Salinity is a natural aspect of the Mallee landscape, and managing it effectively requires accurate data to safeguard both the environment and our vital irrigation industries.
Recognizing this need, the Mallee Catchment Management Authority (CMA) is embarking on a crucial data update. This marks the third survey of the Murray River corridor using the current methodology, the first since 2007.
Helicopter airborne electromagnetic (AEM) systems carry transmitter and receiver coils mounted in a frame slung beneath the helicopter. An electrical current is pulsed through the transmitter coil which produces
a primary magnetic field. This field induces eddy currents in the ground, which then create their own secondary magnetic fields. The strength of the secondary field fluctuates with varying ground conductivity which may be influenced by changes in soil salinity or changes in the quality of groundwater.
The decay of the secondary field is measured by the receiver coil located beneath the helicopter and the response can be used to tell us about ground conductivity as it varies with depth. These fields last only a few milliseconds.
More detailed information is available online at Airborne electromagnetics Geoscience Australia or SkyTEM Surveys – Airborne Electromagnetic Surveys Worldwide
Geoscience Australia also has a great video showing how the technology works, which you can watch here:
How Airborne Electromagnetic (AEM) Surveys Work – Helicopter
There is no health risk from the AEM system while in operation. Electromagnetic (EM) fields from the AEM system are tiny compared to EM fields generated by household wiring or radio, mobile phone and TV antennas; and the currents generated in the ground are of the order of micro to nanoAmps.
The aircraft altitude and speed also limits exposure.
For more detailed information, visit Australian Radiation Protection and Nuclear Safety Agency
AEM surveys cause no harmful effects to horses and other livestock, but the low flying helicopter may cause some annoyance to some animals for a short period of time.
Horse/livestock owners are encouraged to consider how best to care for their animals while the AEM survey is flown in their immediate area. It may be helpful to consider:
Airborne Electromagnetic Surveying, or AEM, is an accurate and cost-effective way to collect the necessary data to inform ways to better manage salinity.
Salinity is a naturally occurring part of the Mallee landscape, but we need the best data possible to manage it for the future of sustainable irrigation development.
AEM surveys are undertaken by a low- flying helicopter with a transmitter and receiver coil below it. The signals received through this non-invasive testing technique provide data that can be used to model groundwater to around 40m below the surface.
AEM is used around the world. AEM technologies have been used over various regions across northern Australia including the Ord irrigation district, southwestern Australia and previously in the Mallee in 2005 and 2007.
The survey will be undertaken from March- June 2024 to map saline groundwater in the Murray River corridor. This is the third time the region has been surveyed using this method (previously 2005 and 2007). It is being resurveyed in 2024 using improved technology to understand how the landscape is changing over time. Local horticulture has also expanded significantly since the last survey was conducted.
AEM surveys need to be flown when there is unlikely to be extended periods
of rain or strong wind, which means autumn is a good time to undertake the survey in the Mallee. The COVID pandemic slowed down the process of project commencement and the 2022 flood event postponed scheduled survey works by 12 months as large areas were inundated. The project is currently in delivery with survey capture to begin in March 2024.
There will be no direct impact on your property while the survey is undertaken.
Anyone working on your property is likely to see the helicopter as it undertakes the low-level surveying. Translated materials explaining the survey are available through the Mallee CMA.
The helicopter will fly at around 80 to 120km per hour at about 50 metres above the ground. The truss structure under the helicopter collects the data – it looks like a large, upside-down Hills Hoist clothesline; it is non-metallic and very light.
Surveys will not be flown directly over built-up areas, although the helicopter may pass nearby at times.
The sound of the helicopter is a similar noise level to a tractor motor, lawn mower or leaf blower.
There is no health risk from the AEM system while in operation. Electromagnetic (EM) fields from the AEM system are tiny compared to EM fields generated by household wiring or radio, mobile phone and TV antennas. The aircraft altitude and speed also limits exposure.
The AEM survey will provide a regional data set that provides:
For the first time, the survey will include information on how salinity is impacting the floodplain as well as the Murray River channel.
This is due to changes to the Water Act that now require the monitoring of salinity impacts in the landscape as well as in the river.
The information collected by the AEM survey will be ground-truthed through sampling of the region’s bore monitoring bore network.
Simultaneously, this work is being complemented by in-river sampling to assess the connection between saline groundwater and the river.
The final data will show salinity and groundwater trends over time at a regional scale, which will help support the protection of the environment and our region’s $1.29B1 horticultural industry over the next 20 years, enabling the targeting of efficient capital works to reduce, prevent and offset the impacts of salinity on landscapes and the Murray River.
The survey will not:
The AEM survey and the development of final products is being funded from salinity impact charges paid by irrigators. The charges are generated when a new water- use licence (WUL) is created or an existing water-use licence is varied to allow an increase in megalitres of annual use limit (AUL). The purpose of the charge is for
the WUL holder to contribute towards the cost of works or measures to mitigate or offset the salinity impact of irrigation. The responsibility for managing and mitigating IIS has been delegated to the Mallee CMA by Ministerial Instruments.
AEM is the least invasive and the most time and cost-efficient way to gather the information required.