Meteorological to Hydrological Drought Propagation: the Role of Catchment Properties in Contrasting Climatic Regions

Drought is considered as a major natural hazard affecting millions globally which is characterized by an abnormal deficit of precipitation. In this study, an investigation was conducted of meteorological to hydrological drought propagation across 49 gauged and ungauged catchments in the Ethiopian Rift Valley Lakes Basin (RVLB). Standardized Streamflow Index (SSI) and Standardized Precipitation Index (SPI) were used for drought analysis. The best drought propagation period was identified using Pearson correlations between SSI-1 and SPI across different accumulation periods. Random Forest (RF) model was applied to determine the importance of catchment properties in predicting propagation periods. Further, this study was investigated the influence of different climate zones and catchment properties on drought propagation. The finding showed that SSI-1 and SPI-3 have the highest correlation across the 49 catchments, achieving a median value of 0.81. Catchments in semi-arid region showed strong propagation with a median correlation of 0.81, while humid catchments showed the lowest propagation with median correlation of 0.61. In semi-arid regions, catchments with lower values of all physical properties demonstrated a strong propagation. Similarly, in arid regions, catchments with smaller area, lower elevation, and reduced porosity showed higher propagation. In conclusion, the finding from this research helps drought mitigation by identifying key factors influencing drought propagation in gauged and ungauged catchments.