• evaporation;
  • falling head infiltration;
  • Philip

[1] Assumptions for many of the derived analytical infiltration models are either a constant infiltration rate or a constant head at the soil surface. For many realistic infiltration situations a falling head boundary condition is more appropriate. Philip showed that both the wetting profiles and the cumulated infiltration, in one-dimensional infiltration into homogenous soil with constant head at the upper boundary, can be written as a power series in tequation image. Presently, it is shown that a power series solution can be applied for falling head infiltration with evaporation. When comparing with the constant head solution, the falling head solution differs only from the second term, i.e., the sorptivity remains unchanged, a result which can be applied to falling head infiltrometer technique. The effect of a constant evaporation rate in the falling head scenario appears from the third term. In the presented numerical examples the retention model by van Genuchten and the hydraulic conductivity model by Mualem are applied. By comparing the wetting profiles obtained with a FEM solution it is shown that the discrepancies between the models are very small. Also, the estimation of the time at which the pond is emptied is concordant. The infiltration model is compared with a model by Parlange and colleagues, and a simple infiltrometer method for determining the saturated hydraulic conductivity is proposed.