Spatiotemporal Changes in China's Terrestrial Water Storage From GRACE Satellites and Its Possible Drivers

Terrestrial water storage (TWS) changes are driven by internal climate variability, external natural climate change, external human-caused climate change, and human water management. Spatiotemporal patterns of TWS change and attribution can help understand the water cycle process and refine water management in a region. Here, the spatiotemporal changes in the TWS in China between 2003 and 2016 are analyzed based on three monthly mass concentration (mascon) data products from the Gravity Recovery and Climate Experiment (GRACE) satellites, and the possible drivers are investigated using multiple precipitation products, land surface models, and multisource remote sensing and socioeconomic data. Six major TWS change regions are detected, including negative trends in northwestern China, the southeastern Tibetan Plateau, and northern China and positive trends in western China, southern China, and northeastern China. Two global hydrological models, WaterGAP and PCR-GLOBWB, substantially underestimate the TWS changes relative to GRACE. Four land surface models (CLM 2.0, VIC, MOSAIC, and NOAH 3.3) from the Global Land Data Assimilation System version 2.1 show large model uncertainties in simulating the TWS trend. A statistical attribution indicates that ice melting under human-caused climate change is a driver of decreasing TWS in northwestern China and the southeastern Tibetan Plateau that cannot be ignored, while human water use is largely responsible for groundwater depletion in northern China. The increasing TWS in southern China and northeastern China is likely caused by precipitation increases, and the increasing TWS in western China is probably a result of precipitation increases and water supplementation from ice melting.