Drought forecasting and severity assessment method based on characteristic waterbodies

To enhance the capability for early identification and evaluation of drought occurrence and development process, the research proposes the concept of “Characteristic Waterbodies” and classifies them into small waterbodies sensitive to drought and medium-to-large waterbodies with significant seasonal variations, exploring their application in early prediction and process assessment. For small waterbodies, a normalized small waterbody size transition index (NSWSTI) was developed based on water body size transition relationship for early drought forecasting; For medium-to-large waterbodies, a remote sensing dry-wet index (RSDWI) was proposed and combined with standardized area anomaly index (SAAI) and multi-source hydro meteorological factors to construct a comprehensive drought index. The drought events in the Poyang Lake, Dongting Lake, and Hongze Lake basins in 2022 was selected as case studies for analysis. The results show that NSWSTI respond approximately half a month earlier than observed water-level changes in the Dongting Lake and Poyang Lake basins, and also demonstrate a certain lead time relative to storage-capacity changes in the Hongze Lake basin. The comprehensive drought index can effectively reflect the development process and spatial differences of typical basin-scale drought events.