A combined laboratory and field-based experimental approach to characterize the heterogeneity of granular aquifers

Effective groundwater resource management requires appropriate conceptualization of aquifer heterogeneity, which is challenging for pro-deltaic systems. This study focuses on heterogeneity within the Valin River paleodelta (Canada), a complex granular aquifer constituting a system that is a regional water supply source. This study integrates laboratory and field-based experimental measurements of various hydrogeological properties and classifies the sediments using diverse statistical techniques. It demonstrates the advantage of diversified characterization for a better understanding of aquifer heterogeneity. The hydrogeological properties-i.e., hydraulic conductivity (K) and porosity (n)-of 27 lithofacies identified in nine sandpits were estimated and assigned a range of values. The identified lithofacies were grouped into four operative-lithofacies before being assigned to three primary hydrofacies that were used to define the aquifer heterogeneity. The importance of integrated sediment and hydraulic properties assessment is that the techniques allow an understanding of the heterogeneity within a complex prodeltaic aquifer type. Two scales of heterogeneity are defined: (1) lithofacial scale wherein small differences in sediment texture (grain size properties), in sedimentary structures, and in other sediment features of lithofacies (mean grain diameter, sorting, skewness, and kurtosis) cause significant changes in K and n, (2) hydrofacial scale wherein specific lithology units define larger-scale aquifer flow and potential solute movement. The multi-methodology approach used for characterizing the aquifer heterogeneity is a prerequisite to complete necessary information for developing more accurate and complex hydrogeological models.