Contrasting groundwater depletion patterns induced by anthropogenic and climate-driven factors on Alxa Plateau, northwestern China
The groundwater storage of China's Alxa Plateau (AP), one of the driest plateaus in the World, with a mixed landscape of deserts, including the Gobi, natural riparian oases and mosaic groundwater-fed irrigation areas, is vulnerable to global climate change and enhanced human activities. In this study, we revealed the temporal and spatial pattern of the changes in groundwater storage (GWS) across the AP by integrating satellite observations, hydrological modelling and ground data during the period of 2003-2016. Our results showed the GWS experienced a significant decreasing trend across the AP, while the precipitation did not significantly change. GWS continues to decrease in the center of the AP, i.e., the Badain Jaran Desert, which is likely associated with the fact of increasing evapotranspiration. The anthropogenic influences were reflect as the long-term extraction of groundwater has strongly depleted the GWS in the southeastern AP; however, in the northwestern part of the AP, groundwater depletion has been relieved due to the water diversion project with general increasing river runoff. Furthermore, based on our analysis and a broad review of the studies in other sub-regions over the AP, the possible regional flow path was proposed with particular addressing on the likely influence by anthropogenic activities. The dynamics in the GWS among the different hydrogeological units is likely interconnected through regional groundwater flow paths. Decreasing of GWS in the central AP, which would lead to reducing groundwater discharge to the northwestern AP, might further cause the groundwater depletion in the northwestern AP. Our results emphasize the tempo-spatial patterns in GWS change and the associated hydrological and ecological processes across the dry plateau. Identifying and untangling the various processes that impact on groundwater storage would allow us to develop more effective water management strategies.