Study On Flood Regulation Mode And Risk Of Reservoir Under Changing Environment

Under the comprehensive influence of climate change and human activities,the water volume in the basin has been reallocated in time and space,the physical mechanism of runoff formation has changed accordingly,and the river runoff sequence and reservoir inflow flood characteristics have changed,posing new challenges to the scientific and rational operation of reservoirs.Therefore,the study on the flood control model of reservoirs under the influence of climate change and human activities can provide effective theoretical support for reservoir operation and is of great significance for improving the comprehensive benefits of reservoirs and reducing flood control risks.In order to discuss the problems and challenges brought by the change of river runoff and flood law to reservoir operation under changing environment,this paper takes Wan ’an Reservoir as an example to study the flood control mode and risk of reservoir under changing environment.Based on the sequence analysis of reservoir flood in a changing environment,the trend and variation of reservoir flood are analyzed,a reservoir simulation operation model with the goal of maximum comprehensive benefit is built based on computer programming,and the optimal solution is obtained by using artificial bee colony algorithm.The application of the research results to The Wanan reservoir is expected to improve the comprehensive operation efficiency of the reservoir,but also for other similar engineering problems to play a reference role,has a certain theoretical significance and engineering practice value.The main research contents and conclusions are as follows:(1)Mann-kendall test,Spearman rank correlation coefficient method and ordered cluster analysis were used to analyze the variation of the maximum flood peak discharge and maximum 1d,3d and 5d flood sequence of the reservoir from 1992 to 2018.The results of mann-Kendall trend test and Spearman rank correlation coefficient method both show that the annual maximum inflow flood peak discharge and the maximum flood sequence of 1d,3d and 5d in Wan ’an Reservoir have an obvious downward trend at a given confidence level(α=0.05).It is concluded that the maximum annual flood peak discharge of the reservoir has a significant downward trend,which is caused by two factors: the change of ganjiang river runoff,and the construction of upstream water conservancy projects and the influence of various water resources management in the basin where the reservoir is located.The maximum annual flood peak usually occurs in the main flood season,and the main target of reservoir operation and operation during the main flood season is flood control.Therefore,the decline of peak flood volume caused by changing environment has positive significance for reducing the flood control pressure of Wan ’an Reservoir.(2)A single flood season flood dispatching model and a variable time scale flood control and power generation combined simulation dispatching model of Wan ’an Reservoir are established to realize the integrated flood generation and power generation and flood control dispatching of the whole year or even many years.Through the analysis of the dispatching results,it is found that the actual dispatching results are better than the simulated dispatching for most of the flood dispatching and most of the generation dispatching in most years.Therefore,this study believes that reservoir operation rules usually have a certain timeliness.Under the changing environment,the operation rules are not fully adapted to the actual situation,resulting in the failure of the reservoir’s flood control function and power generation benefits to reach the expected goals.As time goes by,the operation rules need to be timely optimized according to the actual situation.(3)The flood dispatching and power generation dispatching of reservoir in flood season and non-flood season are optimized by artificial bee swarm algorithm.(1)Two indexes,peak clipping rate and flood resource utilization rate,were used to evaluate the optimization of each flood: the average peak clipping rate of optimal dispatching was greater than the actual dispatching,indicating that under the changing environment,the main optimization space of flood dispatching in flood season lies in peak clipping rate.When the flood occurs in non-flood season,the utilization rate of flood resources will decrease due to the small flood storage capacity.(2)Two indexes of water utilization rate and power generation of the reservoir are used to evaluate the optimization results of power generation operation in non-flood season: under the same situation of water utilization rate of the reservoir,the annual average power generation of optimal operation is greater than the actual operation.The main reason is that optimal dispatching can meet the requirements of shipping and irrigation while maintaining a high power generation head to maximize the power generation benefits.In conclusion,the optimal scheduling scheme is feasible.Under the changing environment,the optimal direction of flood control operation is peak clipping rate and utilization rate of flood resources,while the optimal direction of power generation operation is water utilization rate and electricity generation of reservoirs.(4)The risk rate of flood control in main flood season under conventional dispatching rules(single index and double index)is calculated and compared.The current flood control rules have basically played a good role in flood control of reservoirs,but there are still incomplete utilization of flood control storage capacity.After increasing the reservoir water level as the second discriminant index in the water storage peak clipping stage,it can be seen from the maximum discharge distribution that the risk rate of flood control decreases obviously.In a changing environment,the single index of scheduling rules need to be improved,on the basis of the index will flow as more index(water level,rainfall,etc.),and even the forecast information into consideration,can better determine the reservoir flood control situation,make a scientific decision,reducing the flood control capacity of using incomplete resulting in outbound maximum flow is too big,to alleviate downstream flood control pressure have obvious effect.