EXAMINATIONS ON THE STABILITY AND ACCURACY OF A CONTINUITY-SPLITTING SUBSURFACE FLOW MODEL

Abstract

In this study, the accuracy and stability of a subsurface flow model previously reported by the authors was examined. The model is based on splitting the flow continuity equation into vertical and horizontal components. Vertical flow is computed by Richard's equation in the unsaturated zone, and lateral flow is computed by Darcy's law, assuming that most of the lateral flow occurs in the saturated zone. In joining these two parts of the continuity equation, a systematic error occurs, but this can be reduced by introducing a correction factor to the height of the vertical flow results. Use of this factor also improves the stability of the model, which is stable for most natural groundwater conditions.