Relating lithofacies to hydrofacies: outcrop-based hydrogeological characterisation of Quaternary gravel deposits

A considerable part of today's drinking water supplies in Europe and North America rely on clean groundwater from gravelly Valley aquifers of Quatemary age. The sedimentary architecture, the distribution of lithofacies and of architectural elements in such heterogeneous deposits are of fundamental importance for the analysis of groundwater flow and contaminant transport. As the aquifers are not directly accessible for observation, representative outcrop analogues were used to study the sedimentology on a local scale. Conventional sedimentological classification schemes were adapted for the purpose of hydrogeological evaluations. Measurements of hydraulic properties were then used to define a set of 5 hydrofacies from 23 possible sediment lithofacies. A digital-photographic mapping procedure was developed to allow fast data acquisition in the field. The sedimentologically interpreted outcrops were stored in a GIS style database and thus allow the output for further sedimentological or hydrogeological analysis. (C) 1999 Elsevier Science B.V. All rights reserved.