NASA satellites align water trends with human use

A long satellite record turns up humans' mark on the world's water

For more than two decades, two NASA satellite pairs have tracked a signal too slow to show up in any single dry spell or flood: the gradual rise and fall of water held in soil, rivers, reservoirs, and underground aquifers. Measurements from NASA's GRACE and GRACE-FO missions reveal trends in terrestrial water storage from April 2002 to November 2025, a record long enough to separate ordinary climate swings from a steadier pattern left by human activity.

The new analysis comes from a hydrologist at NASA's Goddard Space Flight Center, working with colleagues who reprocessed that same gravity record rather than collecting new data. By combining repeated satellite passes across the full stretch of the record, the team mapped long-term water trends with five to 10 times more spatial detail than earlier analyses. The finer map traces where water storage shifted over decades; it does not show what happened in any single month or year, since the gain in spatial detail came at the cost of temporal detail.

With that sharper view, the researchers looked for places where storage trends lined up with human activity rather than climate alone. Beyond the influence of climate variability, they identified 40 regions where the changes also aligned with human activities such as irrigation, reservoir impoundment, and land-use change. These activities were significantly related to terrestrial water storage trends on every nonpolar continent except Australia. Groundwater-irrigated farmland was strongly associated with declines in terrestrial water storage across several continents, consistent with places where farmers draw on underground supplies rather than rivers or rainfall. Mary Michael O'Neill, the study's lead author, said that in four continental regions, an anthropogenic variable showed a stronger relationship with the storage trends than any climate variable did.

This is a single study; it does not establish that human activity caused every change the satellites recorded.