Assessing the impact of agriculture, coal mining, and ecological restoration on

Global water demand is projected to rise by about 1 % annually, driven by population growth and socio–economic development (Boretti and Rosa, 2019). Meanwhile, climate change further exacerbates water supply uncertainty, increasing water resource stress (Kraaijenbrink et al., 2017; Li et al., 2022). Therefore, achieving sustainable water resource management in the 21st century is crucial (Shen et al., 2022), especially in severely water scarce regions that over a quarter of the global population resides (Uhlenbrook and Connor, 2019). Terrestrial water storage (TWS), encompassing groundwater, soil moisture, lakes, rivers, reservoirs, glaciers, and snow, emerges as a crucial indicator for assessing water resource utilization (Getirana et al., 2017; Meng et al., 2019). The decreasing trends of TWS are most notable and obvious in drylands (Chang et al., 2020; Rodell et al., 2018), posing a risk to freshwater availability and food supplies (Shen et al., 2022). While large–scale ecological restoration projects (ERPs) have successfully curb ecological degradation in drylands (Jiang et al., 2021; Shao et al., 2019), they also increased evapotranspiration (ET) and reduced runoff in water–limited regions (Liang et al., 2020; Zhang et al., 2023b). Restoring ecosystems and ensuring food security become urgent priorities in vulnerable drylands. Thus, there is an urgent need to understand the changes in water storage, which is critical for achieving sustainable water management that effectively balances ecosystems and socio–economic systems.

The Mu Us Sandyland (MUS) is located in a transitional zone between the Loess Plateau and the Ordos Plateau, characterized by a delicate and vulnerable ecological environment (Yan et al., 2015). Since the 1990s, the Chinese government has consistently implemented massive ERPs in this region, such as the Grain for Green Project (GFGP), grazing prohibition, the fourth phase of the Three–North Shelterbelt Project, and so on (Zhang and Wu, 2020). Over the past 30 years, there has been an increasing trend in overall vegetation coverage (Gao et al., 2022), contributing to widespread dune stabilization, enhanced carbon sequestration, and reduced soil erosion (Gou et al., 2022; Liu et al., 2022a; Yan et al., 2015). Nevertheless, strong vegetation greening has also changed water cycle components and total water resources. Zhao et al. (2021) quantified the TWS consumption rate caused by large–scale ERPs in the MUS is −16.6 ± 5.0 mm yr⁻¹. Zhang and Wu (2020) proposed that an elevated vegetation density decreases groundwater storage (GWS) in the MUS. Luan et al. (2023) examined the correlation between surface water fluxes (such as precipitation, ET, and runoff) and observed groundwater level fluctuations in the MUS from 2001 to 2020, employing the water balance theory. Luan et al. (2023) found that the decrease in groundwater levels reversed in 2011. These studies deepen the understanding of the impact of ecological restoration on water resources in the MUS, but the impact of human activities has not been considered.

In recent years, the MUS has become a pivotal coal transportation hub in China, driven by urbanization and coal resource exploitation (Liu et al., 2022b; Yang et al., 2017). Additionally, it reveals tremendous agricultural development potential, primarily due to its higher precipitation and groundwater resources compared to other sandy regions in China (Guo et al., 2021; Liu et al., 2022a). The “Requisition–Compensation Balance” policy of the Chinese government, which seeks to offset the loss of cropland due to urbanization by reclaiming cropland in other regions to guarantee food security (Chen et al., 2019), has driven extensive cropland reclamation in the MUS (Shi et al., 2019). However, the increasing water demand for agriculture and industry has accelerated the consumption of groundwater resources, further intensifying the competition for water resources between natural and socio–economic systems (Feng et al., 2016; Liang et al., 2019). The influence of socio–economic activities on TWS and GWS decline remain unclear. Therefore, it is essential to quantitatively analyze these factors for accurately guiding future water resource management.

Traditional methods for monitoring groundwater depend on groundwater wells, which have limitations in representing regional studies and comprehensively providing a thorough understanding of the current state and changes in large–scale GWS (Rodell et al., 2018). The Gravity Recovery and Climate Experiment (GRACE) satellite provides an assessment method for changes in TWS by measuring variations in the Earth’s gravity field. Combining GRACE with hydrological models offers a highly efficient method for monitoring large–scale variations in GWS (Xie et…