Description of soil water characteristics using cubic spline interpolation

Solutions of differential equations describing soil water behavior frequently require a mathematical function for the soil water characteristics, Although spline interpolation provides a method to connect the data points, in many cases its use yields poor results. The mathematical representation of the soil water characteristic may also be shaped according to the imagination and judgment of the investigator. In such cases, some additional virtual data points are chosen through which the spline function passes exactly to yield a mathematical description of the entire curve consistent with the initially measured points. A computer program SWC-SPLINE written in Delphi 2 allows the investigator to easily mark and change the position of the assumed virtual data points interactively according to visual inspection.