Spatio-temporal variations in terrestrial water storage and its controlling factors in the Eastern Qinghai-Tibet Plateau

The nature of the heterogeneity of terrestrial water storage (TWS) in the Eastern Qinghai-Tibet Plateau (EQTP) is poorly understood because of the lack of validated datasets and the complex topographical conditions. In this study, monthly GRACE Level 2 Release 6 (RL06) products were employed to characterize TWS changes between April 2002 and August 2016 in the EQTP. Based on the observations and hydrological model output, the dominant factors contributing to the changes in TWS in sub-basins, and areas of TWS decrease and increase were analyzed systematically. We concluded that the TWS in the EQTP showed a slight decreasing trend from 2002 to 2016 with obvious spatial heterogeneity. The decrease in TWS may be attributed to the increase in evapotranspiration, which explains approximately 59% of the variations. In the region where a substantial decrease in TWS was observed, the trend primarily depended on evapotranspiration, and was certainly affected by glacial ablation. Moreover, the expansion of lakes supplemented by glaciers was the main cause of TWS change in the areas where TWS increased. A decrease in TWS mainly occurred in summer and was mainly due to the increase in evapotranspiration because of warming, an increase in wind speed, and a decrease in relative humidity.