Connectivity of an alluvial aquifer: from theory to practice

摘要

The heterogeneity of the alluvial aquifer controls both water flow and contaminant transport. In particular, the presence of organised features such as permeable connected levels (connectivity) has a significant effect on water flow rates and travel times, because it can lead to channelling. The task of defining a rigorous quantitative measure of connectivity for continuous variables has failed so far, and thus there exist a suite of connectivity indicators which are dependent on the specific hydrodynamic processes and the interpretation method. Nevertheless, limited effort has been devoted to apply the connectivity concept in real case. In the present paper, the effects of connectivity on flow and transport are studied for a large-scale real aquifer: the alluvial plain of Milan (Northern Italy). Based on geological and hydrogeological field data, numerical modelling of flow and non-reactive transport was carried out and results were used for testing several types of connectivity indicators. Also scale dependency of connectivity was analysed, pointing out empirical laws describing connectivity as a function of observational scale. Finally, upscaling method based on connectivity was applied to verify its effectiveness in a large-scale real aquifer.