A new NASA study using satellite gravity measurements points to human activities as a major influence on how fresh water is stored across the land, the agency's Earth Observatory reported on October 20, 2026. The work draws on data from the GRACE and GRACE-FO missions spanning April 2002 to November 2025. By combining many passes over the same areas, the researchers mapped long-term water trends with five to 10 times more spatial detail than earlier analyses.

Beyond climate variability, the scientists identified 40 regions where storage changes also aligned with activities such as irrigation, reservoir impoundment and land-use change, according to the study. These activities were significantly related to storage trends on every nonpolar continent except Australia. In four continental regions, an anthropogenic variable showed a stronger relationship with storage trends than any climate variable, said lead author Mary Michael O'Neill, a hydrologist at NASA's Goddard Space Flight Center.

Groundwater-irrigated farmland was strongly associated with declines in several areas, including California's Central Valley, the southern High Plains, Chihuahua in Mexico and northern India. Elsewhere, some farming showed the opposite: in parts of sub-Saharan Africa, water tables rose where rainfed cropland expanded, despite below-average precipitation. Reservoir projects also stood out, including the Boguchany Reservoir in Russia, and the Karakum Canal in Turkmenistan registered storage gains. O'Neill said she wants to explore downstream effects of dams, diversions and irrigation, and to recover more of the temporal picture.