| The Three Gorges Reservoir has played a great role in improving the downstream flood control standards,the utilization of water resources,the water supply and shipping condition in the middle and lower reaches of the Yangtze River.However,it also has adverse effects on the water environment and water ecology,such as:the water bloom in the upper tributaries,the delay of fish spawning time,and the reduction number of fish larval in the middle and lower reaches of the Yangtze River.Fish reproduction is closely related with the flow conditions.Thus,it is urgent to study how to adjust the reservoir dispatching schemes,which can improve the flow conditions on the basis of maintaining the current reservoir function.Based on this,optimal dispatching strategy of the Three Gorges Reservoir considering fish reproduction in flood season was studied.The main contents and conclusions of the study are as follows:Firstly,the paper systematically summarized the research results of the flow conditions of fish reproduction in the middle and lower reaches of the Yangtze River and proposed the discharge requirements of the Three Gorges Reservoir during the fish reproduction period.According to the flow conditions,the Three Gorges Reservoir should plan at least one flow release with flow rising time no less than 5 days,increasing range of daily discharge from 900 to 3000 m~3/s,maximum discharge flow no more than30000 m~3/s during June 15 to July 20.Based on the discharge requirements,nine groups of ecological discharge plans of the Three Gorges Reservoir during the fish reproduction period were formed.Secondly,through the runoff characteristics and Copula correlation analysis,the inflow amount and possibility were predicted.And then the satisfaction degree of the predicted inflow was calculated according to the ecological regulations during the fish reproduction period.The advance water storage scheme was proposed for the low satisfaction degree situation.The results showed that:it's necessary to store water in advance due to low satisfaction degree of incoming flow from 2004 to 2013.And the reasonable storage water level is from 145m to 159.34m.Besides,the contradiction between advance water storage and flood prevention risk was analyzed.Thirdly,a multi-objective optimal dispatching model considering fish reproduction of Three Gorges Reservoir was built which aimed at maximum generation capacity,greatest satisfaction of ecological flow process and minimum over-discharge compared with safety discharge of downstream channels.Considered constraints in the model were water balance,relationship of water level and reservoir capacity,generation capacity of power station,maximum discharge of reservoir and power station,relationship of tail water level and water discharge,initial and final reservoir level,etc.The Genetic Algorithm combined with Pareto optimality was used to solve the model.Fourthly,choosing the typical dry,normal and wet inflow situations,the Three Gorges Reservoir dispatching process were simulated by using the model mentioned above.Dispatching schemes were proposed by taking the power generation objective,ecological objective or flood control objective into consideration.Comparing the influence of decisions on the dispatching schemes,the optimal dispatching strategies of the Three Gorges Reservoir with fish reproduction considered were proposed.In the typical dry inflow situation,more reasonable water storage scheme should be made on the basis of the characteristic of the inflow and forecasting information,by which can generate more power and improve the satisfaction of ecological flow.In the typical normal situation there is no need to store water in advance,and dispatching schemes can be decided by power generation objective or ecological objective.In the typical wet inflow situation,flood control objective should be prior adopted to avoid the significant flood risk. |
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