Abstract

Recent results from percolation theory as applied to the hydraulic conductivity of unsaturated porous media are compared with the frequently used phenomenological relationship due to van Genuchten. In applications so far percolation theory has proven to be predictive and unifying, while the van Genuchten phenomenology is intended only to be descriptive. To illustrate: the critical volume fraction for percolation is an analog to the residual moisture content, but a phenomenological result exists for the former in terms of the specific surface area, whereas the latter is intended only as a fit parameter. Second, it is recognized not to be possible to predict the hydraulic conductivity as a function of saturation using merely textural data—enough information about the pore space must be available to distinguish between various potential models. When the data are sufficient to confirm a fractal model, however, percolation theory yields a result that has several similarities to the van Genuchten parameterization. The analysis helps lead to a better understanding of the van Genuchten relationship.

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