A multidisciplinary research on aquifer analogues to assess the effect of hydrofacies heterogeneities at fine scale on solute transport al large scale

A multidisciplinary approach (sedimentology, hydrology, geophysics, applied mathematics and informatics) is necessary to study "field virtual aquifers" or "aquifer analogues", i.e., geological bodies which are well exposed, can be analyzed with field surveys, and can be assumed to be similar to the buried aquifers from the geometrical and lithological point of view. They are used to build "numerical virtual aquifers", i.e., 3D arrays of categorical or continuous variables, which describe the spatial distribution of physical properties, share the same statistical properties as the field data and can be the basis to perform synthetic experiments with numerical flow and transport models. Therefore, virtual aquifers are a tool to understand the effects that fine scale hydrofacies heterogeneity has on solute transport at large scale. This is done through the following steps. a. Collection of geological, geophysical and hydrological field data. b. Hydrostratigraphic description of the aquifer analogues. c. Laboratory analysis on samples to determine grain-size-distribution and hydraulic conductivity of different facies. d. Geostatistical simulation of the hydrofacies distribution. e. Set up of virtual aquifers. f. Flow modelling and determination of the equivalent conductivity tensor. g. Numerical experiments of 3D convective transport of a non-reactive solute for an average 1D flow and determination of the lagrangian dispersion tensor and of the effective eulerian dispersion coefficients. h. Numerical experiments of 1D large-scale convective transport with stochastic transport models based on the Kolmogorov-Dmitriev theory in a Montecarlo framework. This approach has been tested on aquifer analogues representative of the hydrostratigraphic features of the alluvial Po plain (Northern Italy).