| Flooding is one of the most devastating,widespread and frequent natural disaster facing human societies.With the continuous global climate change,the intensity,frequency and severity of flood have shown an increase tendency.Therefore,flood control under the global climate change is one of the major challenges and tough topics for the wold,especially the areas with serious flooding.However,the stationarity or consistency of hydrological sequence has been destroyed due to the climate change,thus leading to the inapplicability of traditional hydrological frequency analysis method based on consistency assumption.Furthermore,the construction of multi-reservoir not only increases the complexity of the design floods calculation,but also put forward higher request to the design of flood limited water levrls of multi-reservoir system,namely,maximization of the system flood control benefits and system economical benefits simultaneously.Therefore,this paper focuses on the design of floods and flood limited water levrls of multi-reservoir system in a changing environment.First,a design floods calculation method for multi-reservoir system was proposed considering the inconsistency of hydrological sequences and the regional composition characteristics of floods simultaneously.Second,a joint optimization design method of flood limited water levrls of multi-reservoir system based on the calculated design floods.This research can improve the comprehensive benefits and water utilization efficiency,as well as provide theoretical basis and technical support to the joint flood control planning of multi-reservoir system in a changing environment.Moreover,this paper also focues on the real-time flood control risk of reservoir.A method for calculating the frequency curve of reservoir capacity and real-time flood control risk was presented,which is designed to provide a basis for reservoir flood control operation.The main research contents and results are as follows:(1)The hydrological variation diagnosis system and the theory of decomposition and composition in time series analysis were used to conduct alteration diagnosis and non-stationary frequency analysis of flood sequences in the upper Han River,respectively.The results show that the maximum annual flood peak series of Ankang,Shiquan,and interval basin jump down in 1985,1990,and 1987,respectively.Moreover,the new design flood peak flow of Ankang is larger than the original design value when the flood return period is 5 or 20,while that is less than the original design value when the flood return period exceeds 100.(2)Both the Copula-based method and regional composition method were applied to analyze the flood regional composition rules and derive the design floods of cascade reservoirs.the results show that the flood of Shiquan accounts for a major proportion in the typical composition,equivalent frequency regional composition 1,and conditional expectation regional romposition 1,which is good for flood control of the downstream reservoir.On the contrary,the flood of interval basin accounts for a major proportion in the most likely regional composition,equivalent frequency regional composition 2,and conditional expectation regional romposition 2,which is adverse to flood control of the downstream reservoir.(3)The multi-objective optimization model of reservoir flood limited water level considering flood control and water storage was set up and solved by multi-objective cuckoo search algorithm(MOCS).The model is designed to determine the flood limited water level and the corresponding flood control rules of Ankang reservoir.The results show that the upper flood limited water level is 322.67m,which is lower than the original design value.The water level parameters of flood control rules are respectively 326.22m and 329.42m,which are higher than the original design values.Moreover,considering the change of the design floods,it is necessary to share the flood control task through joint operation of cascade reservoirs.In this manner,the flood limited water level of Ankang reservoir can be raised to some extent,thus increasing the overall benefits of the multi-reservoir system.(4)The joint optimization model of flood limited water levels was established based on the joint flood control operation of cascade reservoirs and soved by MOCS algorithm.The model is designed to determine the flood limited water levels and the corresponding flood control rules of the Shiquan and Ankang cascade reservoirs,as well as the differences of flood regional compositions to the flood control.The results show that the Shiquan reservoir can storage a part of flood water and decrease the flood volume of the Ankang reservoir when the the flood return period is less than 20,while reduce the flood peak flow of the Ankang reservoir when the the flood return period exceeds 100.Moreover,the joint flood control operation of cascade reservoirs can raise the flood limited water level and lower the maximum water level of Ankang reservoir for different flood frequencies.In addition,there is a little difference among the flood control operation processes of Ankang reservoir under different flood regional compositions when the flood return period is less than 20.Conversely,there is a distinct difference among those when the the flood return period exceeds 100.(5)The reservoir real-time flood control risk analysis model based on the joint flood control operation of cascade reservoirs was built to determine the frequency curve of reservoir capacity and real-time flood control risk.The results show that the flood storage capacity of Longyangxia reservoir decreases gradually with the shortening of scheduling period.Moreover,there is a little difference between the flood storage capacity of Longyangxia reservoir on July 1 and August 1,while that in September is significantly reduced.Similarly,there is a little difference between the real-time flood control risk of Longyangxia reservoir on July 1 and August 1,while that in September is significantly reduced. |
PDF Full Text Request