The Great Artesian Basin (GAB) is an aquifer system that extends across Australia covering over 22% of the continent and is a vital support system for ecosystems in the region. As part of the Australian National Water Commission's (NWC) GAB Project, research is being conducted to understand the aquifer including studying the discharge of springs and determining flow paths of the aquifer. Water sampling at springs that are a part of the Freeling Spring Group were used along with Electrical Resistivity Imaging (ERI) data to evaluate evidence of mixing between the GAB aquifer and waters from the adjacent basement aquifer in the Peake and Dennison Ranges (PD). Nine springs were used to evaluate fluid chemistry of the Freeling Spring Group. ERI data were collected along three orientations over the Freeling Spring site. The ERI data, which extend for 550 meters laterally and 110 meters vertically, indicate three possible flow lines providing mixing at the spring orifice similar to what would be predicted from traditional conceptual models. Regional water samples of springs were used as end members to evaluate chemical mixing models for waters at the site. The chemistry of spring water samples indicates that the water emanating from the Freeling Spring Group is a mixture of waters from both the GAB and the PD, which confirms the ERI evidence for mixing at the site. The data suggest the mixing occurs along a structural feature in the Peake and Dennison Ranges and that the spring water maintains a strong PD signature even well east of the fault zone.Boone Pickens School of Geolog
