Estimating terrestrial water storage changes in the Tarim River Basin using GRACE data

Terrestrial water storage (TWS) plays a fundamental role in the arid Tarim River Basin, which is mainly fed by glacier and snow melt water. However, the significant scarcity of ground-based observations, especially in the high-altitude mountain areas, limits our understanding of TWS changes in this region. In this study, TWS variations in the Tarim River Basin were estimated using monthly GRACE Level 2 Release 5 (RL05) products from 2002 to August 2015. The GRACE results were validated against outputs of Global Land Data Assimilation System (GLDAS) including spatial and temporal correlation analysis. The correlation between the regional TWS time-series of GRACE and GLDAS is 0.7777. It was found that GRACE TWS shows a slightly decreasing trend of -1.4069 +/- 0.5060 mm yr(-1) in the entire Tarim River Basin during the study period and a significant spatial difference over the study area. An apparent decreasing trend in Tien Shan and the Taklamakan Desert, and a significant increasing trend in the Kunlun Mountains and eastern Pamirs Plateau were also detected. Moreover, seasonal analysis of regional TWS time-series, precipitation and the 0 degrees C isotherm height in summer showed that detrended TWS variations were consistent with precipitation while long-term trends of TWS were contrary to that of the 0 degrees C isotherm height in summer. It implied that the interannual TWS variations were dominated by precipitation and the long-term trend of TWS changes was affected by changes of the 0 degrees C isotherm height in summer. This information could enrich our knowledge about water storage changes, including glacier mass balance and groundwater, and its response to climate change in this vast but sparse in-situ measurements area.