Dry conditions lead to drop in shallow groundwater

Groundwater levels have dropped across the region due to prolonged dry conditions in 2018- 19, Goulburn-Murray Water’s (GMW) annual water table study shows.

The study monitors more than 1000 observation bores and allows GMW to map shallow groundwater level changes across the Shepparton Irrigation Region (SIR), which includes the Murray Valley, Shepparton, Central Goulburn and Rochester irrigation areas.

As part of the study, groundwater has been mapped in depth segments of 0-1m, 1-2m and 2-3m from the ground surface. GMW uses water table monitoring as a key way of informing salinity management in the region.

GMW uses monthly groundwater levels to govern the operation of its Public Groundwater Pump network. This network helps to provide salinity mitigation to high risk areas across the SIR.

GMW Manager Drainage Systems Simon Cowan said the reduction in the area showing shallow groundwater was linked to below average annual rainfall over the past 18 months.

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

Shallow groundwater levels are now at a level similar to those observed during the Millennium Drought.

“Dry conditions have an obvious direct effect on water table 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.”

Goulburn Broken CMA Manager Sustainable Irrigation 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 water table study has also helped us with the planning and development of salinity management programs such as surface drainage, water table management and irrigation efficiency.”

The annual August Water Table Study is jointly funded by the Goulburn Broken CMA and GMW. Water table maps dating back to the mid-1980s can be found here.