Spatiotemporal variation analysis of groundwater storage in the southeastern mountainous region of China based on GRACE data

The southeastern mountainous (SEM) region of China has experienced significant fluctuations in groundwater levels since the early 21st century. Monitoring groundwater storage (GWS) dynamics and analyzing its spatiotemporal distribution are crucial for the sustainable management of water resources. This study constructs a groundwater storage anomaly (GWSA) dataset for the SEM region of China from 2003 to 2019 using GRACE satellite data released by CSR, combined with multiple auxiliary datasets. Methods such as the Mann-Kendall test, improved ridge regression, and wavelet analysis were employed to assess the spatiotemporal variation of GWS across the entire basin. The results indicate that the overall GWSA in the basin exhibited a slow increase until 2016, followed by a rapid decline, likely driven by human activities. The estimated increase rate was approximately 0.383 cm/yr, whereas the decline rate reached −1.117 cm/yr. In the southern hilly areas, variations in soil moisture storage were primarily influenced by precipitation, while in more complex terrains, groundwater consumption played a more dominant role in shaping GWSA trends. In highly urbanized regions, water use for domestic, environmental, and infrastructure purposes was the primary driver of GWS changes. Furthermore, the correlation between GWSA and the Oceanic Niño Index (ONI) suggests that climate change exerts a significant influence on groundwater dynamics in coastal areas over long periods (>2 years), while its impact is relatively weaker in inland regions.