Research Of Optimized Model For Transmission And Distribution System And Comprehensive Benefit Evaluation In Northern Irrigation Areas

Large and medium-sized irrigation areas in our country have played an important role in promoting agricultural development and safeguarding food security.However,with the increasingly water stress,the implementation of the efficient utilization of water resource in irrigation areas have become a significant technical measure for the development of water-saving agriculture.The corollary reconstructions and water saving project modifications in large and medium-sized irrigation areas have been carried out in China since 2006,which makes the research on the cross section optimization of the irrigation canals and water transmission and distribution a focus.And the effects of the water saving transformation in large and medium-sized irrigation areas in China depends on the assessment of benefits resulted from the water saving transformation in large and medium-sized irrigation areas.Therefore,on the basis of plane optimization layout of irrigation canal systems,the paper discusses the water transmission and distribution systems of typical irrigation areas in different scenarios.The water-saving transformation benefits in those irrigation areas are evaluated as well so as to provide some theoretical references for water saving transformation projects in the irrigation areas.Qiqihar Jiangdong Irrigation Area,Suihua Happiness Irrigation Area,Wokenhe Irrigation Area and Farm 853 Qinghe Irrigation Area have been selected as typical irrigations areas for study in this paper.Based on three different transformation methods and combined with the actual engineering in the irrigation areas of corollary reconstruction and water saving transformation,we set up the optimization model of water transmission and distribution in irrigation areas and propose the corresponding optimization solution algorithms.Meanwhile,we conduct the assessment on the water saving transformation benefit in the irrigation areas in different scenarios.The main research achievements are as follows.(1)Four sample irrigation areas such as Heilongjiang Qiqihar Jiangdong Irrigation Area,Suihua Happiness Irrigation Area,Wokenhe Irrigation Area and Farm 853 Qinghe Irrigation Area are selected in terms of irrigation distinction scope,regional differences,natural and engineering characteristics of irrigation areas and transformation technology.And three profiles are set up in light of such indicators as irrigation styles and anti-seepage rate of canals,which include the original design,conventional irrigation and controlled irrigation.The situational assessment variables for the three profiles are also singled out.By means of the case study of the four typical irrigation areas,we analyze the plane layout characteristics of their respective canal systems.We adopt Horton River Fractal Law to study the arrangement structures of the irrigation canal systems and the canal system water utilization coefficient.The model of canal system optimization layout with the shortest channel length has been set up according to the optimal water system feature parameters.Through the analysis of operation hours,traversal ability,convergence ability and complexity of the three swarm intelligence algorithms we have selected the cat swarm algorithm for solution,which has high calculating speed,high convergence sped and high stability.The algorithm may not only apply to the solution of canal system optimization layout,but can lay a theoretical foundation for the optimizing solution of the subsequent evaluation on the irrigation canal distribution system and water-saving benefit in the irrigation areas.The qualitative improvement suggestions are also developed for other irrigation districts on the basis of the solved optimization layout of the typical irrigation canal systems.By analyzing the canal system structures,we have studied the relationship of fractal dimension,water utilization factors and irrigation areas.Our prediction on the water-saving potential for each irrigation area may provide an evaluation basis for the water-saving transformation of the irrigation areas.(2)The optimization of the cross section of an irrigation area shall be one of the key contents of water saving transformation in the area.With the popularization of water saving irrigation,the building patterns of large-section and high-flow canals have been the main restrictions to the economic development in the irrigation areas.On account of the single cross section optimization model for the existing irrigation canals,we carry out the in-depth study on the trapezoidal cross-section model on the basis of the target function of construction land occupation and wetted perimeter.In addition,we solve the equation by use of cat swarm algorithm.With the case study on the four typical irrigation areas,we analyze the indices such as water-saving benefit and engineering economy in irrigation areas transformed in three different ways.The indices analysis of water utilization coefficients and irrigation quota show that the water-saving benefit is significant in mode two and mode three transformation with the significant reduction of floor rate and canal section area.By studying the cross-section optimization in scenario mode two of the typical canal,we have analyzed the influence of canal slope factor,canal bottom width and depth of canal water on the target functions.We find out that the slope factor shows a great impact on the target function,which provides a theoretical foundation for the improvement of optimization design level of irrigation canals and the melioration of operational benefit of irrigation areas.