A New Method Towards More Rational Drought Propagation Characterization in Karst Regions

Abstract. Drought propagation time (T_P) and lag time (T_L) from meteorological to hydrological droughts are two important indicators for characterizing drought propagation, and thus, reasonable estimates of these indicators are conducive to improve the prediction of hydrological droughts. However, traditional quantification methods are mostly based on moving correlations of whole hydro-meteorological series, including the misinformative non-drought periods. Particularly for the karst regions, the flashy regime of rainfall-runoff relationship during non-drought periods might strongly bias the estimations of the drought propagation indicators. In this study, we propose a new method that use only the informative drought-period data to better quantify the above indicators. Moreover, we compared the effectiveness between the new and traditional methods in regions with different karstification degrees. The results revealed that: (1) hydrological drought events generally exhibited reduced frequencies, longer durations, and smaller deficit volumes than the corresponding meteorological drought events; (2) compared to conventional methods, the T_P and T_L obtained by using the new method better meet the practical requirements for monitoring more hydrological drought deficit volume, especially in karst regions; (3) the karstification degree is a key factor influencing the difference between the results obtained using the new and traditional methods, and the superiority of the new method is more pronounced with stronger karstification degrees of the region. The above results can improve our understanding of the drought propagation features in karst regions and can provide an evidence-base for precautional drought-mitigation actions.