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Morphological characterization of the spatial variability of hydrostratigraphic units

Abstract:

In order to study groundwater flow and contaminant transport it is very important to model the aquifer heterogeneity in terms of the spatial distribution of its hydrostatigraphic units. These units can vary strongly in thickness and can also be geometrically anisotropic and present different features concerning its neighbourhood relationships. To take into account these spatial features, variograms and cross-variograms of the respective coding indicator variables are calculated. The information extracted from these variograms and cross-variograms can then be used to characterise the mutual arrangements between the different stratigraphic units, namely the neighbourhood relationships. Whatever the model used (mosaic model, diffusion-type model or model with indicator residuals) a comparison of simulation results is needed in which, particular emphasis is given to the characterisation of the contiguity between the stratigraphic units. Here the use of mathematical morphology tools can help to identify important features like the presence of isolated units, for instance, and also to characterise the results of the estimation or simulation procedures in respect to the shape and granulometry and to establish the graph of neighbourhood relationship. The aquifer under study is the unconfined unit of Tejo groundwater system and the area covered is located in Setubal Peninsula where 2 waste disposal sites exist.