Approach for predicting the wetting front depth beneath a surface point source: theory and numerical aspect

Using experimental data, the continuity and the cumulative infiltration equations, a new expression for predicting the wetted soil depth was described. Knowing soil hydraulic conductivity K (h f ), initial and wetting front water content, this method enables us to calculate the maximum front depth Z f ( t ), beneath an emitter, by only measuring its radius R f ( t ) on the soil surface. To test this, we used the ADI finite difference method to solve Richards' equation for axisymmetrical water infiltration from a point source on the soil surface. To simulate the evolution of the wetted soil volume dimensions ( R f ( t ) and Z f ( t )), proper conditions were fixed for the wetting front boundaries. The Z f ( t ) predicted values were compared with those computed and measured during an axisymmetric water infiltration test on a silty soil for three different discharge rates. The results obtained showed good agreement between predicted, computed and measured data.