Explicit Infiltration Function for Furrows

Abstract

This study addresses infiltration from furrows or narrow channels. The basic approach is to develop the two-dimensional infiltration as a combination of the corresponding one-dimensional vertical and an edge effect. The idea is borrowed from previous applications for infiltration from disc and strip sources. The assumption is tested directly with numerical experiments using four representative soils and three furrow shapes (triangular, rectangular, and parabolic). The edge effect is the difference between the cumulative infiltration per unit of adjusted wetting perimeter and the corresponding one-dimensional infiltration. A general conclusion is that the edge effect is linearly related to time. In addition, it was observed that the two empirical parameters in the function used to relate the edge effect with time have narrow ranges and are related to soil hydraulic parameters, furrow shape, the boundary and initial conditions and additional geometric factors. The approach leads to a physically based infiltration function for irrigation furrows (or narrow channels) without the need to perform a fully two-dimensional simulation. Also, a simplified expression was found for the limiting steady-state case, which is analogous to Wooding’s equation for infiltration from a shallow pond.