Science, Technology and Engineering

Environmental Geoscience

Postgraduate Projects

Quantifying groundwater discharge into rivers systems using radon-222 as a tracer

Jane McLeish

Supervisor: Dr John Webb

Radon-222 gas is a naturally occurring radionuclide that is produced from the radioactive decay of radium-226, one of the uranium-series isotopes. When radon-222 enriched groundwater enters and mixes with a surface water body (predominately of lower radon-222 concentrations due to gas exchange with the atmosphere, the radon concentrations in the water will increase. This allows for radon-222 to be used as a tracer for groundwater input into a stream.

Three river systems in central and western Victoria have been selected: Mt William Creek (just E of the Grampians), the upper Glenelg River (W of the Grampians) and the upper Loddon River (N of Ballarat). Previous studies by the salinity research group at La Trobe University indicate that these rivers experience substantial groundwater input at particular locations, e.g. along faults, identified in some cases by anomalies in the salinity of the stream water. These rivers have been selected because they are all important water sources for agriculture and local towns; in addition they span a variety of hydrological and hydrogeological settings.

Results obtained from this project will be used to identify, quantify and compare the groundwater input into the three rivers. This information will be very useful in the groundwater/surface water management strategies of these areas, by identifying particular areas of saline groundwater input that can then be targeted for treatment.