Finite Element Modeling of Soil Water Movement Under Subsurface Irrigation With Porous Pipe and Its Application

In order to acquire more scientific theories and technical basis of subsurface irrigation with porous pipes for widespread use, it is very necessary to deeply study irrigation performance of the new kind of porous pipe. A two dimension soil-water movement model with boundary of the third type was built to simulate infiltration of subsurface irrigation. Finite element method (FEM) was used to solve this model. Results of tests show that precision of the model is high. Application of the model indicates that effect of subsurface irrigation is influenced evidently by pressure of water supply, initial soil-water content, penetration rate of porous pipe. With increase of water pressure, wetting range at the end of irrigation will enlarge, and average water content within the range will become higher. The higher the initial soil water content, the more inconspicuous the wetting front, and the less the total amount of infiltration. If infiltration rate of porous pipe was larger than a threshold value, a saturated zone around porous pipe would form. The threshold value is related to the initial soil water content. By increasing infiltration rate of porous pipe, effect of subsurface irrigation will be improved.