Ancient Groundwater Reveals Future Water Risks in US Southwest
New research sheds light on the vulnerability of Southwestern aquifers, crucial water sources for millions, to climate shifts. By studying groundwater from the last ice age, scientists are gaining insights to improve future water resource planning in the face of a changing climate.
Shifting Storms and Groundwater Dynamics
During the last ice age, the Southwestern U.S. experienced heavy storms while the Pacific Northwest remained relatively dry. As global temperatures rose, these storm patterns shifted north, changing the climate of both regions. A new study in Science Advances reveals that groundwater levels reacted differently in each area during this time.
“The last ice age gives us a window to explore groundwater dynamics that might be quite relevant to future change,”
—Alan Seltzer, Associate Scientist, Woods Hole Oceanographic Institution (WHOI)
The study shows the Pacific Northwest’s groundwater stayed stable despite increased rain, yet the Southwest had significant groundwater loss. This could mean that Southwestern aquifers are more susceptible to the impacts of climate change. The United States Geological Survey states that groundwater accounts for 37% of the nation’s public water supply. (USGS, 2024)
Investigating Ancient Water Tables
To understand long-term trends, researchers analyzed fossil groundwater from 17 wells in Washington and Idaho. They used a new method developed by Seltzer to measure isotopes of xenon and krypton, noble gases sensitive to gravitational separation. The team’s analysis showed the Pacific Northwest’s groundwater levels remained remarkably stable.
Model Validation
The researchers compared ancient groundwater data with simulations from an Earth system model, which included large-scale groundwater processes. The model results matched the isotope measurements, which validated the findings. This demonstrated that even relatively simple groundwater models can capture key dynamics.
Future Implications
This research emphasizes the vulnerability of Southwestern aquifers and shows how combining paleoclimate data with modern models can improve water resource planning. The study’s insights can help direct research and adaptation efforts in regions facing water insecurity.
