Groundwater Survey Project

Salinity Insights For Irrigators and the Mallee Community

A groundwater survey using Airborne Electromagnetic technology –– is a method used to collect information about groundwater salinity and the underlying hydrogeological conditions of the land. 

The AEM surveying system consists of a transmitter and receiver coil suspended from a low-flying helicopter. The helicopter
completes a series of surveys in parallel lines approximately 200 metres apart, across the total survey area (22,000km).

The transmitter coil emits a current, similar to a mobile phone, which generates a magnetic field in the surrounding ground and air. Across the area being surveyed, the current is turned on and abruptly off, with a secondary magnetic current introduced and received by the receiver coil. 

This process enables the collection of groundwater modelling data that can inform groundwater salinity levels in our region. 

The Mallee and its unique climate is the perfect place for cropping and  horticulture.

Over time, irrigation practices and weather events have impacted groundwater profiles and the salinity levels found in our soil. 

The groundwater survey using AEM technology provides information to monitor and mitigate the impact of salinity in our region. Data collected informs groundwater modelling, salinity accounting, and the underlying hydrogeological conditions that help design and prioritise projects, future development and delivery of environmental water and other projects.  

Since the 90’s, the impact of salinity has been monitored by the Mallee CMA, however the most current AEM data available is from the previous groundwater monitoring surveys undertaken in 2005 and 2007. 

Results from these surveys were used to inform groundwater modelling, salinity accounting, upgrades to the Mildura Merbein Salt Interception Scheme and the prioritisation of projects and remedial works in areas identified at risk from salinity. 

An example of the benefits of the groundwater survey data collected from 2005 is that it informed the operation of the Merbein salt interception scheme to the extent that the scheme now operates with less than half the number of bores originally used – same benefit but half the cost.

The data collected during the project is analysed and collated by the survey team, and where applicable compared to past surveys to analyse how irrigation and agricultural practises are impacting salinity levels. 

The data can be used to inform irrigation and land development practices, and to assist in implementing best practice models across a variety of sectors. 

Gaining a better understanding of the salinity impacts on the soil; can assist in informing areas at risk from salinity, aid in informing growers and landowners in their decision making and help prioritise projects to mitigate and manage the impacts of increased salinity. 

With the last groundwater AEM survey taking place in 2007, it was time to update the information to provide insight into the current levels of salinity in groundwater which has a ripple effect into the levels within our wetlands, floodplains, and river systems.

The electromagnetic current emitted by the groundwater survey system is similar to the current emitted by a mobile phone connecting to a phone tower. 

There is no impact to health or wellbeing from the survey, with research indicating the wiring in a domestic household exposes people to more electromagnetic energy than the AEM system. 

Project Managers will work with farmers and livestock  owners within the flight path to ensure animal wellbeing is managed, as livestock such as horses and alpacas may react to the noise from the low flying helicopter. 

The Mallee CMA will be undertaking extensive communications and engagement leading up to and during the groundwater survey. Communications will include using social media, Mallee CMA website, radio, newspaper and other channels. The community will have an opportunity to provide feedback and where possible residents within the flight path then flight days or paths may be changed to accommodate specific needs.

The groundwater AEM survey process can be impacted by weather conditions and other environmental factors unique to the climate and geography of the region. A determination of the exact timing of the AEM flights will be made after a review of the flight window is undertaken with the chosen contracted organisation.

The groundwater survey (helicopter) will be undertaken in 2024, however important work in the field will also be carried out during 2023.

Mallee CMA, with support from the Victorian State Government, are overseeing the survey process as part of our regulatory obligation to implement processes to mitigate or offset salinity impacts of irrigation. 

A specialised team has been established to resource the project and support the flight team, to ensure community members are given adequate information prior to the survey period commencing and to be on hand to answer any queries throughout the survey. 

Across the Groundwater survey period, Mallee CMA will provide consistent updates on the status of the project which can be found on the Mallee CMA website and social media pages. 

