SOIL WATER PROFILE DEVELOPMENT UNDER A PERIODIC BOUNDARY CONDITION

Abstract

A numerical solution technique was applied to the Richards equation for soil-water flow. Hysteresis in the water-content-pressure-head relation was incorporated into the solution procedure. Water content, pressure head, and flux time and depth distributions were calculated for a column of sand subjected to a periodic upper boundary condition. Two cases were examined: (1) an initially dry, deep (semiinfinite) sand column and (2) a sand column with a water table at a depth of 300 cm. In both cases the waveforms of water content, pressure head, and flux exhibited a progressive increase in phase lag and decrease of amplitude with depth. The highly nonlinear soil-water flow system introduced a high degree of harmonic distortion into the response of the system to a sinusoidal boundary condition.