Author(s): F. Stauffer; M. Rauber

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Abstract: Statistical information on sedimentary structures which was determined from natural gravel deposits in north-eastern Switzerland is used to characterize aquifers with respect to their transport phenomena. These aquifers consist of a background gravel matrix with embedded lenses consisting of different material. One of these lens types represents highly conductive open framework gravel, which results in a bimodal probability density function of the hydraulic conductivity of the overall gravel material. Based on this information two approaches to modeling macrodispersion are presented. In the first one distinct unconditioned realizations of synthetic block shaped facies type aquifers are generated numerically such that they have the same statistical properties with respect to facies geometry and hydraulic properties as the deposits themselves. Numerical experiments simulating saturated flow and transport are subsequently performed with the help of a three-dimensional finite element flow model and a corresponding random walk transport model. A total of 100 experiments allowed estimates of apparent distance dependent macrodispersivity values. In the second approach, statistical parameters were directly applied to an analytical stochastic modeling of apparent macrodispersivity using a unimodal and a bimodal approach. Differences present in the model results can mainly be attributed to uncertainty in the input parameters.

DOI:

Year: 1997