Abstract
The architecture of sedimentary bodies determines the heterogeneity of many aquifers. Thus, for environmental risk-assessment and quantification of clean-up efficiencies, determination of the spatial distribution of hydraulic properties is required. In this study, outcrop analogues of glaciofluvial gravel-bed deposits are used for a process-based analysis of sedimentary heterogeneities, which in turn are transformed into hydraulic parameters. Three scales of heterogeneities are distinguished: (a) the lithofacies-scale is formed by unique transport and depositional processes that form the fundamental building blocks (hydrofacies types), (b) the depositional element-scale shows distinct geometrical characteristics (internal structure and bounding surfaces) and determines the local distribution of lithofacies and, hence, the correlation structure of permeabilities, (c) the architectural-scale of gravel bodies is formed by the stacking of depositional elements, which is controlled by the dynamics of aggrading paleofluvial systems. Comparison of numerous gravel pits in SW-Germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types. The facies analysis results in three conceptual facies models of proglacial river systems, which are regionally classified as ‘main-’, ‘intermediate-’ and ‘minor’ discharge types. Based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the GIS system Arc Info. The two-dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow. Modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics.
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