To ensure we hear and acknowledge all queries and feedback in relation to the survey, Mallee CMA has established a dedicated project team to resource community outreach. 

The AEM technology has long been used to survey the salinity levels of soil in irrigation regions. 

In regions like the  Mallee where sunshine is abundant, and the soil is ideal for horticultural development, the impact of not adequately managing effects of irrigation on salinity correctly can be costly to both the immediate local area and downstream users. With plant productivity, infrastructure, soil viability, floodplains, and rivers being impacted.

Since the last groundwater survey of the region in 2007, the land area under irrigation has increased by 42% meaning there is a large area of land that has not been surveyed and there is very little data. 

The result of the 2023 survey will not only identify salinity impacts associated with new irrigation development but will also serve as a benchmark for future surveys and assessments. 

The groundwater AEM Survey and the development of final products will be funded from Mallee Salinity Impact Charges which are generated when a new water-use licence (WUL) is created or an existing water-use licence is varied to allow for an
increase in annual use limit (ML/AUL). 

The purpose of the charge is for the WUL holder to contribute towards the cost of works or measure to mitigate or offset the salinity impact of irrigation. The responsibility for managing and mitigating irrigation induced salinity has been delegated to the Mallee CMA by Ministerial Instruments.

In 2019-20, Mallee CMA commissioned a business case to scope groundwater survey options and assess the value of these options to support the management and mitigation of salinity impacts from irrigation, and to identify changes in salt distribution compared to previous surveys.  

Based on the business case recommendations, the Mallee CMA committed to develop the detailed design of the survey and complimenting project management processes. 

The business case proposed a groundwater AEM survey be conducted in 2023, covering the full extent of the current and proposed  Mallee irrigation area along the Murray River corridor and associated floodplains from Nyah to the South Australian border.

AEM is the right technology to use because it is non-destructive, time and cost effective compared with a drilling program that would provide the same amount of rigour and certainty to inform the salinity impacts arising from irrigation activity in our region.

Data collected and collated throughout the groundwater AEM Survey Project will provide
Mallee CMA with integral information on:

  • Spatial coverages of the salinity in the soil and groundwater in areas of irrigation and groundwater discharge, including floodplains, and a comparison to previously mapped salinity distributions
  • Spatial coverages of aquitards under areas of irrigation (which will help to quantify recharge processes) and the floodplain (for an improved understanding of salt mobilisation processes)
  • Spatial coverages of riverbed conductivity and near-river salinity to assist with BSM salinity accounting obligations
  • Improved hydro-stratigraphic coverages to inform salinity risk assessments, salt inception scheme operations and environmental watering activities
  • Information to guide new irrigation developments away from areas of high impact
  • Information to assist in mitigating and offsetting salinity impacts to land as required under stage legislation 
  • Spatial coverages of perched water tables in irrigation areas
  • Spatial coverage of areas of freshening groundwater due to irrigation recharge 
  • Spatial coverages of areas of inland groundwater discharge 

Mallee CMA is commissioning a groundwater Airborne Electromagnetic Survey – or AEM, which will provide vital insight into the salination levels in the groundwater throughout the Mallee irrigation region.

The groundwater survey involves a low-flying helicopter with transmitter and receiver technology suspended from the undercarriage flying across the identified area of land collecting important data on salinity levels in the groundwater to inform best practice irrigation and horticulture activities in the local and downstream environments. 

The groundwater project is a part of Mallee CMA’s regulatory obligation to ensure we are implementing ways to mitigate any risk associated with irrigation and development, to further inform growers in the region. 

The groundwater survey will take 3-4 months to complete and presents no risk to the community or the environment, and although there will be noise associated with the helicopter and the possibility of dust, it’s an exciting and educational activity that aids in how we take care of our river and water and wetland systems, land, and environment.

The last groundwater  survey of the area was done in 2007, since then the area to be surveyed has expanded by 42% meaning the data collected will be the first of its kind and continue to assist to inform irrigation and horticulture in the region for years to come.

For additional information:

Groundwater Survey Project Management Team  

Phone: 03 50018 600