Evaluating main drivers of terrestrial water storage depletion in the agro-pastoral ecotone of northern China

Abstract

With the heightened threat of declining terrestrial groundwater, determining the effects of changing environments on terrestrial water storage anomaly (TWSA) is essential for water resource management. As a critical element of the water cycle, the multi-effects of the natural and artificial factors on TWSA were still not fully understood and quantified. Using multiple high-resolution data products and the structural equation model (SEM), this study discussed how climate, vegetation, and human activities affected terrestrial water storage (TWS) in the West Liao River basin (WLRB), China, from 1990 to 2020. The results confirmed that vegetation showed a greening trend while TWS depleted at 5.93 cm/10a in the WLRB. TWS in greening areas has a negative correlation with vegetation growth. The decline in TWS is mainly dominated by precipitation and runoff variability. By influencing eco-hydrological cycle processes, climate change and human activities affect TWS through direct and indirect(by influencing NDVI) pathways. Land use change, manifested as conversion of grassland into cropland, contributed to the most decline of TWS (51.2 %). Moreover, the crop yield increasing, climate warming, and vegetation greening could lead to TWS depletion. Spatially, the overexploitation of the groundwater for irrigation to support crop production was probably the most critical cause of TWS depletion over upstream of the WLRB. Furthermore, in the West Liao Plain, the intensified vegetation greenness also led to the increasing ecosystem water demand, resulting in the decrease of TWS. This study improves our understanding of the interaction of the basinal eco-hydrological system and provides a hint that reducing groundwater extraction and implementing agriculture fallow is essential to recovering water storage and alleviating the water resource crisis in the agro-pastoral ecotone.