Study On Some Related Techniques And Methods In Planning And Design Of The Rehabilitation And Water-saving Reform Projects In Large-sized Irrigation Districts

China has 434 large-sized irrigation districts, which not only is the backbone of China's agriculture irrigation and a important production base of commodity grain, cotton and oil, but also has a very important position and role in agriculture and rural economic development and ecological environment improvement. In order to improve the situation of irrigation engineering and management, contain irrigation efficiency attenuation, and improve irrigation water use efficiency and agricultural comprehensive productivity, the country launched a " rehabilitation and water-saving reform planning in national large-sized irrigation districts from 1998 " project. As the arduous task of rehabilitation and water-saving reform projects in large-sized irrigation districs in future, the research on related techniques and methods is extremely important.Therefore, the paper has done following works:(1) This paper proposes an optimization design method for general canal cross section and rotation canals and distribution system. The Paper During the rehabilitation and water-saving reform in large-sized irrigation districs, the cost of irrigation canal systems accounts for a large proportion of the total investment, especially the canal excavation and lining costs greatly , therefore, whether its design is scientific impacts the water resources use efficiency and the play of the irrigation and drainage engineering in agricultural production. In the current irrigation districs rehabilitation and and water-saving reform, the determination of parameters of canal profile and cross section , especially the longitudinal slope, has important significance, also has important economic value in irrigation area management after the reform completion. Based on GA, this paper proposes an optimization design model and solution method for general canal cross section and distribution canals profile and cross section, which takes the minimum engineering quantity as objective function and considers the constraints of non-scouring, non-silting and initial and ending water level; as for the optimal design of the profile and cross section of the main delivery and distribution canal, according to the common section form in irrigation districts reform, this paper first proposes a dynamic programming model for two-stage backbone water delivery and distribution system, which takes the minimum engineering quantity as objective function and considers the minimum water level connection and level constrains of the trunk and branch canals flow division.(2) The paper first constructs a quantities estimation model based on the BP neural network. According to"national large-sized irrigation districs rehabilitation and water-saving reform planning(2009~2020)", there is an investment of nearly 120 billion to be implemented until 2020. For the sake of arranging the invested funds scientifically, it is quite important to estimate the investment of building projects in irirgation area. As for water conservancy cost estimation, the project estimate appraisement method is usually adopted in our country. The method firstly estimates the quantities in accordance with the quantities of similar constructed projects, while considers the concrete conditions of the planning building engineering, secondly estimates the value quantity by different unit price and then compiles the estimation, thus obtains the investment estimation. The key problem of the method is to estimates the quantities of the planning building engineering. Through analyzing the main factors that influence the quantities of all types of building projects in irirgation areas, the papar establishes the main projects classification database including the major technical parameters, main quantities and the quantity of main materials, then first constructs a quantities estimation model based on the BP neural network, which has filled in the black of building cost estimation method in the planning stage and has a stronger application value.(3)The paper first constructs a dynamic programming model of the layout adjustment optimization of irrigation pumping station group, and firstly puts forward a dimensionality reduction method for the dynamic programming model. During the rehabilitation and water-saving reform in large-sized irrigation districts, as the water level in the main diversion channel (river) is usually low, farmland irrigation depends on the small irrigation pumping stations along the two sides of the main canal. In irrigation peak season, that the capacity of the stations is close to or greater than the transfer capacity of the canals causes a sharp level drop and ecological deterioration in the rivers sometimes.According to the characteristics of the irrigation pumping station group in irrigation districts, the paper presents a dynamic programming model of the layout adjustment optimization of irrigation pumping station group for the first time. The dynamic programming model takes the minimum energy consumption as objective function and considers the irrigation diversion demand and ecological requirement, and provides scientific basis for irrigation pumping station group layout optimization and irirgation canals planning adjustment. In view of the the characteristics of the dynamic programming model of the layout adjustment optimization of irrigation pumping station group, this paper firstly puts forward a dimensionality reduction method for the dynamic programming model with coupling constraint with clear feasible region, which enriches the theory of dynamic programming optimization.(4)In order to improve the work efficiency, this paper first uses "VB and MapX" to develop a computer aided design system based on GIS. Using object-oriented programming method and taking Microsoft Visual Basic 6.0 as the development platform, the cad system realizes the cross-platform integration of various softwares (Visual Basic 6.0, MapX control, Microsoft Access, etc.) by the way of man-machine conversation. This system can help the planners to carry out the whole planning and design process of the irrigation area, which includes the choice of the design typical year, crop water requirement calculation, deficit irrigation schedule and irrigation rate computation, GIS real-time planning of irrigation canal system, calculate of canal system design flow, design and optimization of profile and cross section, GIS real-time planning of drainage ditch, calculation of drainage discharge, design of drainage ditche section, GIS real-time planning of irrigation area building, estimate and economic analysis of project cost, and so on.