Appropriate Methods for Internodal Conductivities in Unsaturated Soils

Abstract

This study used the numerical method to determine the infiltration rates for sandy and clayey soils, being soils commonly found in Ado - Ekiti, Ekiti State of Nigeria. The numerical method involves the development of a finite difference model for vertical flow of water in unsaturated soils. The finite difference model was developed by finding the finite difference forms of the Darcy and Continuity equations separately and solving in sequence. The internodal hydraulic conductivity in the Darcy equation was computed using the geometric and harmonic averaging methods. Stability of the model was assured by setting criteria for the choice of depth and time increments. The model was validated with published parameters of Vauclin et al., (1979) and Philips (1957). The geometric mean method is suitable for fine soil and simulation for short time infiltration in coarse soil, whereas the harmonic mean method is only suitable for long time in fine and coarse soils.