Long-chain propagation pathways from meteorological to hydrological, agricultural and groundwater drought and their dynamics in China

Drought propagation is a complex process involving various components of water cycle. Clarifying the propagation pathways and mechanisms among multiple types of droughts is essential. However, the current drought propagation analysis mainly focuses on the relationship between two types of droughts, which highlights the urgence in studying the propagation among multiple types of droughts. To this end, this study will first develop a dynamic threshold framework to identify the propagation pathways among meteorological, hydrological, agricultural and groundwater droughts, and further investigate the risk probability, trigger threshold and their controlling factors in the long-chain drought propagation. The propagation pathways among multi-type droughts were identified as meteorological-hydrological-agricultural-groundwater drought. In the long-chain drought propagation, the spatial heterogeneity of risk probability and trigger threshold in China is significant. Among them, the risk probability triggering the next stage decreases progressively in south China, and the drought propagation is blocked. A significant upward trend exhibited in the trigger thresholds in east China, indicating that drought resistance is weakening. Temperature, aridity index and soil evaporation flux are the main drivers affecting the dynamics of trigger thresholds. This study contributes to the completeness and systematization of the propagation process of drought in the water cycle. It not only offers new insights into the process of drought propagation, but also provides scientific guidance for establishing drought early warning systems and reducing drought hazards.