The relative contributions of precipitation, evapotranspiration, and runoff to terrestrial water storage changes across 168 river basins

Abstract Changes of global terrestrial water storage (TWS) retrieved from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have been extensively evaluated in previous studies. However, natural drivers and their relative contributions to global TWS changes (TWSC) are still poorly understood. In this study, based on two global precipitation (P) datasets, three global evapotranspiration (ET) datasets, and one global runoff (R) dataset, the responses of TWSC to the three major water fluxes, P, ET, and R, were comprehensively examined for 168 river basins. In addition, by using hierarchical partitioning (HP) analysis, the corresponding relative contributions (RC) of P, ET, and R to TWSC were quantified. The results showed that for the period Jan. 2003–Dec. 2011, significant increases in terrestrial water storage anomalies (TWSA) were observed over 49 basins, whereas 42 basins presented significant decreases in TWSA. A robust positive relationship between P and TWSC was observed in low-latitude basins, but strong negative relationships of TWSC with ET and R were identified in mid- and high-latitude basins. Averaging the degree of explanation of 168 basins for all P–ET–R combinations, we found that three independent variables explained an average of 61.4% of TWSC. The corresponding RC of P, ET, and R were 42.6%, 43.2% and 4.2%, respectively. In spatial terms, a larger contribution of P to TWSC was found in low-latitude basins, and larger contributions of ET and R were identified for mid-and high-latitude basins. The findings of this study were important for improving our understanding of global TWSC responses to climate change.