In a vertical or rather a 3D model a numerical modelling of a partly unsaturated groundwater aquifer can be carried out. This is carried out in SITRA at basis of the pressure-saturation functions and the function of the relative K-value for van Genuchten .
In SITRA three sets of parameters for the parameters residual saturation (Sres), inverse of the water inflow pressure (a), pore size index (n) and specific parameters of the relative K-value function (l) are predefined. Depending on K-values defined the in the model file they are automatically assigned to the appropriate soil types and van Genuchten parameters.
The exact allocation of the K-values and the soil types is given in a table in the chapter: “Data structure of a groundwater model, saturation”.
Calculation with van Genuchten-functions