Effects of medium characteristics on finger flow during soil water redistribution

Research on finger flow has practical guiding significance to effective utilization of agricultural water and fertilizer resources and to protection of environment and water against pollution. In order to understand the effects of medium characteristics on finger flow during the redistribution following the infiltration process of soil water, in this paper, an experimental study was carried out to discuss the effects of the characteristics of soil medium on the development of finger flow during redistribution with two different grain sized sands. The medium characteristics considered in this work were soil texture, soil structure and soil initial water content. Three soil structures, i.e. homogeneous soil, texture-layered soil and humidity-layered soil, were designed in this study. The experimental results showed that finger flow could easily occur in dryer and coarser homogeneous soil during water redistribution since both wetter and finer soil medium were proved to have disadvantageous effect on development of finger flow. The moving speed of wetting front was determined by both development status of finger flow and soil initial moisture content. Moreover, finger flow was greatly advanced in texture-layered soil with coarser soil overlaid by a finer soil layer compared with that in homogeneous dry coarser soil during water redistribution though it needed more time to develop, while the development of finger flow was restrained in humidity-layered soil with a wetter soil layer overlaid by a dryer soil layer. It was suggested that soil characteristics such as texture, structure and initial water content would have important effects on formation and propagation of finger flow during water redistribution.