(3)In the case of cross-section optimization of continuous irrigation canals,the concrete lining is the most common method used in water saving transformation,especially in northern irrigation areas.However,there is often unreasonable concrete lining thickness and irrational canal piecewise selection in actual transformation engineering.On the premise of assurance of safety and stability of the frost heaving of canal side slopes,the minimum thickness of concrete lining and land occupation are used as the target functions for coming up with the dynamic programming model of the continuous canal with the minimum segments.By means of the case study of the four typical irrigation areas,the construction costs of the concrete lining of the typical trunk canals in each irrigation area transformed in three different ways are analyzed respectively.The results of transformation in Mode Two and Mode Three show that the model not only saves land occupation,but reduces concrete consumption.Consequently it shows that the establishment of continuous cross-sectional optimization model should be rational,which can provide a theoretical basis for the irrigation canal design in the northern irrigation areas.Based on the canal data in Wokenhe Irrigation Area we optimize the minimum concrete lining thickness under varied temperatures.We also get the fitting of a concise formula for the lining thickness with negative temperature and design flow as the independent variables.The formula error analysis shows that the formula is precise with 10% as the maximum error.A zoom table for the minimum concrete lining thickness has been designed in order to improve the applicability of the formula.The maximum error of the zoom table is only 12% when verified by the typical canal in Jiangdong Irrigation Area,which is slightly different from the concise formula.Accordingly,the concise formula is used to calculate the transformation benefit of the single cross-section optimization of the irrigation canal.The risk-benefit ratio of canals at various levels in different scenarios in the irrigation areas is 0.60-1.08,which provides a theoretical foundation for the water-saving transformation of irrigation areas.(4)The conventional irrigation canal water distribution optimization model is mainly set up on the basis of the hypothesis of equal subordinate canal flow.However,such hypothesis can hardly be implemented in actual canal water distribution process,which limits the application of such model.Concerning this issue,we set up the canal water distribution model in Wokenhe Irrigation Area and Jiangdong Irrigation Area based on the cross section optimization of irrigation canals so as to achieve the minimum water distribution loss for the entire irrigation system.To address the problem of the unequal flow of the lower canals in the process of actual water distribution,we establish the water distribution optimization marshalling model with the minimum water distribution loss.In addition,according to the actual engineering status we carry out the case study on the two medium-sized irrigation areas of Happiness Irrigation Area and Qinghe Irrigation Area and the four typical irritation areas from the perspectives of continued irrigation.The water distribution loss of the irrigation areas in three different transformation ways has been analyzed as well.The water distribution process in various scenarios of Wokenhe Irrigation Area and Jiangdong Irrigation Area shows that the distribution process of the lower canal is reasonable with less valve regulation frequency and less discharging water and the total water distribution loss in the upper canal is also small.However,due to different planting configuration and topographic features in the irrigation areas,the water distribution process in the upper canals is not stable enough.The water distribution loss under the continuous irrigation in Qinghe Irrigation Area and Happiness Irrigation Area shows that the less the irrigation canal flow,the more the water distribution loss will be.The water distribution loss in Scenario Two of the typical irrigation area is the least.The loss is the most in Scenario One.We find out through the analysis of parameters influencing the water distribution loss that the canal length shall be the major variable affecting the water distribution loss,which can provide some reference for the water-saving transformation of irrigation areas.(5)We establish the benefit evaluation index system containing 12 indices for water saving transformation in irrigation areas by means of expert consultation,standards search and analysis of statistics of yearbook,which includes such five parts as social benefit,economic benefit,project benefit,management benefit and ecological benefit.By avoiding the selection of general indices which may result in the weakened guidance of the evaluation to the project reconstruction,the selected evaluation indices are pertinent and relevant.Based on the study on the optimization of water transmission and distribution system of the irrigation areas,we have established the benefit index system of the water saving transformation of the irrigation areas by using situational variables.We also make use of projection pursuit,support vector machine and fuzzy entropy to conduct a comprehensive benefit assessment of the irrigation areas.By studying on the self-consistent rate and the differentiating indicators we analyze the stability and reliability of the results of the three evaluations.Finally,we have reached the conclusion that Scenario Three transformation in Qinghe Irrigation Area has the optimal water-saving transformation benefit.