Test And Simulation Of The Soil Water And Salt Movement In Da’an Irrigation Area

Da’an irrigation area is located in the eastern part of Da’an in the west of JilinProvince. By the influence of multiple factors such as the climatic, geological andhydrogeological conditions, it is easily led to soil secondary salinization during theirrigation project running if the effective irrigation and drainage are not reasonablyimplemented. For the problem of soil salinization of Da’an irrigation area, thecharacteristics of soil water and salt movement were studied by combined with indoortests and numerical simulation ways in this paper.Based on field surveying and sample collecting, we obtained the basic physical andchemical parameters of soil water and salt such as soil texture, bulk density, moisturecontent, field moisture capacity and soil water-soluble salt, and analysed the law ofthese characteristics in vertical, spatial and temporal variation. In this area, soil fractaldimension was between2.6785~2.8952, and sandy clay loam was the primaryagrotype. Soil bulk density, moisture content and field moisture capacity were large inthe northwest, central and southern areas of Da’an. Soil total soluble salts, conductivityand pH were relatively high in the north-central region of Da’an because of the serioussalinization. In most parts of this region, the soil bulk density, moisture content, fieldmoisture capacity, total soluble salts, conductivity and pH were significantly higher inApril than in September. These characteristics in profiles of saline-alkali soil and riceland of irrigation area were relatively large.Soil hydraulic property parameters of typical profile included soil watercharacteristic curve, water capacity, water diffusivity, unsaturated hydraulicconductivity and vertical infiltration rate were measured by laboratory test methods. Inorder to offering the initial parameters of soil water movement simulation, these soilhydraulic property parameters were fitted by selecting the reasonable mathematicalmodel. The results of the dynamic changes simulation test showed that part of thesalinity of soil profile was taken away with percolating water by irrigating. With theincrease of irrigation times, the salinity content could be taken away with the water was drop away. In the entire soil column, soil water balance was positive balance, and theend of water reserves compared with the initial was increased much; soil salt balancewas negative balance, the end of salt reserves compared with the initial was reduced alot, and the soil was obviously desalination state.The simulation of soil water dynamics change was proceed by using HYDRUS-1Dsoftware. Utilizing the actual measurement of soil hydraulic property parameters andmoisture content data, the simulation was identified and validated, and the test resultshowed that the numerical model could objectively reflect the basic characteristics ofthe soil water dynamics change of the soil column.Salt balance calculation in the topsoil of irrigation area showed that the soil salinityreduced104.58g/m~2. After prediction, soil salinity in the topsoil could be leachedcompletely after8years in accordance with the field irrigation with the currentirrigation quantity, and it could achieve the purpose of washing the soil salinity byirrigation.