Geophysics

In the Angas Bremer region of the Murray Basin , the principal goal of the geophysical survey was to map groundwater systems rather than salinity. A combination of airborne geophysical techniques and rigorous field and chemical analyses has shed light on the recharge mechanisms and groundwater movement across the Plains and helped define the extents of the groundwater systems and the origins of salt in the region.

The prime objective of the project in the Angas Bremer Plains was to provide information that allowed prevention of, or better management of shallow, saline groundwaters and soil salinity, and protection of sensitive aquatic habitats.

For sustainable management into the future, local irrigators need to know:

• At what rate can they support future expansion of irrigation?
• How robust is the system?
• How do they control the water balance and the salt balance?
• Where are the best sites to re-vegetate for recharge control and for other environmental benefits?

With the amount of information now available for the Angas-Bremer Plains region, we now have the potential to develop truly sustainable conjunctive water management decisions from the paddock through to catchment scale. That is, we can use all water resources, whether surface or groundwater, naturally or artificially recharged, in a sound, responsible, sustainable manner. This could be driven, not by hypothetical ideals and models, but through pro-active response to real data: using data as a sound basis for policy.

This report is one of a series of final site reports summarising results for the South Australian Salinity Mapping and Management Support Project (SA SMMSP). Conducted under the auspices of the National Action Plan for Salinity and Water Quality (NAP), the project had three underlying goals:

• to test airborne geophysical techniques (in particular electromagnetics [EM], radiometrics, and magnetics) to determine their value for salinity management,
• to further refine and adapt the technology to suit this application, and
• to provide specific information to assist with salinity management in five key areas of South Australia .

The SA SMMSP adopted a pioneering approach compared to traditional research programs involving the acquisition of geophysical data. Instead of accepting data collected in an arbitrary manner, which may add to knowledge but be of little use for management, considerable thought went into how the data generated could contribute to the implementation of salinity management options applicable at each site. By providing interpreted, appropriately targeted, spatial geophysical data and associated decision support tools, the program seeks to reduce the impacts of salinity on land, surface water quality, groundwater quality and biodiversity.

(Richard Cresswell,[CRC LEME/ CSIRO Land and Water], Application of Airborne Geophysical Techniques to Groundwater Resource Issues in the Angas-Bremer Plains, South Australia, 2004)