Drought propagation mechanisms and spatial heterogeneity in the Yellow River Basin based on convergent cross mapping and the geographical detector method

Study region The Yellow River Basin. Study focus Drought propagation, as a key process in the hydrological cycle, exhibits significant nonlinearity and spatial heterogeneity. Based on meteorological and runoff data from 1980 to 2018, the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Runoff Index (SRI) were constructed. The Convergent Cross Mapping (CCM) method was employed to identify the causal relationships and dominant propagation timescales between meteorological and hydrological droughts. Moran’s I was further applied to reveal the spatial clustering patterns of drought propagation characteristics. Finally, the optimal parameter-based geographical detector (OPGD) model was used to quantitatively analyze the driving factors and their interaction effects. New hydrological insights for the region Meteorological drought exerts a significant causal influence on hydrological drought. Propagation intensity increases from upstream to downstream, with an average dominant propagation timescale of about 7.7 months, mainly at the 10–12 month timescale. Both propagation intensity and timescale show significant positive spatial autocorrelation with clustered high-value areas. Precipitation and potential evapotranspiration are the dominate explanatory factors, while NDVI and slope play important regulatory roles, and the explanatory power of HFI (Human Footprint Index) becomes more pronounced in downstream regions. Factor interactions are stronger than individual-factor effects, indicating joint control by climate and land-surface conditions. This study reveals drought propagation mechanisms from a “causality-space-drivers” perspective, providing a basis for drought risk assessment and water resources management.