Assessing the impacts of natural conditions and human activities on terrestrial water storage in Loess Plateau, China

The gravity recovery and climate experiment (GRACE) has emerged as a crucial source of land water storage information in hydrological analysis and research. Numerous factors contribute to regional terrestrial water storage (TWS), resulting in a complex mechanism. In the Loess Plateau region, the continuous alteration of natural conditions and profound impact of human activities have posed a serious threat to the natural ecosystem, leading to an escalating trend of TWS reduction. Addressing the specific analysis of how natural conditions and human activities affect TWS represents a pressing issue. This study employed the residual analysis method to discern the contribution rates of natural conditions and human activities, elucidated the spatial and temporal changes associated with each factor, and ascertained their individual influence. The findings indicated that TWS on the Loess Plateau exhibited a downward trend of -4.89 mm·a^-1 from 2003 to 2017. The combined effects of climate change and human activities accounted for alterations in water resource reserves across most areas of the Loess Plateau, with human activities predominantly driving these changes. Precipitation emerged as the primary natural factor influencing TWS variations, and NDVI demonstrated a positive feedback effect on TWS at approximately 30%. Substantial spatial disparities in TWS existed within the Loess Plateau, with human activities identified as the primary cause for the decreasing trend. Vegetation restoration plays a positive role in saving water resources in the Loess Plateau to some extent, and vegetation growth exceeding the regional load will lead to water shortage.