Airborne Geophysics - the latest weapon in land management arsenal

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Airborne Geophysics is increasingly being used to support land management decisions, as it provides a unique view of the structures that influence the movement of salt and water through the landscape. The data it provides fleshes out information obtained on the ground to give a comprehensive view of a landscape.

How Airborne Geophysics Works

Airborne Geophysics (AG) has long been a standard tool in the mineral exploration industry, used to probe geological and ore body signatures within the earth’s surface. More recently, this has been turned towards the natural resource management (NRM) arena, with four distinct, but often complementary airborne technologies providing information on the properties of the earth.

(i) Airborne Electromagnetics (AEM) – entails the transmission of an electromagnetic pulse from an airborne platform which interacts with materials in the ground. Secondary currents are generated with the strength and longevity of these currents indicative of the conductivity of the materials the primary pulse has interacted with. This conductivity is a function of the amount of water, salt, clay and void space in the material and the depth from which the signal is penetrating. This can be calibrated through on-ground investigations, primarily sampling via bore holes of the materials and waters in the sub-surface at strategic locations.

The ability to accurately deduce the 3-dimensional sub-surface nature of these responses and the strong correlation to either salt stores of saline groundwaters, created a new industry in airborne ‘salinity’ mapping.

In addition to mapping groundwater flow systems, salt loads and the extent of clays, AEM can also be used to detect such things as buried pipelines and UXOs (Un-Exploded Ordinances)!

(ii) Radiometrics – reveal the geochemistry of surface cover and can be used to infer deeply weathered profiles (potential salt stores), or be useful in better defining soil maps or land management units. It can also be used to detect man-made radioactivity or contaminants. It cannot, however, directly measure salinity at the surface.

(iii) Magnetics – measures the variable magnetism across and beneath the landscape and is useful for probing underground geological structures such as faults, rock bars or buried ancient stream channels (paleochannels).  When combined with AEM, this can provide information on how groundwater moves beneath the landscape. It does not give good depth information, however.

(iv) Altimetry – is a useful by-product of the other techniques, as all rely on knowing precisely the position of the detecting equipment relative to the earth’s surface, so a Digital Elevation Model is readily generated. This allows detailed analysis of the catchment’s surface morphology.

Papers

• Interpreting Airborne Geophysics as an adjunct to Hydrogeological Investigations for Salinity Management: Honeysuckle Creek Catchment, Victoria (Part 1 of 2 - Main report). By Pauline English, Peter Richardson, Mark Glover, Hamish Cresswell & John Gallant
• Interpreting Airborne Geophysics as an adjunct to Hydrogeological Investigations for Salinity Management: Honeysuckle Creek Catchment, Victoria (Part 2 of 2 - Appendices). By Pauline English, Peter Richardson, Mark Glover, Hamish Cresswell & John Gallant

Project Reports

South Australia Salinity Mapping and Management Support Project [SA SMMSP]

Technical Reports published on this website:

• Salt Transport in the Bremer Hills, SA. Report for NAP South Australian Salt Mapping and Management. CLW Technical Report 50/02 November 2002. By Jim Cox, Kerryn McEwan, Phil Davies, Chris Smitt, Andy Herczeg and Glen Walker
• Salt Transport in the Bremer Hills, SA – FLOWTUBE modelling. Second Report for NAP South Australian Salt Mapping and Management. CLW Technical Report 06/03 Aril 2003. By Chris Smitt, JimCox, Kerryn McEwan,Phil Davies,Andy Herczeg and GlenWalker
• Salt Transport in the Bremer Hills, SA. Interpretation of Spatial Datasets for Salt Distribution Fourth report for NAP South Australian Salt Mapping and Management. CLW Technical Report 49/03 ?? 2003. By Chris Smitt, Jim Cox, and Phil Davies
• Dry saline land: an investigation using ground-based geophysics, soil survey and spatial methods near Jamestown, South Australia. CLW Technical Report 55/03 December 2003. By R.W. Fitzpatrick, M. Thomas, P.J. Davies and B.G. Williams
• Groundwater Recharge, Mixing and Salinity across the Angas-Bremer Plains, South Australia: Geochemical and Isotopic Constraints. CLW Technical Report 29/04 June 2004. By Richard G Cresswell & Andrew L Herczeg
• Groundwater Flow Systems and Salinity in the Valleys around Jamestown, South Australia Geochemical and Isotopic Constraints. CLW Technical Report 30/04 June 2004. By Richard G Cresswell & Andrew L Herczeg

Client Reports that will be published on DWLBC website [External site]:

• Application of Airborne Geophysical Techniques to Groundwater Resource Issues in the Angas-Bremer Plains, South Australia. Richard Cresswell and David Gibson. Report DWLBC 2004/ 35. September 2004. ISBN 0-9756945-2-9. ISBN 0-9756945-3-7
• Application of Airborne Geophysical Techniques to the Investigation of Salt Stores and Stream Salinity in the Bremer Hills, South Australia. Glen Walker, Jim Cox, John Wilford, Chris Smitt and Craig Liddicoat. Report DWLBC 2004/ 38. September 2004
• Application of Airborne Geophysical Techniques to Salinity Issues Around Jamestown, South Australia. Richard Cresswell and Craig Liddicoat. Report DWLBC 2004/ 37. September 2004. ISBN 0-9756945-4-5
• Application of Airborne Geophysical Techniques to Salinity Issues in the Riverland, South Australia. Tim Munday Glen Walker and Craig Liddicoat. Report DWLBC 2004/ 34. December 2004. ISBN 0-9756945-6-1
• Application of Airborne Geophysical Techniques to Groundwater Salinisation Issues in the Tintinara Region, South Australia. Glen Walker and Craig Liddicoat. Report DWLBC 2004/ 36. December 2004. ISBN 0-9756945-7-X
• South Australian Salinity Mapping and Management Support Project: Final Report. Glen Walker, Richard Cresswell, Tim Munday and Craig Liddicoat. Report DWLBC 2004/ 39. December 2004. ISBN 0-9756945-5-3

Links

• National Action Plan for Salinity and Water Quality

Staff

Fred Leaney, Glen Walker, Neil McKenzie and Hamish Cresswell