Suitability of models for the estimation of soil hydraulic parameters

Abstract

This paper deals with the applicability and validation of three predictive models for the estimation of soil hydraulic parameters (soil water characteristic and unsaturated hydraulic conductivity) by using routinely available soil data. Comparisons were made of the models of Campbell [Campbell, G.S., 1974. A simple model for determining unsaturated conductivity from moisture retention data. Soil Sci. 117, 311–314; Campbell, G.S., 1985. Soil Physics with BASIC. Elsevier, New York]; regression equations of Vereecken et al. [Vereecken, H., Feyen, J., Maes, J., Darius, P., 1989. Estimating the soil moisture retention characteristic from texture, bulk density, and carbon content. Soil Sci. 148, 389–403; Vereecken, H., Maes, J., Feyen, J., 1990. Estimating unsaturated hydraulic conductivity from easily measured soil properties. Soil Sci. 149, 1–12] and the model of Gregson, Hector, McGowan (GHM model) [Gregson, K., Hector, D.J., McGowan, M., 1987. A one-parameter model for the soil water characteristic. J. Soil Sci. 38, 483–486.]. The predictions of the above models were evaluated based on measured and calculated data from six German soils. Regression analysis showed that the GHM model, based on a single paired measurement of water content vs. matric head, produced noticeably better results than the other two models, which require input of textural properties of the soils. It is recommended that hydraulic parameters be estimated from paired measurements of water content vs. matric head rather than from textural properties of soils.