Identification of source regions of the spatial drought propagation and assessment of their drought characteristics

With extreme droughts intensifying, investigating drought propagation is critical for damage mitigation. This study identified spatial propagation by aggregating meteorological drought onset times and characterized source and sink regions using Propagation Potential (PP). By estimating the Potential Influence of Source Region (PISR), we verified how droughts originating elsewhere affect specific areas. Accounting for spatial autocorrelation, we identified homogeneous clusters with significant propagation intensity. Source and sink regions accounted for approximately 86% and 14% of all basins, respectively. Notably, in 95% of the source regions, over half of the drought events were propagated from other source regions, highlighting their dual role in both absorbing and propagating drought events. To assess their impacts on drought characteristics, a bivariate frequency analysis using a copula model was performed on these clusters. For given severity and duration thresholds, source clusters exhibited return periods within 2 years, whereas sink clusters extended up to 47 years. This divergence was most pronounced in the NRB (1.75 years for sources vs. 47.42 years for sinks), demonstrating that source regions are substantially more vulnerable to drought than sink regions.