Studies on the infiltration-discharge of rain water and translation phenomena in soil

Abstract

Infiltration and discharge of rain water and water movement in soil were investigated by a numerical analysis based on a one-dimensional infiltration model. A simple approximate formula for the piezometric head and water content distribution in soil in a steady state was obtained. Computational results in unsteady state indicated that the vertical downward speed of the wetting front is generally much larger than that of a tracer, which is assumed to be injected together with the rain water at the soil surface. Theoretical considerations were then developed to relate the movement of the wetting front and that of the tracer front to water movement in soil. Finally, numerical analyses were performed for various precipitation intensities, under various initial soil moisture conditions and with various soil properties. The speed of the wetting front approaches that of the tracer as the precipitation intensity increases, as the initial soil moisture decreases, and the grain size increases.