Divergent Changes in Terrestrial Water Storage Across Global Arid and Humid Basins

Understanding the terrestrial water storage changes (∆S) across global arid and humid river basins is crucial to closing the basin‐scale water balance, but still largely unclear. Here, we combine the Gravity Recovery and Climate Experiment, Global Land Data Assimilation System, and WaterGAP Global Hydrology Model products to study ∆Sin 197 global river basins with different aridity by using detrended analyses, and find that annual or multiyear mean ∆Sis small in most arid basins but relatively larger in humid basins, given the climate change and anthropogenic impacts removed. Through component analysis, we find that the soil moisture changes in drier basins contribute more to ∆Sthan those in humid basins; and the contribution of groundwater storage changes to ΔSis irrelevant to varying moisture conditions. Our results will benefit water balance studies in global river basins (e.g., global evapotranspiration estimation with a water balance approach), and have implications for water cycle studies in the context of global change. Terrestrial water storage changes in humid and arid river basins are poorly understood, but have important ecological and socioeconomic impacts. Here, we combine the Gravity Recovery and Climate Experiment, Global Land Data Assimilation System, and WaterGAP Global Hydrology Model products, which are primarily based on satellite remote sensing, to study water storage changes in 197 arid and humid basins distributed across the world. We show that water storage changes on annual or multiyear time scales are negligible in most arid basins but are not negligible in humid basins. Changes in soil moisture contribute more strongly to total water storage change in drier basins than in humid basins, due to the different soil characteristics in drier regions. Our results will benefit water balance studies in global river basins, and have implications for water cycle studies in the context of global change. Change in terrestrial water storage (TWS) remains tiny on annual and multiyear time scales, with little fluctuation, in the arid basinsChange in soil moisture makes a significantly greater contribution to change in TWS in arid basinsThe contribution of change in groundwater to change in TWS is independent of varying moisture conditions Change in terrestrial water storage (TWS) remains tiny on annual and multiyear time scales, with little fluctuation, in the arid basins Change in soil moisture makes a significantly greater contribution to change in TWS in arid basins The contribution of change in groundwater to change in TWS is independent of varying moisture conditions