Helicopter survey maps groundwater in the Condamine Alluvium
Keen sky-watchers in the Dalby and Cecil Plains region will be able to spot a low-flying helicopter with a large rectangular frame suspended underneath it flying in formation from the 8th of May for up to 10 days.
The sight, while unusual, is no cause for alarm. The helicopter is conducting an airborne electromagnetic survey (AEM) gathering data that will help the Office of Groundwater Impact Assessment (OGIA) further understand the groundwater resources of the Condamine Alluvium.
OGIA is an independent office responsible for the cumulative assessment of groundwater impacts in areas of intensive coal seam gas and coal mining development.
OGIA Director Groundwater Conceptualisation Steve Flook said the survey was an important part of a research project to provide information on the shallow geology and groundwater system, in order to better understand potential impacts of resource extraction in the region.
“The survey will also help us improve our knowledge about the potential groundwater connectivity of the Horrane Fault, which is a subsurface geological structure, with the Condamine Alluvium,” Mr Flook said.
During the survey, a transmitter will emit a very weak electromagnetic (EM) signal from the frame hanging from the helicopter and then measure the return signal once it has interacted with shallow geological material and groundwater.
“Since 2012, OGIA has significantly advanced the understanding of the groundwater connectivity in the Condamine Alluvium with progressive improvements made over time.
“As part of this process, the Horrane Fault – a geological feature that offsets the coal seams and the deeper formation underneath the Condamine Alluvium – has so far been mapped using seismic and other data.
“While seismic survey has provided a good understanding of the extent of the fault in deeper formations, it has not been effective in shallower parts of the Condamine Alluvium. This is where an AEM survey can support further understanding,” Mr Flook said.
AEM surveys are used to provide information on groundwater systems including the geology and the presence of structures and geological boundaries – typically at shallow depths of less than 200 metres. This is achieved through the measurement of natural variations in the electrical properties of soil, rocks and water. AEM surveys are carried out all over the world and are considered very safe.
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Last updated: 04 May 2023