2007 Volume 106 Pages 33-46
Optimum conditions for predicting unsaturated hydraulic properties using the evaporation method were investigated. Numerical simulations for evaporation from a saturated silt soil column were carried out. Sensitivities and correlations for two selected parameters of the van Genuchten-Mualem model were evaluated with the response surface in terms of the pore-water pressure heads inside the soil column. The pore-connectivity coefficient, I, which describes the tortuosity factor for the unsaturated hydraulic conductivity, had a strong negative correlation with the shape factor, a, and a positive correlation with the saturated hydraulic conductivity, Ks. It is therefore necessary to carefully select initial values for these correlated parameters. Higher potential evaporation rate, longer column, and pressure heads measured closer to the soil surface were more valuable for the parameter estimation based on the response surface analysis. The hydraulic parameters were optimized for a Fujinomori silty soil. The optimized hydraulic parameters were more reliable for longer column and pressure heads measured closer to the soil surface. Furthermore, using pressure heads at two different depths in the objective function resulted in smaller standard deviations for Ks and I than those optimized with single depth data.
