Model reveals human water use impact on shifts of terrestrial water storage patterns

World-wide demands of drinking water, irrigation, livestock, domestic use, manufacturing and thermal power are satisfied by surface water and/or groundwater extraction. Although necessary for the well-being of humans and animals, as well as plant and energy production, climate change impacts on and overconsumption of our water resources lead to severe water scarcity that approximately half of the world’s population are regularly facing. Shifts in water storage patterns and water-related hazards can be observed from space by dedicated satellite missions or simulated by global hydrological models. However, quantifying the relative contribution of fundamental drivers of terrestrial water storage (TWS) changes is still a major scientific challenge, e.g., due to a lack of data or processes in models and the limited vertical and spatial resolution of satellite data sets.

Thus, in this study, we attempt to reveal the human water use impact on shifts of TWS patterns under changing climate. We compare two decades (2003-2023) of TWS changes simulated by the WaterGAP Global Hydrology Model (WGHM) while (a) disregarding and (b) considering surface water and groundwater extraction to isolate the human impact on the terrestrial water cycle. The identified patterns are compared to observations from the satellite gravity missions GRACE and GRACE-FO to better understand the individual contributions on current satellite-based continental wetting and drying trends. In addition, the relative contribution of individual water storage components to TWS is calculated, where groundwater overconsumption shows significant impacts on shifting TWS patterns. We present the largest river basins (>200.000 km²) world-wide and a country-based assessment to identify regions under acute or chronic water stress.