Inversely estimation of hydraulic parameters and functions of unsaturated soil using disk infiltrometer experiment data

Analysis the flow in unsaturated soil is very complicated and is dependent on two nonlinear functions K(h) and θ(h) which are the nonlinear functions of soil hydraulic behavior. There are various methods for estimation of soil hydraulic parameters which using the infiltration test is one of them. In this study, the collected data from disk infiltrometer experiment (pressure head and cumulative water infiltration) used for estimation and optimization of soil hydraulic parameters by applying HYDRUS-2D software. The estimations done by inverse solution and Van Genuchten-Mualem model used for hydrodynamic assessing of soil sample. In addition, it is assumed that there is no hysteresis in soil sample and porous media is completely homogenous and isotropic. The silt loom soil sample with 20.7 cm in length and diameter equal to 20.7 cm selected for this experiment. The recorded data in 150 hours used as experimental observations in inverse solution of problem and the soil hydraulic functions estimated. Model ran in two discrete part, using pressure head and cumulative infiltration respectively, and results were compared. Results show that using the pressure head in depth 4 cm cannot lead to precise estimation of soil hydraulic parameters. Using the cumulative infiltration show the successiveness of this part of experiment in inversely estimation of parameters.