Modeling one‐dimensional infiltration into very dry soils: 2. Estimation of the soil water parameters and model predictions

Abstract

Using a water content based one‐dimensional finite difference algorithm, we model infiltration into a 6‐m‐lysimeter column containing alternating layers of air dried clay loam and sand. We use van Genuchten's equation to model the h−θ relationship and both Campbell's and Mualem's equations to model the K−θ relationship. Several sets of model parameters are estimated using data generated from various combinations of laboratory drainage experiments, laboratory measurements of saturated hydraulic conductivity, lysimeter observations of initial conditions, and lysimeter observations of water redistribution. We find that predictions of infiltration based on field redistribution data give the best agreement with the observed infiltration into the lysimeter. We also find that the use of Campbell's K−θ relationship results in closer agreement between the infiltration model predictions and the lysimeter observations than does the use of Mualem's K−θ equation. The results of this study show that infiltration model predictions for a carefully controlled field scale lysimeter are very sensitive to the field and laboratory techniques used to estimate the soil water parameters.