Simulation of soil moisture migration from a point source

Abstract

A computer model simulating moisture migration in soil from a drip source considering root water extraction (RWE) was developed. The model was formulated using Continuous System Modeling Program (CSMP).A two-dimensional non-linear unsaturated transient flow equation was solved using the principle of mass conservation and Darcy's law on soils of dwarf-apple orchards located in southwestern Quebec. A finite axisymmetric cylinder with homogeneous, isotropic and non-swelling soil was considered for the simulations. No flow conditions across the boundaries of the cylinder were fixed. The initial soil moisture contents in the soil profile observed in the field were input for the simulations.The macroscopic approach was used to compute RWE as a function of (THETA), Z and t. The RWE was assumed to be equal to evapotranspiration (EP) which was estimated using temperatures and the solar radiation index of the location.The moisture contents in the soil profile observed at the termination of emitter discharge were in close agreement with the simulated values. The soil moisture distribution was found to depend on the amount of water remaining in the soil and soil moisture retention characteristics. It is independent of the rate of emitter discharge, the depth of root zone and method of application