Recent findings from NASA’s GRACE (Gravity Recovery and Climate Experiment) and GRACE-FO (GRACE Follow-On) missions shed light on the significant impact of human activity on terrestrial water storage from April 2002 to November 2025. This research highlights areas where alterations in water movement through lakes, rivers, soil, and subsurface layers are most pronounced, emphasizing the relationship between these changes and human actions.
Mapping Human Influence
The study illustrates a detailed map that tracks shifts in terrestrial water storage over the specified period, revealing that 40 regions have experienced water storage changes directly linked to human interventions like irrigation, land use modifications, and the construction of reservoirs. These impacts were observed in every continent, with the exception of Australia, and were significant beyond natural climate variations.
Mary Michael O’Neill, a hydrologist at NASA’s Goddard Space Flight Center and the study’s lead author, noted that in four distinct continental regions, human-related factors had a more substantial correlation with water storage trends than climatic influences. Notable regions affected include California’s Central Valley and parts of northern India, where excessive groundwater extraction has led to pronounced declines in water storage.
Gravity Data Utilization
The insights in this study derive from over 20 years of satellite data that measure minute shifts in Earth’s gravity, reflecting changes in mass due to water and ice movements. The twin satellites in the GRACE missions have allowed researchers to compile comprehensive data, yielding monthly maps that reveal extensive patterns in water storage. This new analysis enhances spatial resolution significantly, enabling a clearer view of long-term trends compared to prior studies.
According to Matthew Rodell, deputy director for Earth Sciences at NASA, the refined spatial resolution has uncovered previously undetected human impacts on water storage, while also affirming that certain known trends are more pronounced than earlier analyses indicated.
Identifying Water Storage Changes
The study found that groundwater irrigation is closely related to declines in terrestrial water storage across various regions. In North America, this trend was evident in California’s Central Valley, the southern High Plains, and Chihuahua, Mexico, where persistent drought conditions have led to increased reliance on groundwater. In northern India, groundwater depletion was found to occur at a faster rate than previously understood, with glacial retreat contributing only minimally to this decline.
Conversely, other agricultural practices have shown different outcomes. In parts of sub-Saharan Africa, the expansion of rainfed crops has led to increases in water storage, as seen in areas where traditional savannas have been converted to millet cultivation. Similarly, in Maranhão, Brazil, the conversion of forests to soybean fields has resulted in favorable water storage trends due to effective water management practices.
Future Research Directions
The study also highlighted the impact of water diversion initiatives, with numerous large reservoirs being filled during the assessment period. The analysis was able to track these developments more effectively due to the enhanced resolution of the gravity measurements, identifying significant trends such as those associated with the Boguchany Reservoir in Russia.
O’Neill expressed an interest in further exploring how various water management strategies, such as damming and irrigation, affect downstream water storage and to better understand the interactions between local and broader human activities. She aims to integrate the higher-resolution data with standard monthly observations to capture a more detailed temporal picture of water trends, particularly in relation to specific events like droughts or changes in policy.
Source: NASA
