Environmental Tracers in Groundwaters and Porewaters to Understand Groundwater Movement Through an Argillaceous Aquitard

Abstract Inter-aquifer leakage through an aquitard can be an important component of groundwater flow and can occur by diffuse leakage or via preferential pathways along secondary permeability features. In order to properly characterize inter-aquifer leakage it is desirable to use both porewater from the aquitard in conjunction with a regional investigation of groundwater in the aquifers. The aim of this study was to characterize inter-aquifer leakage through a regionally extensive aquitard between the Great Artesian Basin (GAB) and the deeper Arckaringa Basin of Australia. Chloride concentrations in the aquitard porewater profile indicates that transport through the aquitard is dominated by diffusion, but there is evidence at t least one location for increased interaquifer leakage due to secondary permeability features.