Quantifying the 2022 drought and spatiotemporal evolution of TWSA in the Dongting Lake Basin over the past two decades

Extreme hydrological events such as droughts and floods have been increasingly influenced by abnormal atmospheric disturbances caused by human activity and global warming. The Dongting Lake Basin (DLB) has experienced challenging circumstances over the past 20 years due to complex climatic variations, leading to extreme flooding and drought. This study aims to investigate the spatiotemporal variation in terrestrial water storage anomalies (TWSA) over the DLB using data from the GRACE/GRACE-FO and GLDAS spanning the latest two decades. A significant decline trend in TWSA is unveiled from July 2019 to May 2023, with the rate of change determined as −1.94 cm/year and −1.99 cm/year based on the GRACE/GRACE-FO and GLDAS, respectively. The GRACE- Drought Severity Index (DSI) is employed to identify and evaluate the severity and spatiotemporal evolution of the 2022 drought event in the DLB. The results accurately capture the drought event, which began in July 2022 and continued until March 2023, with the most severe conditions occurring in October 2022, when the GRACE-DSI value stood at −2.06 and the TWSA decreased by 15.24 cm and 33.51 cm relative to the same month in 2021 and 2020, respectively. Additionally, the daily water level variation at the Chenglingji hydrological gauging station in 2022 broke previous records, reaching a minimum of only 19 m. Comparing the 2022 drought event with the drought events in 2006 and 2011, the impact of drought on vegetation growth conditions was relatively small, but there was still significant vegetation degradation across the DLB.