Groundwater levels dropping in dry conditions

By Jamie Salter

Groundwater levels have dropped across the region due to prolonged dry conditions from 2018 to 2019.

Goulburn-Murray Water drainage systems manager Simon Cowan said groundwater was linked to below average annual rainfall over the past 18 months.

“We’ve seen a decrease in the area associated with the 0-1 m and 1-2 m depth ranges compared to 2016, the last time we had heavy rain,” Mr Cowan said.

G-MW's annual watertable study monitored more than 1000 observation bores and mapped shallow groundwater level changes across the Shepparton Irrigation Region, which includes the Murray Valley, Shepparton, Central Goulburn and Rochester irrigation areas.

“Dry conditions have an obvious direct effect on watertable levels but it’s important we don’t become complacent,” Mr Cowan said.

“That’s why monitoring is so important — particularly in the area between Lake Cooper and Waranga Basin, which tends to show the greatest annual fluctuations.”

Groundwater was mapped in depth segments of 0-1 m, 1-2 m and 2-3 m from the ground surface to inform salinity management in the region.

Monthly groundwater levels were used to govern the operation of the G-MW public groundwater pump network, which helps to provide salinity mitigation to high risk areas across the Shepparton Irrigation Region.

Goulburn Broken Catchment Management Authority sustainable irrigation manager Carl Walters said the mapping project had been undertaken since the early 1980s.

“Victoria’s recent presentation to the MDBA Salinity Audit Group demonstrated that we are managing our salinity responsibilities very well,” Mr Walters said.

“This mapping has been a significant and simple tool to help landholders and the community understand what is happening with the rise and fall of the threat of salinity over time.”

“As rising groundwater is often linked to an increased risk of salinity, the annual watertable study has also helped us with the planning and development of salinity management programs such as surface drainage, watertable management and irrigation efficiency.”

The annual August Watertable Study is jointly funded by Goulburn Broken CMA and G-MW.

Watertable maps dating back to the 1980s can be found at: www.gbcma.vic.gov.au