Laboratory Simulation of Preferential Flow of Water through Soil-Tongues.

Preferential flow is a phenomenon, which is considered as one of the main mechanisms transporting the contaminants rapidly from the vadose zone to groundwater, while depleting the nutrients in the attractor zones in agricultural lands. Simulations using VS2DI software developed by USGS has indicated that soil-tongues formed at the boundaries between soil horizons can greatly enhance the preferential flow by carrying soil water in to deeper areas of the horizon lying below. Therefore, studying the behaviour of soil water movement through soil-tongues would assist the soil water and nutrient conservation as well as prevention of contamination of groundwater.

A physical model containing two horizons comprising of fine and coarse sand and two soil-tongues at the boundary between the two soil layers was constructed in a plexiglass container. Water was applied using point sources arranged in a grid at the top and changes in water content inside and outside the soil-tongues over time were monitored using TDR probes and analysed.