Simulating Water Uptake by Tree Roots: An Initial Assessment

This paper explores issues related to the numerical simulation of moisture migration patterns associated with vegetation. Particular attention is given to prediction of soil suction variations in the unsaturated zone and in the vicinity of a single mature tree. A preliminary investigation is presented based on the use of Richard's Equation for unsaturated moisture flow incorporating a sink term. A numerical solution has been achieved via the finite element method for spatial discretisation along with a finite difference time-marching scheme. The model is first verified against a one-dimensional simulation for a uniform crop cover. An axisymmetric solution is then developed to represent water-uptake near an established tree. Field data and non-linear hydraulic properties have been sourced from independent published data. Numerical results have been validated by direct comparison to experimental/field data. The results obtained show a realistic moisture migration pattern can be achieved in this manner.