Modelling infiltration: A measurable parameter approach

Development of a 2-stage, measured parameter, infiltration model is reviewed. The model has been verified against finite difference solutions of the unsaturated flow equation, by laboratory tests and has been evaluated under field conditions. Progress of recent research utilizing this model is discussed. Results of recent research indicate that the effects of air entrapment on hydraulic conductivity must be taken into account. A reasonable approach to this problem is to evaluate relative conductivity as a function of relative moisture content and use this relationship to evaluate hydraulic conductivity at field saturation. Additional factors which have been investigated include air viscous effects and the effects of tillage and surface sealing. While significant progress has been made toward including these effects in the model, additional research is required. An attractive attribute of the model is that all parameters utilized in the model are measurable and thus no parameter fitting is required. The paper discusses how parameters may be evaluated and how the model operates, and presents some examples of model predictions under different conditions of soil composition and rainfall pattern.