Bundaberg Groundwater Investigation, Australia – A Case For The Benefits Of Extensive Use Of Geophysics In Groundwater Investigations

In 1998/99 the Department of Natural Resources (DNR) in Bundaberg, Queensland,<br>Australia contracted Geo-Eng Australia (now GHD Pty Ltd), to undertake a major joint study of the<br>coastal groundwater system of the Bundaberg Irrigation Area (BIA) which was experiencing<br>problems with the unregulated use of much of the aquifer and seawater intrusion problems. The<br>Bundaberg Groundwater Project is arguably the largest integrated geophysical, drilling and<br>hydrogeological project for water resources assessment undertaken in Australia.<br>The Project was a pre-cursor for a proposed new BIA groundwater model. One primary<br>project objective was to acquire sufficient data on the extent and properties of the groundwater<br>system to redefine the conceptual hydrogeological model. Another primary objective was to<br>systematically apply integrated geophysical, geological and hydrogeological techniques and gather<br>permeability data, directly and empirically, for identification of permeability trends.<br>The project provides a case study, showing the value of a strong commitment to the largescale<br>use of routine and innovative geophysics throughout a major groundwater investigation.<br>Firstly, the project budget allowed use of ground resistivity (of 702 kms of traversing and<br>273 soundings), seismic reflection soundings and multi-parameter geophysical logging (270<br>new/existing holes) on a scale generally not contemplated in groundwater studies. The extensive<br>geophysics guided a major drilling program of 130 new holes including 106 new piezometers<br>optimised in position and depth.<br>Secondly, it showed the value for groundwater management decision-making of an integrated<br>analysis of disparate datasets (airborne and ground geophysics, hydrogeological, topographic,<br>hydrochemistry and geophysical logs).<br>Thirdly the application of sequence stratigraphic analysis techniques, to geophysical log data<br>defined a new conceptual hydrogeological model and understanding of the hydrogeological context<br>and information value of each existing and new piezometer.<br>Finally, the geophysical logs assisted by the surface geophysics, proved useful in providing<br>an assessment of permeability trends for groundwater model building.