Three-dimensional evolution of hydrological drought and its linkage to meteorological drought in the Ganjiang River Basin, China

Study region Ganjiang River Basin (GRB), China. Study focus This study investigated the spatiotemporal evolution of hydrological drought (HD) and its relationship with meteorological drought (MD) across the GRB within a three-dimensional spatiotemporal framework. A gridded drought index dataset spanning 1961–2019 was constructed using the SWAT model and Inverse Distance Weighting interpolation. A three-dimensional drought identification framework was applied to pinpoint drought events and analyze their spatiotemporal characteristics, while the copula method was used to explore the linkage between HD and MD. New hydrological insights for the region The affected area, frequency, and severity of HD in the GRB generally decreased over time, with the most severe conditions concentrated in the middle stages of HD events; approximately 50% of events exhibited multimodal behavior. A 3-month lag was identified between MD and HD, and their durations and severities were strongly correlated: HD duration increased with MD duration, but HD severity plateaued beyond a certain MD severity threshold. The MD-HD response probability increased with increasing MD return periods, while the dominant matching characteristic changed with return periods: severity-based correspondence was more prominent at shorter return periods, whereas duration-based correspondence became more dominant at longer return periods.