Study and application on optimization scheme of water distribution in gravity irrigation district of large-scale plain

Large-scale irrigation district is the main force of Chinese grain production and becomes the major part of water consumers on agriculture water, which makes it very important for the irrigation management to pay attention to the study on the water distribution optimization of irrigation district. According to the characteristics of large-scale plain and gravity irrigation district, this paper takes the largest irrigated area as the objective function in some type of hydrological year and uses four kinds of irrigation system which include continued irrigation, continued irrigation of main canals with hierarchical controls, rotation irrigation in segments and rotation irrigation in individuals to make scheme optimizations for wate.distribution program. Besides that this paper takes water level calculations for the main canals by using the steady non uniform flow model and gate-hole water flow mathematical model. Also it adopts experimental optimization method to carry out the scheme comparison among the opening degree of several control sluices in order to choose the optimal opening degree program. Taking Hongjin irrigation district in Jiangsu Province for example, this paper makes the simulation of scheme optimization whose result shows that the gravity irrigated area with best irrigation scheme is about 25% larger than with the worst one.