Upward infiltration-evaporation method to estimate soil hydraulic properties

Determination of saturated hydraulic conductivity, K-s, and the van Genuchten water retention curve theta(h) parameters is crucial in evaluating unsaturated soil water flow. The aim of this work is to present a method to estimate K-s, a and n from numerical analysis of an upward infiltration process at saturation (Cap0), with (Cap0 + h) and without (Cap0) an overpressure step (h) at the end of the wetting phase, followed by an evaporation process (Evap). The HYDRUS model as well as a brute-force search method were used for theoretical loam soil parameter estimation. The uniqueness and the accuracy of solutions from the response surfaces, K-s-n, a-n and K-s-a, were evaluated for different scenarios. Numerical experiments showed that only the Cap0 + Evap and Cap0 + h + Evap scenarios were univocally able to estimate the hydraulic properties. The method gave reliable results in sand, loam and clay-loam soils.