龙羊峡调蓄影响下考虑历史调查洪水的非一致性洪水频率分析OA

Following the impoundment of the Longyangxia Reservoir in 1986,the mean flood peak discharge recorded at the Guide hydrological station decreased by 46.62%,indicating significant non-stationarity.However,methods for quantifying the reservoir regulation effect are still immature,leading to difficulties in ensuring the accu-racy of design floods,thereby seriously compromising both flood control safety and the multiple-purpose benefits of water resources projects.This study,taking the Longyangxia Reservoir as the research object,proposes the Available Flood Control Reservoir Index(ACRI)as a quantitative indicator of reservoir regulation effects.By integrating the Copula theory with the mechanism-based reconstruction method(Me-RS),a nonstationary flood frequency analysis was conducted,incorporating historical flood investigation data.The results show that the source-tracing reconstruc-tion method based on ACRI can accurately represent the reservoir's regulation effect on downstream flood peak regimes and effectively reconstruct the flood peak series into a stationary state.The design flood peaks derived using the Pearson Type Ⅲ distribution deviate by less than 3%from the original design values.Incorporating historical flood investigation data further improves the goodness-of-fit of the probability distribution,reducing the RMSE by 12.87%and increasing the 10,000-year design flood peak by 10.23%compared to the estimate that excludes histori-cal flood.Owing to flow regulation by the Longyangxia Reservoir,the design flood peak discharges at Guide for return periods of 50 to 10,000 years show an average reduction of 38.30%relative to the original design values.The nonsta-tionary flood frequency analysis method proposed in this study—accounting for reservoir regulation effects and inte-grating historical flood investigation data—can more accurately characterize the probability distribution of flood peaks,enhance the reliability of design flood estimation,and support flood control and water resources management at the river basin scale.