Study On Farmland Drainage Index And Optimal Planning Of Drainage Project

As the development of economy in our country, the cities extending incessantly, and the population increasing rapidly, the farmland per capital decreases continuously. According to the investigation, there is only 0.1ha per capital in China recently. The security of food supply will be threatened day by day. For there is little possible of increase of farmland area, it is a major problem faced in China that how to increase the yield of per unit area.According to the statistic, there are 87.44 million hectares middle and lower yield farmlands (MLYF) in China. Among them there are about 10.857 million hectares caused by the waterlogging, which is about 12.4% of the total MLYF. The reclamation of the MLYF is an effective way of increasing crop output per unit area so as to increase the total food production.Combining the science and technology research plan project "integrated techniques of surface and subsurface waterlogging control" supported by the Hubei Bureau of Water Resources and the program supported by the Shanghai Bureau of Water Resources, this thesis included two parts of research: the first part focused on the drainage indexes and drainage standards; the second part focused on the research of optimizing model of polder control of waterlogging and it's computation.The recent research results of the drainage indexes and drainage standards were summarized in the first chapter. The second and the third chapters focus on the research of the first problem. For that the recent existing problem of drainage indexes and drainage standards for the integrated control of surface and subsurface waterlogging, the thesis conducted the studies on all of the stages of crop growth in waterlogging in lysmeter. Through the experiments on combined controlling on surface and subsurface waterlogging of cotton in Drainage and Irrigation Experiment Station (DIES) of The Four Lake Engineering Management Bureau in Jingzhou in Hubei province for two years (2003-2004), the thesis researched on the combined controlling on surface and subsurface waterlogging indexes, and established the related crop water production functions under the waterlogging. The parameters of the water production function were determined by the experimental data, and they were the integrated sensitive indexes of the waterlogging on crop. In the same time, the sensitivities of four phases of cotton were ranked, and the sensitivities of the twofactors were also analyzed. The thesis also analyzed the relationship between the crop yield and the combined controlling of surface and subsurface water logging indexes based on the experiments of cotton and rape, and the parameters of the model were determined.The same as the research above, based on the experimental data on cotton in field condition in the DIES, the thesis established the relationship between the crop yield and the combined controlling of surface and subsurface waterlogging indexes in filed condition, and the parameters of the model were determined.As the surface and subsurface waterlogging were detached in design of drainage system recently, the third chapter theoretically proposed a new method in design of drainage system using the research contents above. This method emploied two computer models Duflow and Drainmod to simulate the water process on surface and subsurface, and achieved the combined controlling of surface and subsurface waterlogging. Then several scenarios were simulated, and the best design one was chose by maximized the ENPV. This method supplied a new way in design of drainage system.The fourth chapter emphasized on the second part. The recent research results of the optimizing model in drainage system design and their computations were summarized in the first. Then the thesis took the most important characters, the width of the sluice and the design discharge of the pumping station to research, and for the different hydraulic characters on the two factors, established a mixed optimizing model combined the simulation techniques and the optimizing technique together. It also researched on the influence of the different tide processes on the size of the sluice and the pumping station, and how to choose the right tidewater processes in drainage system design. As the restrictions are complex, the author chose the genetic algorithms to solve the problem, and made some solutions.