Parameter identification of solute transport models for unsaturated soils

Abstract

In models of unsaturated flow and solute transport, parametric relationships may be used to define material properties, namely the soil moisture characteristic, unsaturated conductivity function and the hydrodynamic dispersion relationship. The application of optimisation methods to identify parameter values from experimental data of time-varying vertical profiles of moisture content and solute concentration is investigated for a sandy soil. Multiple local optima are identified for both flow and solute transport relationships, but these alternative parameter sets are shown to be generally robust in prediction within the range of observed system states, which suggests some utility for this approach to parameter identification. Other possible forms of dispersion relationship are investigated, and several different formulations produce identical performance. This indicates that the dispersion relationship is ambiguous and hence the interpretation of analytical form from this type of experimental data may not be possible.