Sarantuya TSEDEVDORJ

A Study of Parameter Estimation for Three Infiltration Formulas Based on Hydrus1D Numerical Solution

Minjiao LU

Grasp of infiltration water into the soil, such as the determination of irrigation water in the farmland, has a close relationship with real-life problems. Generally, the soil infiltration process is expressed by using the 1D Richards equation. This equation is an expression of the vertical flow for predicting the water content and matric potential of the unsteady flow. In this study, focused on hydrostatic equilibrium state when there is a water table in the soil column. Firstly, penetration of uniform volumetric water content state is compared with hydrostatic equilibrium state. Then detailed numerical calculation with respect to the water table depth is carried out for 12 different soil types using moisture transfer analysis model, Hydrus1D. Based on those results, parameter values of three infiltration formulas: Horton (1933), Philip (1957) and Green-Ampt (1911) are estimated. Finally, those three formulas are analyzed and evaluated. As a result, it is found that the infiltration curve derived by parameter values of Philip and the Green-Ampt equation are better fit than Horton equation. Compared with numerical solution of Richards equation, it is likely that Philip equation gives the closest values. Concerned with Philip and the Green-Ampt equation, when saturated hydraulic conductivity (Ks) for coarse-grained of Loamy sand, Sandy loam is large, parameter estimation result was good. However, if Ks of fine-grained of Silty Clay, Silty clay loam is small, parameter estimation came out differently.

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