18.104.22.168. Brackish Na–Cl–HCO3 water types
Using a combination of multivariate statistics, assessment of major ion relationships and geochemical modelling the hydrochemical Carminomycin in a large alluvial aquifer, the upper Condamine alluvium in eastern Australia was assessed. The alluvial aquifer is a critical groundwater resource for irrigated agriculture in the area, and it overlies a commercially-viable, shallow coal seam gas (CSG) reserve: as a result recharge processes and alluvium–bedrock connectivity were a focus of this study, particularly the evolution of Na–HCO3 and Na–HCO3–Cl water types and their occurrence in the alluvium.
In general, no relationships were observed between CSG groundwater in the WCM and the alluvial groundwater. Hydrochemical similarities between a shallow alluvial groundwater sample and CSG groundwater identified during the hierarchical cluster analysis (HCA) were shown to be clustering artefacts caused by the evolution of similar water types via different processes. This highlights the risk associated with the sole application cluster techniques to identify potential aquifer connectivity in CSG-related studies.