Study On Soil Moisture Movements And Water-saving Modes In Luanjing Irrigation Area, Inner Mongolia

This thesis is based on the research of Tackle Key Problem project-The Forecasting and Evaluation of Soil Salinization and Groundwater Environment in Luanjing Irrigation Area, Inner Mongolia. Luanjing Irrigation Area is adjacent to the Teng Ge-li Desert where evaporation is large and precipitation is small, so the area is seriously short of water and water saving irrigation method is important.The thesis analyses the impacts on the moisture transportation by some factors and simulate deep percolate situation under present irrigation modes using VS2DT software, and suggests a suitable water saving irrigation mode to spring wheat and summer com in Luanjing Area.The thesis first detailedly analyses the hydrogeological conditions and properties of unsaturated zone, then generalizes the model of simulating soil moisture transportation based on observation of soil moisture and experiments of irrigation in crop field. The boundary and initial conditions is concluded based on experimental data in the irrigation area, and the model has been proved to be practical. The parameters of the model have been adjusted according to the irrigation data. The soil moisture curve by simulating tallies with the experimental curve, then the model is suitable to be used to simulate the irrigation percolation.Net irrigation requirement is calculated in this thesis, and the reference crop evapotranspiration is calculated using the latest Penman-Monteith Method recommended by Food and Agriculture Organization of United Nations (FAO). The crop coefficient Kc of spring wheat and summer corn is calculated using the FAO-56 method. The thesis analyses the water requirement in spring wheat and summer corn's growth progresses; and finds four representative years. The thesis also analyses thenatural moisture situation and trend of net irrigation requirement in the representative years.The model is identified by field irrigation data of winter irrigation and summer first irrigation of the Hole 1 and crop evapotranspiration conditions. The sensitivity of the model to soil coefficient and crop growth coefficient is analyzed in this thesis. The soil coefficients K must be accurate for these coefficients are the crucial factors to influence the simulation results. The percolation of Hole 1 and Hole 7 is simulated under the boundary conditions and initial conditions of actual irrigation and amendatory coefficients.The water saving method of spring wheat and summer corn is suggested by combining the net irrigation amount and optimum ones got by the model. The current spring wheat and summer corn irrigation modes are assessed using the simulation results, and points out that the current irrigation modes are water-waste. In the end of the thesis a suitable water saving mode is suggested according to the simulation results.