Groundwater–Surface Water Interaction: Process Understanding, Conceptualization and Modelling (Proceedings of Symposium HS1002 at IUGG2007, Perugia, July 2007). IAHS Publ. 321, 2008, 134-138.

Discharge of saline groundwater into a freshwater stream – River Murray, Australia

Gudrun Massmann¹, Andrew Love², Craig Simmons², Julianne James-Smith³ & Andrew Herzceg⁴

1 Freie Universität Berlin, Institute of Geological Sciences, Hydrogeology Group, Malteserstr. 74-100, D-12249 Berlin, Germany

massmann@zedat.fu-berlin.de

2 Flinders University, School of Chemistry, Physics and Earth Sciences, GPO Box 2100, Adelaide, South Australia

3 South Australian Government, Department of Water, Land and Biodiversity Conservation, GPO Box 2834, Adelaide, South Australia

4 CSIRO Land and Water, Private Bag no. 2, Glen Osmond SA 5064, Adelaide, South Australia

Abstract Salinization of water resources is a major problem on a global scale. In the Loxton-Bookpurnong irrigation area (South Australia) saline groundwater is pushed towards the river by advective flow. Groundwater was sampled from beneath the river. In all cases, fresh river water overlies saline groundwater, a stable stratification with regard to the fluid density. The salinities encountered partly exceed those of seawater. Modelling was done to determine what role variable-density flow behaviour plays in surface water–groundwater interaction in a stably-stratified fresh surface water–saline groundwater interface. Comparison of measured and simulated concentrations vs depth profiles reveals a qualitative resemblance of the profiles for simulations where density was the dominating force. The clear stratification of fresh over saline water, with a sharp increase at a certain depth, leads to the hypothesis that the high density of the fluid may partly suppress discharge in stagnant pockets below the river.

Key words salinization; discharge; surface water/ groundwater interaction; density driven flow; riverbed aquifer