High-Resolution Groundwater Map Reveals Extent of U.S. Underground Water Resources
Researchers have produced the most detailed estimate to date of groundwater across the contiguous United States, offering new insight into the volume, depth, and distribution of underground freshwater resources. The map represents a major advancement in groundwater science and water resource management.
Groundwater constitutes the majority of Earth’s freshwater, with only a small fraction visible in surface features such as rivers and lakes. Despite its importance for drinking water, agriculture, and ecosystems, estimating groundwater quantity and depth has historically been difficult due to limited direct observations.
The new study estimates that approximately 306,500 cubic kilometers of groundwater exist beneath the contiguous United States. This volume exceeds the combined water content of the Great Lakes by more than an order of magnitude and is several times greater than the annual global river discharge.
Methodology and Data Sources
Previous groundwater estimates relied heavily on well data, which provide localized measurements but are unevenly distributed and limited in spatial coverage. Earlier modeling approaches typically operated at coarse resolutions, ranging from one kilometer to hundreds of kilometers, restricting their usefulness for local and regional analysis.
The new map was developed using machine learning techniques applied to nearly one million groundwater measurements collected between 1895 and 2023. The model also incorporated climate variables such as precipitation and temperature, along with soil and land-surface characteristics. This approach allowed researchers to generate groundwater estimates at a spatial resolution of approximately 30 meters.
By integrating large volumes of observational data, the model accounts for both natural hydrological processes and the cumulative effects of human groundwater use.
Key Findings
The analysis shows that approximately 40% of the contiguous United States has a water table depth of less than 10 meters. This shallow groundwater zone is significant because it directly interacts with vegetation, surface water, and soil processes, influencing agriculture, ecosystems, and land management decisions.
Groundwater depth varies widely across regions, ranging from near-surface levels in some areas to depths exceeding hundreds of meters in others.
Implications
The high-resolution groundwater map provides a valuable tool for water managers, policymakers, and researchers. It can support more precise groundwater regulation, improve irrigation planning, enhance drought preparedness, and inform land-use decisions.
The dataset also improves understanding of groundwater availability in the context of climate change, population growth, and increasing water demand.
Conclusion
This new groundwater map represents a significant step forward in quantifying and visualizing underground freshwater resources in the United States. By providing detailed, nationwide estimates of groundwater volume and depth, the research supports more informed decision-making and long-term water sustainability planning.
This article is informed by existing research and reporting, including “Ma, Y., Condon, L.E., Koch, J. et al. High resolution US water table depth estimates reveal quantity of accessible groundwater. Commun Earth Environ 7, 45 (2026).”
