SIMULATION OF WATER-FLOW FROM A PERCOLATION TEST HOLE IN LAYERED SOIL

A finite-element program (TWODEPEP) was used to solve Richards' water-flow equation in cylindrical coordinates. Both saturated and unsaturated aspects of water flow from a percolation test hole were simulated. Inputs for the simulation model were the soil hydraulic conductivity, which was measured using the Guelph permeameter technique, and water-retention data for each layer of a silt loam soil. Pressure-head distribution and rate of water flow were simulated. A thin (approximately 10-mm) saturated zone near the water source, approximated by the region inside the zero-pressure line, was nearly constant in size with time, but the wetting front continued to advance. It was also found that the horizontal movement of water in the soil was dominant over the downward vertical movement. -from Authors