Last week, news broke that the depletion of groundwater across the Colorado River Basin has been quietly, rapidly outpacing the more visible decline of the river itself. Even as the seven basin states negotiate reduced consumption of river water—inevitably driving dependence toward local aquifers instead—this newly published research shows that the majority ofmost of the water lost throughout the basin in recent years has been underground. In the Lower Colorado River Basin alone, groundwater has accounted for 71% of total water supply loss.  

Jay Famiglietti, a longtime contributor to Ten Across, specializes in the use of satellite data to monitor the world's groundwater mass. His team's new findings focus on the U.S. Southwest—a region at the forefront of the nation's water supply challenges and the complex balances between resource limitations and economic growth.  

As states and cities in the Colorado River Basin and elsewhere develop water management strategies to sustain themselves through future constraints, a growing understanding of groundwater supply is key to effective proactive policy. It is increasingly clear that time is of the essence for this uniquely finite resource.   

Listen in as Ten Across founder Duke Reiter and Jay Famiglietti discuss the concrete findings in this report, the immediate and long-term implications for agriculture in the Southwest, and Jay’s motivations for raising awareness of groundwater usage in the Ten Across region and beyond.  

Relevant articles and resources:  

Read the open access study: “Declining Freshwater Availability in the Colorado River Basin Threatens Sustainability of Its Critical Groundwater Supplies”  

Read The Washington Post’s analysis  

More analysis from The Guardian and Inside Climate News  

Catch up on the Colorado River negotiations  

Listen to Jay’s first podcast appearance  

Related headlines:   

“ADWR Director Briefs UA Water Resources Research Center Conference on Colorado River Negotiations” (azwater.gov, June 2025)  

“It’s not just big alfalfa farms. La Paz residents fear groundwater grab by big cities” (Arizona Republic, June 2025)  

“Arizona wants this city to cut its groundwater use. Residents want flexibility” (Arizona Republic, May 2025)  

“Even in wet years, wells are still dry. Why replenishing California’s groundwater is painfully slow” (Cal Matters, February 2025)  

“Opinion: Will We Have to Pump the Great Lakes to California to Feed the Nation?” (The New York Times, August 2024)  

Credits:

Host: Duke Reiter

Producer and editor: Taylor Griffith

Music by: Lupus Nocte and Tellsonic

Research and support provided by: Kate Carefoot, Rae Ulrich, and Sabine Butler