Analysis of drought propagation from meteorological to hydrological drought under the impact of a super-large reservoir

Hanjiang River basin, China The role of large reservoirs in modulating drought propagation is crucial for effective drought management and water resources planning. This study characterized hydrological drought events and their properties, using run theory, and analyzed correlations between the Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI) at multiple temporal scales. It assessed the impact of the reservoir on drought propagation, that involved translation rate, sensitivity, and improvement in drought duration and severity metrics. Additionally, it employed the copula function combined with a Bayesian network to explore changes in drought propagation thresholds. A significant alteration in hydrological drought properties following reservoir construction, with increased frequency of slight and moderate droughts but reduced severity of extreme drought events downstream, was found. The weakening correlation between SPI and SRI at shorter time scales suggested a diminished meteorological influence on hydrological droughts, particularly in midstream and downstream areas. The translation rate decreased significantly at stations closer to the Danjiangkou Reservoir. Improved metrics were effective in quantifying the degree of propagation. Additionally, the thresholds for triggering severe droughts increased. These findings underscore the role of reservoirs in enhancing regional drought resilience, while altering natural drought propagation patterns, providing valuable insights for improving drought prediction and developing adaptive water resources management strategies in the face of climate change. • Improved metrics are proposed to characterize drought propagation. • Thresholds for drought propagation are identified using a conditional copula-based method. • Impacts of a super-large reservoir on drought propagation is evaluated through comparative analysis.