Research On Flow Regime And Ecological Operation Of Downstream Three Gorges Reservoir

Reservoir operation affects the hydrological regimes of downstream river channel and the aquatic habitats of river environment and eventually threaten river ecosystem.However,the existing reservoir operating schemes only consider the minimum ecological flow constraint,which merely consider the impact on downstream river channel after reservoir operation.Therefore,it is important to carry out the study of ecological reservoir operation.Based on summarizing the literature of ecological reservoir operation,the China's Three Gorges Reservoir(TGR)is selected as a case study,and the streamflow of Yichang,Shashi and Luoshan hydrological stations are used to analyze the hydrologic variation of reservoir downstream.Main contents and results are summarized as follows:(1)The hydrological variation of downstream TGR is analyzed.The conventional operating rules of TGR and the Multi-input Single-output Liner System model of Yichang-Shashi and Yichang-Luoshan are used to simulate the Yichang,Shashi and Luoshan runoff.The Indicators of Hydrologic Alternation(IHA)are subsequently selected to evaluate the hydrologic changes.The Multiple Linear Regressions are used to analyze the relationship between Relative Change Rate of 33 IHA indexes and ecoflow.The results show that TGR operation has changed the runoff process at Yichang,Shashi and Luoshan stations and the Relative Change Rates gradually decline with the increasing distance from TGR.Furthermore,the Correlation Coefficient between 33 IHA indicators' relative change rate of Yichang station and ecoflow is 0.81,which indicates that ecoflow can represent the main characteristics of 33 indicators of IHA and avoid the redundancy of IHA.The ecoflow index will be used as the objective function of ecological operation model in the following research.(2)The study of TGR ecological operation is carried out.Based on the Power-Assurance Multi-objective Optimization Model,which is built from the reservoir operating curves,the Pareto distribution is obtained by using NSGA-?algorithm.The results show that the mean annual power generation and assurance rate restricts mutually.The ecological factor ecoflow is then applied to build the Power-Assurance-Ecology Multi-objective Optimization Model,with the four major Chinese carps and Chinese sturgeon fish' ecological flow constraints being considered.The results show that the multiple operating solutions can provide feasible schemes for ecological reservoir operation.Lastly,ecological objectives of the multiple downstream hydrologic stations are considered to build Power-Assurance-Ecology Optimization Model.Multiple operating schemes are set in the case study.Results show that one of optimal schemes has better results,with average annual power generation and assurance rate having an increasing of 1.06%and 2.50%,respectively.Furthermore,ecological benefits of the three hydrologic stations are also improved.