SCALE PROBLEMS IN SURFACE FLUXES

Summary

ABSTRACT Partial analysis in the form of limiting analytical solutions is applied to the problem of infiltration into a semi-infinite column at constant initial moisture content. It is found as a result of such an analysis that: (a) the solutions for realistic assumptions concerning the soil moisture characteristics are bounded reasonably closely by an upper limit corresponding to constant diffusivity and ultimate infiltration rate equal to saturated conductivity and a lower limit corresponding to constant diffusivity and zero conductivity; (b) for both of the limiting cases of zero horizontal conductivity and infinite horizontal conductivity, the values of average sorptivity are insensitive to the form of the statistical distribution of spatial non-homogeneity; (c) the average sorptivity is less than the corresponding sorptivity based on the average scale parameter of a spatially variable soil and the average ultimate rate of infiltration is greater than the corresponding ultimate rate based on the average scale parameter.

INTRODUCTION

It is a privilege to contribute to this colloquium in honour of George Kovacs whom I valued as a colleague and a friend over a period of twenty years. In doing so I have sought to select a topic that would reflect his own special interests and his own approach to hydrologic problems. Thus, I have chosen to deal with conditions in the unsaturated zone because of his own interest in and contributions to subsurface hydrology.