Seawater intrusion monitoring underway in Lower Limestone Coast

Groundwater monitoring improvements are underway in the Lower Limestone Coast. The improvements will assist in the detection of changes in the underground seawater-freshwater interface to inform the upcoming review of the Lower Limestone Coast Water Allocation Plan review being undertaken by the Limestone Coast Landscape Board.

The Department for Environment and Water (DEW) is upgrading its groundwater monitoring network in the coastal region south of Mount Gambier.

A series of new monitoring wells are being drilled more than 100m below ground to monitor the aquifer at the depths often used for irrigation.

The drilling is anticipated to be completed by late June-early July 2022. Five wells have already been completed with two further wells to be constructed.

DEW Director for Water Science and Monitoring, Neil Power said that these wells are aimed at improving the ability to monitor and detect any changes in the seawater-freshwater interface that occurs naturally in coastal aquifers to detect any change in the location of interface, which may indicate potential seawater intrusion risk.

Groundwater resources in this area support extensive irrigated primary production, social assets and iconic sites such as Piccaninnie Ponds.

However, declines in groundwater levels in recent decades have raised the risk associated with the potential for seawater intrusion which could impact primary production and the environment.

“The area south of Mount Gambier has a unique combination of rich and productive agricultural land intermingled with incredibly important environmental assets. Additional monitoring in this area will ensure we can manage the risks of sea water intrusion,” said Limestone Coast Landscape Board Chair Penny Schulz.

“Geophysical surveys and drilling records show seawater present in the Limestone aquifer up to 1.2 km inland near Eight Mile Creek, at a depth of 158 m. The seawater-freshwater interface has been identified in a few other observation wells; however, the spatial distribution of the interface and its relationship with aquifer sub-units is not known,” said Mr Power.

“Overall the work will help identify risks and opportunities in the groundwater resource, and inform future management review,” he said.

The Limestone Coast Landscape Board leads water resource management in the region while DEW is the lead agency for monitoring of the prescribed groundwater resources.

The Department uses the water monitoring information to better understand the quantity, quality, location, trends and condition of our water resources.

For further information email Groundwater@sa.gov.au or visit http://www.environment.sa.gov.au/managing-natural-resources/water-resources/monitoring/about/groundwater-monitoring