Spatiotemporal evolution and meteorological triggering conditions of hydrological drought in the Hun River basin, NE China

Abstract

Abstract. The change of climate and environmental conditions has obviously affected the evolution and propagation of drought in river basins. The Hun River basin (HRB) is a region seriously troubled by drought in China, so it is particularly urgent to evaluate the evolution of hydrological drought and investigate the threshold of triggering hydrological drought in the HRB. In this study, the standardized runoff index (SRI) was applied to reveal the evolution characteristics of hydrological drought. Meanwhile, based on drought duration and severity identified by the run theory, the copula function with the highest goodness of fit was selected to calculate the return period of hydrological drought. Furthermore, the propagation time from meteorological to hydrological drought was determined by calculating the Pearson correlation coefficients between 1-month SRI and multi-timescale standardized precipitation index (SPI). Finally, based on the improvement of the drought propagation model, the drought propagation thresholds for triggering different scenarios of hydrological drought and its potential influence factors were investigated. The results show that (1) the hydrological drought showed a gradually strengthened trend from downstream to upstream of the HRB from 1967 to 2019; (2) downstream of the HRB were districts vulnerable to hydrological drought with longer drought duration and higher severity; (3) the most severe drought with drought duration of 23 months and severity of 28.7 had corresponding return periods that exceed the thresholds of both duration and severity of 371 and 89 years, respectively; (4) the propagation time from meteorological to hydrological drought downstream of reservoir has been significantly prolonged; and (5) the drought propagation threshold downstream of the HRB was remarkably higher than that upstream in all drought scenarios. Additionally, midstream showed the highest drought propagation threshold at moderate and severe drought scenarios, while downstream showed the highest drought propagation threshold in the extreme drought scenario.