Investigating the spatio-temporal variability in groundwater and surface water interactions: a multi-technique approach

This research investigates the complex interactions between groundwater and surface water in the Tambo and Nicholson rivers, located in southeast Australia. By employing a combination of scientific techniques, including measurements of radon-222 (222Rn), chloride (Cl) concentrations, flow gauging, head gradients, electrical conductivity (EC), and temperature profiles, the study aims to understand how water moves between these two systems. The findings indicate that the amount of groundwater flowing into the Tambo River is influenced by the local topography. Areas with greater variations in elevation show higher groundwater discharge. While methods like chloride mass balance provided lower estimates for groundwater discharge, radon mass balance and differential flow gauging yielded higher results, suggesting complexities such as bank return waters affect the accuracy of different methods. The research also highlights that both rivers are significantly connected to the groundwater system, which responds dynamically to rainfall events. Groundwater contributes a larger proportion to river flow during periods of low flow (baseflow) and a smaller proportion following rainfall.