Characteristics of propagation from meteorological to hydrological drought under natural conditions in the Haihe River Basin of China: Time, probability, and threshold

The Haihe River Basin (HHRB), China. Understanding the propagation characteristics of droughts from meteorological to hydrological stages is crucial for effective early warning systems. However, these characteristics (time, probability, and threshold) remain unexplored under natural conditions. This study aims to fill this gap by studying the propagation characteristics of drought from the meteorological phase to the hydrological phase under natural conditions. Utilizes the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Runoff Index (SRI) to analyze meteorological and hydrological droughts in the Haihe River Basin (HHRB), China, using data from 1981 to 2018. Spearman’s rank correlation coefficient, copula probability models, and Bayesian causal frameworks are employed to investigate drought propagation characteristics. The study shows significant regional differences in the propagation time from meteorological to hydrological droughts, with shorter times in the northwest and longer times in the southeast. Additionally, the duration of droughts in spring and winter is generally longer. The drought propagation time has shown a significant increasing trend from 1981 to 2018, especially in the central and western regions. The probability of meteorological drought triggering hydrological drought increases with the severity level, and the thresholds for meteorological drought differ across various levels of hydrological drought. These findings highlight the importance of considering regional differences, seasonal variations, and the impact of climate change on drought trends in drought warning systems and water resource management. • Propagation time, probability, and threshold were fully examined. • Propagation time shows a significant increasing trend and longer in spring. • Higher probabilities triggering hydrological drought are located in the middle west. • Threshold is dominated by moderate and above levels of meteorological drought.