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February 20, 2026

Improving understanding of drought events in the Dongting Lake Basin: insights from GRACE and optical satellites

Key Points

This research aims to improve the understanding of drought events in the Dongting Lake Basin using innovative satellite technologies.
Utilized GRACE data to detect terrestrial water storage anomalies (TWSA) through Bayesian Three-Cornered Hat fusion method.
Analyzed drought characteristics using the GRACE-based Drought Severity Index (DSI).
Employed Mann–Kendall test and sliding T-test to identify changes in drought severity.
Identified a depletion of TWSA in the central Dongting Lake Basin post-2018 with a decline rate of −23.85 ± 6.16 mm/yr.
GRACE DSI effectively monitored drought evolution compared to traditional indices, revealing significant decreases in July 2022.
Drought severity peaked in March 2023, affecting over 90% of the basin, primarily due to reduced precipitation from August 2022 to January 2023.

Abstract

Recent decades have seen a significant escalation in drought frequency and intensity worldwide. As the second-largest freshwater lake in China and a critical component of the Yangtze River Basin ecosystem, the Dongting Lake Basin (DLB) plays a vital role in regional water security, biodiversity, and socioeconomic stability. However, traditional monitoring approaches face limitations in capturing water storage anomalies, whereas the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO) provide a transformative perspective through direct detection of terrestrial water storage anomalies (TWSA). This study integrates three GRACE TWSA solutions (from CSR, JPL, and GSFC) via the Bayesian Three-Cornered Hat (BTCH) fusion method. Results reveal that the uncertainty of BTCHEWH results is mere 17. 45 mm, which is notably lower than that of any individual original products, ranging from 26. 39 mm (GSFCM) to 45. 96 mm (JPLM). Moreover, it is revealed that there has been a critical depletion of TWSA in the central Dongting Lake Basin (DLB) post-2018 with a marked decline rate of − 23. 85 ± 6. 16 mm/yr. Compared to traditional drought indices, the GRACE-based Drought Severity Index (DSI) can more effectively monitor spatiotemporal drought evolution characteristics. Both the Mann–Kendall test and sliding T-test identify July 2022 as the abrupt change point, when the DSI significantly decreased. Specifically, the drought severity reaches the peak in March 2023, affecting over 90% of the basin, and the reduced precipitation from August 2022 to January 2023 is the main cause of the drought event. This finding is further corroborated by optical satellite-based analysis. The data show a dramatic reduction in water surface area of 1337. 87 km 2 from July to September 2022, which is highly consistent with contemporaneous precipitation patterns and drought evolution. This study can provide technical support for water resources management and drought resistance efforts in the DLB.

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