Analysis of the spatiotemporal variation of groundwater storage in Ordos Basin based on GRACE gravity satellite data

Groundwater is the primary source for drinking, agriculture, irrigation, industrial, and municipal uses in Ordos Basin, a regional energy and heavy chemical industrial base in China. In recent decades, groundwater levels in the basin have declined due to climate change and anthropogenic activity. Analyses of the spatiotemporal variation of groundwater storage are crucial to regional sustainability. This study conducts the analysis utilizing GRACE gravity satellite data and GLDAS model data, employing methods that include the generalized threecornered hat, Augmented Dickey-Fuller (ADF) test, and wavelet analysis to investigate the spatiotemporal variation of groundwater storage in the basin. The analysis results indicate that (1) before 2008, the climate had a significant influence on groundwater storage, with minimal impact from human activities, while after 2008, human activities have caused a noticeable decline in groundwater storage, particularly in the eastern region. (2) The eastern region of the basin experienced a decline in groundwater storage with a rate of -1.86 cm/yr, the middle region with a rate of -1.24 cm/yr, and the western region with a rate of -0.63 cm/yr. The extensive extraction of petroleum, natural gas, coal, and mineral resources in the basin has contributed to this pattern. (3) Human activities have altered the hydrological processes from precipitation infiltration, groundwater propagation, and groundwater distribution, leading to an increasingly complex groundwater system. (4) Human activities affect groundwater in the saturated zone more extensively than in the unsaturated zone. The research findings highlight that human activities are the main factor driving the variation in groundwater storage in the basin and provide crucial scientific evidence for protecting groundwater resources.