Spatio-Temporal Changes of Terrestrial Water Storage in Five Provinces of Northwest China from 2002 to 2022 and Their Driving Factors

This study aims to explore the spatio-temporal changes in terrestrial water storage (TWS) in the five provinces of Northwest China and to assess the influences of various driving factors on the changes in TWS. Based on the Gravity Recovery and Climate Experiment (GRACE) satellite data of the five provinces from April 2002 to December 2022, combined with datasets of various driving factors (precipitation, evapotranspiration, runoff, and anthropogenic water use) from 1980 to 2022, a trend analysis was conducted using Sen’s slope method and Mann–Kendall (M-K) tests to characterize the spatial–temporal changes in TWS. The water balance method and quantification of contribution rates were used to analyze the spatio-temporal response of the change in TWS to driving factors and the contributions of driving factors thereto. The results showed that the eastern part of the Xinjiang Uygur Autonomous Region and the northern parts of Shaanxi Province and Ningxia Hui Autonomous Region belonged to the decreasing centers of TWS, while the northern part of the Qinghai–Tibet Plateau belonged to the enriching center of TWS, with a decreasing trend at a rate of 2.86 mm/yr. Precipitation contributed positively to the change in TWS and had a high spatio-temporal response, while the other driving factors (evapotranspiration, runoff, and anthropogenic water use) all contributed negatively to certain extents. The contribution rates of precipitation, evapotranspiration, runoff, and anthropogenic water use were 0.363, −0.265, −0.258 and −0.115, respectively. The results are helpful for the scientific planning and management of water resources in Northwest China.