A Critical Assessment of Two Phase Flow

Difficulties associated with the direct measurement of unsaturated hydraulic conductivity have prompted the development of empirical models that predict unsaturated conductivity using transformations of the more easily measured moisture retention and saturated hydraulic conductivity data. This thesis evaluates the predictive ability of three such models: the Brooks Corey model, the Campbell model, and the van Genuchten model. Seven soil types totaling 71 soil samples are analyzed. Predictive models use measured saturated hydraulic conductivity and parameters generated from the moisture retention curve to predict the unsaturated hydraulic conductivity. A nonlinear least-squares optimization procedure is applied to the moisture retention data to generate the best fit parameters. Results from the analysis indicate that these models do not. accurately predict the unsaturated conductivity. The models do not characterize the natural variability found in aquifers. A correlation is observed between the er-ror in prediction and the mean grain size; deviations between the measured and predicted conductivity increase as the texture of the material becomes coarser