reporting by KVIA based on a study published in Water Resources Research.

Researchers from Virginia Tech compared NASA satellite measurements with estimates of surface water, soil moisture, and snowpack between 2004 and 2023. They found groundwater declining across the entire basin during those two decades, with losses accelerating after 2019. A severe drought from 2020 to 2022 triggered especially sharp declines and an unexpected shift in where those losses occurred.

Historically, groundwater has diminished more rapidly in the lower Colorado River Basin, which encompasses California, Arizona, and Nevada. The upper basin—covering Colorado, New Mexico, Utah, and Wyoming—had remained more resilient because its aquifer reserves benefit from snowmelt flowing from the Rocky Mountains. But between 2020 and 2022, groundwater in the upper basin fell by approximately 17.4 cubic kilometers, nearly double the rate in the lower basin, where the decline was roughly 9.4 cubic kilometers.

"The system has reached a tipping point: the upper basin is currently experiencing rapid groundwater loss," the study's authors wrote, according to KVIA. The Colorado River supplies water to nearly 40 million people across the Southwest.

Esther Oyedele, a Virginia Tech graduate student in geosciences and study author, noted that Lakes Mead and Powell represent only part of the region's water resources. "Groundwater is another essential component," she said, according to KVIA.

Groundwater and surface water exist in delicate balance: precipitation and snowmelt seep into soil and recharge aquifers, while groundwater can flow into rivers and lakes through springs. The study found significant differences between the two basins. The upper basin receives more precipitation than the lower basin, which is typically warmer and drier, and snowmelt plays a much larger role in recharging its aquifers. Prolonged drought, rising temperatures, and reduced snowfall are placing additional strain on the upper basin.

A previous study concluded that the volume of groundwater extracted from the Colorado River Basin over the past two decades would have filled Lake Mead. Jay Famiglietti, an Arizona State University professor and coauthor of that earlier research, told CNN that both studies underscore how groundwater accounts for the largest share of water losses across the basin, even though surface water dominates policy and management discussions.