Approximation of van Genuchten parameter ranges from hydraulic conductivity data.

The use of retention function and relative conductivity function is essential for the calculation of flow in a variably saturated media using the Richards equation. A widely used mathematical model for this is the Mualem-van Genuchten model which requires the shape parameters α and n. These, however, are difficult to obtain. When data is scarce, α and n are often taken from literature and may deviate largely from actual values. The current study presents a novel mathematical model for the approximation of α and n and for the further estimation of realistic value ranges, which may be used as parameter space e.g. for the calibration of a numerical model. The model was developed for cases where data is scarce and only values of saturated hydraulic conductivity are available. It is based on a large data set from literature and it is demonstrated that the model estimates mean values from that data set with a good accuracy. In order to show the applicability of the model, a second data set has been compiled anew (provided as electronic supplementary material). The model is incorporated into the current version of the freeware computer program HYPAGS, which enables easy usage. This article is protected by copyright. All rights reserved.