Spatiotemporal evolution patterns of groundwater storage variations in hilly area of Jiangxi Province based on downscaling analysis of GRACE data

To study the spatiotemporal characteristics of groundwater storage changes in the hilly areas of Jiangxi Province, based on the gravity recovery and climate experiment (GRACE)/GRACE-FO satellite inversion data from 2003 to 2023, a spatiotemporal evolution analysis framework of groundwater integrating downscaling reconstruction and trend identification was constructed, revealing the pattern of changes in groundwater storage anomalies (GWSA). The high-resolution reconstruction of GWSA was carried out through a deep learning model. The long-term trend component was extracted using seasonal-trend decomposition using LOESS (STL). The groundwater change trend and its significance were identified by combining the Mann-Kendall test and the Theil-Sen slope estimation method. The results show that the reconstructed high-resolution GWSA data clearly reveal the spatiotemporal evolution characteristics of groundwater storage in the hilly areas of Jiangxi Province; after STL, the sequence shows a significant long-term trend and stable seasonal fluctuations. From 2003 to 2023, the groundwater level in the entire province has risen slowly, and the overall long-term trend shows an evolution pattern of “recovery in northeastern and central regions but continuous depletion in southern regions”. Notably, Ganzhou City in southern Jiangxi exhibits a significant decline in groundwater storage, making it a representative groundwater-deficit zone. Groundwater variations exhibit compound characteristics, including regional disparities, phased evolution, and intensified high-frequency anomalies, indicating that the system remains unstable and is in a critical state vulnerable to further depletion.