A complex network perspective on spatiotemporal drought evolution in the Dongjiang River Basin, China

Study region The Dongjiang River Basin in southeast China, a critical water source region for the Pearl River Delta with a subtropical monsoon climate and frequent dry–wet transitions. Study focus Drought evolves through development, propagation, and recovery, yet few approaches unify temporal state transitions and directed spatial propagation. Using root-zone soil moisture data (1980–2025) from the GLEAM assimilation product, this study developed a complex network framework coupling a temporal state transition network with a spatial transfer entropy network to characterize complete drought life cycles. Drought life cycles were classified into five evolution modes by soil moisture change rate, with directed spatial propagation quantified via transfer entropy. MODIS-derived gross primary productivity and enhanced vegetation index provided independent ecological validation. New hydrological insights for the region Gradual processes dominated drought evolution, with slow development and quasi-stationary modes accounting for 52.5% of life-cycle time steps. A slow-drying, rapid-wetting asymmetry emerged: the median recovery rate was 1.5 times the development rate, formation decelerated, and termination shifted abruptly to rapid recovery. Spatial propagation was highly connected and weakly modular (86.2% single-step edges), with signals converging from peripheral sources toward three core sinks controlled by a few hub cells. Vegetation responses differed distinctly across the five modes, confirming their ecological relevance. These findings improve understanding of drought evolution and spatial propagation, informing drought zonation and water resources management in the basin.