In many water-scarce regions of the world, the signs are obvious. Just look at the dramatically reduced Colorado River or the parched bed of the Danube. Much less striking is the global water crisis unfolding under our feet, although it is serious. This is according to a recent study published in the journal Proceedings of the National Academy of Sciences. Researchers analyzed NASA satellite data to map global trends in freshwater storage in high resolution, revealing regions where human activities, such as agricultural and urban water use, are putting terrible pressure on groundwater supplies. “The regions of greatest concern are those already recognized as being affected by water stress, where we are now seeing even greater losses than previously estimated,” Mary Michael O’Neill, an assistant research scientist at the University of Maryland and NASA’s Goddard Space Flight Center, told Earth.com. Mapping a water crisis from space While it is natural for Earth’s freshwater reserves to fluctuate, human activity has become a dominant factor in groundwater depletion. In many parts of the world, groundwater extraction for irrigation, industry and municipal uses has become a fundamental component of the water cycle, and climate change is only exacerbating this tension. “Estimates of total global freshwater withdrawal range between 3,800 and 5,000 gigatonnes per year, and unsustainable practices have resulted in widespread water shortages,” O’Neill and colleagues write in their report. “Accurately identifying and quantifying long-term anthropogenic changes in freshwater resources is critical to implementing strategies to ensure water and food security.” To that end, scientists have used data from NASA’s Gravity Recovery and Climate Experiment (GRACE) and its successor (GRACE-FO) in hundreds of studies to track changes in global freshwater supplies. These two pairs of satellites, launched in 2002 and 2018, respectively, have used precise satellite-to-satellite measurements to quantify small changes in Earth’s gravitational field that allow researchers to infer mass redistributions in the atmosphere, oceans and continents. The problem is that previous methods for analyzing GRACE and GRACE-FO data could not reliably detect changes in areas smaller than about 58,000 square miles (150,000 square kilometers). To identify exactly where freshwater depletion is most severe, the researchers behind this new study applied an innovative processing method to global, non-polar terrestrial water storage data collected between April 2002 and November 2025. This allowed them to produce a map of terrestrial water storage trends with five to ten times the spatial resolution of traditional maps. The researchers then focused on hotspots of freshwater depletion and used statistical models to investigate how climate change and human activity were related to these changes. Drying up aquifers The analysis revealed 40 regions where human activities are the main driver of decadal changes in terrestrial water storage. Indeed, anthropogenic land and water use was significantly associated with strong terrestrial water storage trends on all non-polar continents except Australia, and losses substantially exceeded gains. Regions such as the Middle East and North Africa, northern India, the western United States and southeastern Brazil were among those that suffered widespread losses. The study shows that groundwater pumping is playing an important (and previously underestimated) role. According to the researchers, previous estimates of the decline in terrestrial water storage associated with groundwater extraction were, on average, 45% lower than this new estimate. “A key conclusion of this study is that freshwater storage trends in many heavily managed basins and aquifers are sharper than previously estimated, with implications for food and water security, hydrological and climate modeling, and understanding the delicate balance of Earth system processes,” they write. The revealing findings underscore the need for better groundwater management, particularly in regions where agriculture relies heavily on groundwater sources.
