Identifying Groundwater Droughts and Its Recovery Based on Long-Term Groundwater Storage Simulation in Catchments Across Poyang Lake Basin

Groundwater droughts pose a significant threat to global water security, leading to critical shortages in groundwater resources and exacerbating ecological degradation. Despite the significant implications of droughts, the influence of climatic and vegetation factors on characteristics of drought recovery remains poorly understood. In this study, long-term monthly aquifer groundwater storage processes from 1983 to 2019 were estimated by employing the VIC-SIMGM model across seven sub-basins in Poyang Lake basin, with multiscale validation according to monitoring wells and GRACE data. Then, catchment groundwater droughts were identified using the standardised groundwater storage drought index. Results indicate that the 7 sub-basins experienced 15–21 groundwater droughts from 1983 to 2019, with the longest and most severe droughts occurring between 2003 and 2010 across all sub-basins. Furthermore, drought recovery times and speeds were calculated, revealing that the average recovery time ranged from 5.05 to 9.93 months, and average recovery speeds ranged from 0.14 to 0.36. The Ganjiang and Fuhe River basins experienced relatively shorter recovery times and faster recovery speeds, while the Changjiang River basin exhibited the most severe droughts with the slowest recovery process. Through correlation analysis, we evaluated the effects of climatic and vegetation factors during the recovery period—including precipitation (P), soil moisture anomalies (SMA), the climate moisture index (CMI), and NDVI—on the characteristics of drought recovery. We found that precipitation has a limited direct influence on drought recovery, while indirect surface regulation processes, particularly SMA and CMI, play a more dominant role. Higher SMA and CMI values are associated with increased recovery speeds and shorter recovery durations. In contrast, higher NDVI values are linked to prolonged recovery periods, suggesting that vigorous vegetation growth may hinder groundwater recharge. The results provide valuable information for long-term groundwater drought identification and highlight the critical role of soil moisture and climate moisture in groundwater drought recovery.