The Three Gorges Dam has weakened the drought propagation process in the Yangtze River Basin

Abstract

The propagation process from meteorological drought (MD) to hydrological drought (HD) is crucial for drought monitoring and mitigation. While it’s widely recognized that the Three Gorges Dam (TGD) and climate change have substantially altered the hydrological conditions in the Yangtze River Basin (YRB), the effects of these changes on the drought propagation process have remained unclear. Using natural runoff, observational runoff and precipitation data during 1988–2018, and employing the Run theory, Copula function, and Bayesian network model, we quantified the impacts of the TGD’s regulation and climate variability on drought propagation in the YRB. The results showed that the TGD’s regulation raised the drought propagation threshold (DPTH) and prolonged the drought propagation time (DPT) in the upper, middle, and lower reaches of the Yangtze River (URYR, MRYR, and LRYR). It consequently weakened the drought propagation process and led to a decrease in HD characteristics (duration, severity and frequency) in the YRB by −20.57 % ∼ −0.96 %, except for the severity and frequency in the LRYR. However, the effects of climate variability on DPTH and DPT were relatively complex. It led to a decrease in HD characteristics by −27.46 % ∼ −10.84 % in the URYR and MRYR, excluding the frequency in the MRYR. Conversely, it resulted in an increase of 9.87 % ∼ 42.37 % in HD characteristics in the LRYR. This study effectively underscored the crucial role of the TGD in mitigating HD events in the YRB and contributed valuable insights into understanding how human activities and climate variability interacted in shaping drought propagation process.