Research On Optimal Design Of Irrigation And Drainage Combined Channels Based On Genetic Algorithm

China’s per capita water resources is only one fourth of the world average level,and the per capita land resources account for about 40% of the world average level.With the development of China’s society and economy,China’s population is also growing.The contradiction between people and water and between people and land has become increasingly prominent.The contradiction between man and water and man-land is very prominent.Irrigation districts are important grain production base in China,which plays a very important role in China’s agricultural production and development.Most of the irrigation districts in our country’s irrigation districts were constructed in the 1960 s.Due to the economic and technical level at that time,most irrigation projects had problems such as unreasonable layout and imperfect supporting facilities.In China,the traditional irrigation and drainage ditches are generally arranged separately.Irrigation and drainage ditches and other engineering facilities occupy a high land occupation rate,while the land utilization rate and irrigation water utilization rate are low.In order to reduce the land occupation rate of irrigation and drainage project,increase the area of cultivated land in irrigation area,and improve the efficiency of water resources utilization,a new type of irrigation and drainage channels layout appear.Irrigation and drainage combined channels combine irrigation channels with drainage channels.Irrigation and drainage share a set of systems,which can reduce the project volume and land occupation.The model has been initially built in northern China,but it is not widely used in practice,and there is no perfect method for irrigation and drainage combined channels design.Therefore,it is of great significance to study the optimal design of irrigation and drainage combined channels and seek efficient and convenient optimization design methods,so as to provide a theoretical basis for the construction of irrigation and drainage combined channels in China.Through the collation and analysis of the related literatures of irrigation and drainage combined channels,this paper analyzes the cost and benefit of irrigation and drainage combined channels construction,constructs the function of benefit and cost,establishes the optimization design model with the maximum annual net benefit as the objective function from the economic point of view of irrigation districts,and puts forward the corresponding optimization algorithm.It is applied to the engineering example to verify,and compared with the design scheme of artificial experience method.The main research results are as follows:(1)This paper analyzes the cost and benefit of irrigation and drainage combined channels construction,mainly including channels engineering investment,canal building investment,annual operating costs,benefits of newly added arable land and benefits of increased production.This paper takes the annual net benefit as the objective function and the section size as the decision variable,establishes the optimization model of irrigation and drainage combined channels,and analyzes the constraints of the model solution,mainly including flow check,flow velocity,section width depth ratio,project occupation rate.(2)This paper use genetic algorithm to solve the optimization model,and determine the corresponding parameters,and use Matlab to program the optimization model.Floating point coding is adopted to avoid the redundancy of binary coding and improve the global search ability of optimization function operation.At the same time,the fitness function,initial population,genetic operator and other parameters of genetic algorithm are set and verified by an engineering example.The results show that the genetic algorithm has high efficiency and fast convergence in solving the channel optimization problem,and can quickly get the optimal design scheme of irrigation and drainage combined channels,which proves the rapid convergence of genetic algorithm and is suitable for the optimal design of irrigation and drainage combined channels.(3)The optimization model is applied to an engineering example for verification.The optimal design scheme of irrigation and drainage combined channels is obtained by using genetic algorithm,and compared with the design scheme of artificial experience method.The results show that the irrigation and drainage combined channels optimized by genetic algorithm can achieve a net benefit of 285,641 yuan,which is an increase of 2.7% compared with the design program by artificial experience method;at the same time,the genetic algorithm optimized design channels can reduce the cross-sectional area and the amount of earthwork.The annual investment cost of the research area is 114001 yuan,which is 5.1% less than that of the artificial experience method;the area of new cultivated land obtained by genetic algorithm optimization scheme has increased,and the benefit of the new cultivated land is 44155 yuan,which is 3.4% higher than that of the artificial experience method.The optimization model established in this paper is used to optimize the design of irrigation and drainage combined channels.The genetic algorithm can be used to solve the problem and the optimized design plan can be obtained efficiently and accurately,with high computational efficiency and fast convergence.It proves that the genetic algorithm has a good effect on the optimal design of irrigation and drainage combined channels.At the same time,compared with the artificial experience method,the optimal design method in this paper can reduce the cross-section area and earthwork volume of the channels,save the construction cost,increase the new cultivated land area,and make the irrigation area obtain better economic benefits.It provides a certain reference for the irrigation and drainage combined channels optimization design in the future,and is of great significance to promote the modernization of irrigation districts.