Regional Characteristics and Impact Factors of Change in Terrestrial Water Storage in Northwestern China From 2002 to 2020

This article characterized the linear trends and interannual signals of terrestrial water storage (TWS) and meteorological variables including precipitation (P) and evapotranspiration (ET) over the arid Northwestern China (NWC). The relative impaction of P, ET, and human water utilization (HU) on TWS variation among the 10 watersheds of NWC (i.e., 5 watersheds in Xinjiang, 3 watersheds in Hexi Corridor, and 2 watersheds in Qinghai) were then investigated. The result indicated that groundwater storage (GWS) was the main contributor to the TWS variation and matched well with TWS in spatial features or watershed-scale variations. The entire NWC presented growth trends for P (0.05 cm/year) and ET (0.22 cm/year) and decline trends for TWS (-0.19 cm/year) and GWS (-0.20 cm/year). The watersheds in Qinghai province where mainly affected by natural factors showed the increasing TWS/GWS trend. The watersheds in Xinjiang and Hexi Corridor, which had strong impact from human activities generally showed the declining TWS/GWS trends, but Xinjiang showed more intensive declining trend than Hexi Corridor. The analysis of HU indicated that water sustainable management and water-saving technologies had effectively kept down the tendency of TWS/GWS declining in the watersheds in Hexi Corridor, however, they were not sufficient to address the water shortage caused by farmland expansion, slight P growth, and high ET growth in Xinjiang. Groundwater use, as the main source to compensate for the increase in HU (especially agricultural water use), exacerbated TWS/GWS loss in Xinjiang. This article provides valuable information for the water management over the arid NWC.