Alternative Model for Predicting Soil Hydraulic Conductivity Over the Complete Moisture Range

Abstract

Considering film flow in the development of a soil hydraulic model has become a key method for improving model performance under dry conditions. With the considerable improvement in model performance, the trade-off is often to increase the model complexity, thus limiting a model's application. In this paper, an alternative model is presented to predict soil hydraulic conductivities over the entire moisture range. In contrast to existing models that treat conductivity as a summation of the capillary and film components, the proposed model applies a single equation to capture the variation of the two conductivity components. The new model, therefore, presents a simple form, with no extra parameters added to the basic capillary models. Model testing with 24 soil data sets revealed that it was successful in predicting conductivities over the complete moisture range. A comparison with existing models demonstrated that the proposed model was generally in higher agreement with observations, achieving a much lower mean value of the root mean square errors for the predicted conductivities.