Heterogeneity of soil is usually captured by modeling hydraulicparameters as correlated random fields. These fields are mostly directlyor indirectly assumed to be multi-Gaussian. This implies that noinformation is used upon whether a certain parameter range is spatiallyconnected or forms isolated clusters. However, connectivity has beenfound to have a strong influence on parameters of upscaled flow models,in particular if the variance of parameters is high.
In this presentation, the influence of connected structures ofheterogeneous hydraulic parameter fields on upscaled flow and solutetransport models in the vadose zone will be discussed. Upscaled modelsare derived using homogenization theory. The models are analyzed fordifferent configurations of connected and isolated parameter ranges andfor different parameter contrasts. Homogenization theory is based on anexpansion of the flow- and transport equation in terms of the ratiobetween typical large length scale (for example the medium size) andtypical small length scale (for example the length scale of amacroscopic representative elementary volume). By analyzing differentparameter contrasts, quantified in terms of the expansion parameter, itcan be demonstrated that, for example, the occurrence of non-equilibriumeffects in the upscaled model depends crucially on the information aboutconnectivity of different parameter ranges. Besides the type of upscaledmodel, also the effective model parameters depend on this type ofinformation and can deviate significantly from effective parametersderived under the assumption that parameter fields are multi-Gaussian.