Estimation of the empirical model parameters of unsaturated soils

For each flow modelling in the unsaturated soils, it is necessary to determine the retention curve and the hydraulic conductivity curve of studied soils. Some empirical models use the same parameters to describe these two hydraulic properties. For this reason, the estimation of these parameters is achieved by adjusting the experimental points to the retention curve only, which is more easily measured as compared with the hydraulic conductivity curve. In this work, we show that the adjustment of the retention curve theta (h) is not generally sufficient to describe the hydraulic conductivity curve K (theta) and the spatio-temporal variation of the moisture in the soil theta (z). The models used in this study are van Genuchten-Mualem model (1980-1976) and Brooks and Corey model (1964), for two different soils; Gault clay and Givors silt.