Influence Of Xiaolangdi Dam On The Reproduction Of Yellow River Carp And Multiobjective Optimal Operation Of Reservoir

Dam construction not only brings great social and economic benefits to human beings,but also changes the natural circulation process of river hydrology,thus affecting the survival,reproduction and habitat environment of aquatic organisms.By analyzing the status of fish habitat,the ecological effects caused by the dam are studied,and the multi-objective operation mode of the reservoir considering both ecological protection and economic benefits is further proposed.It is of great practical significance to improve the comprehensive benefits of the reservoir and protect the ecology of the basin.The study took a section of the Yellow River from the Xiaolangdi Dam to Gaocun as the research area,and the habitat suitability model of the Yellow River carp coupled with one-dimensional hydrodynamic model was constructed.The spatial and temporal changes of the suitable habitat of the Yellow River carp before and after the construction of the Xiaolangdi dam were explored by the habitat suitability index method.At the same time,based on the spawning characteristics of the Yellow River carp,a multi-objective optimal operation model of Xiaolangdi Reservoir was constructed to meet the needs of the Yellow River carp,which provides theoretical reference and technical support for the ecological operation of Xiaolangdi Reservoir.The main conclusions are as follows:(1)Based on the topography,hydrology,and water temperature data of the lower Yellow River,a one-dimensional unsteady hydrodynamic model for the Xiaolangdi to Gaocun reach was constructed.The model was calibrated and validated using the measured flood data from hydrological stations such as Xixiayuan in 2018.The calibration and validation results were good,indicating that the model can well simulate the flow process of the lower Yellow River and meet the research needs.(2)Based on the breeding habits of Yellow River carp,a habitat model of Yellow River carp coupled with a one-dimensional hydrodynamic model was constructed.and its availability was verified based on historical spawning ground data.The model results showed that compared with that before the construction of the dam(19801990),the breeding time of the Yellow River carp was delayed after the construction of the Xiaolangdi Dam(2006-2018),the habitat suitability of the spawning reaches slightly decreased,the extent of spawning reaches decreased by 16.23%and several spawning reaches were lost entirely.After the construction of the dam,the main reason for the decrease in habitat suitability of the Yellow River carp was the decrease in water level rise and the decrease in water temperature due to the artificially controlled discharge of the Xiaolangdi Reservoir.(3)Based on the spawning suitability curve of Yellow River carp,the ecological objective function was established,and then the multi-objective optimal operation model of the reservoir considering both the power generation and the spawning demand of Yellow River carp was constructed.The NSGA-II algorithm was used to find the scheduling scheme of Xiaolangdi Reservoir in the typical normal year of the lower reaches of the Yellow River.The optimal power generation scheme and the reservoir optimal operation scheme considering power generation and spawning demand of Yellow River carp were obtained.