LOUGH CALVERT DRAINAGE SCHEME UPDATE

Corangamite Catchment Management Authority (CMA), as the statutory manager of the Lough Calvert Drainage Scheme (LCDS), commenced releases from the Scheme on 21 July 2023.  

Releases commenced at a conservative 6ML/day to enable the wetting of the channel, infrastructure to be tested and the gauges to be calibrated.

Maintaining a conservative approach, the outlet flows were gradually increased across the week, and kept below the levels that would trigger any concerns with salinity at Winchelsea.

Rain during that first week of operations caused inflows into Lake Colac to increase and in response the Corangamite CMA increased releases to maintain lake levels while avoiding downstream impacts. This management decision successfully maintained the Lake level across the weekend. 

To support an adaptive approach to this release, Corangamite CMA has a water quality monitoring plan in place, with numerous water quality gauges that measure salinity, flow, and water level at Lake Colac, along the drainage channel and downstream along Birregurra Creek and the Barwon River. 

Last Monday, the gauges along the Barwon River at Kildean Lane and Winchelsea showed that salinity was increasing, and the outlet flows were subsequently decreased.

The Corangamite CMA further reduced releases to mitigate this increase in salinity at Winchelsea, whilst managing for downstream erosion that could result from sudden changes in flows.

Wormbete Creek and other waterways that flow into the Barwon River are contributing to high levels at Winchelsea. Site monitoring this past week at Wormbete Creek showed salinity levels above 5300 EC. Corangamite CMA is now continuing to monitor salinity in Wormbete Creek and other nearby waterways to understand how these streams contribute to salinity changes in the Barwon River at Winchelsea.

The salinity level at 9am on Monday 7^th August had reduced to 2269 EC at the Barwon River at Winchelsea.

Corangamite CMA has been advised that this recent salinity spike should not be a concern for native fish species or domestic stock. The Corangamite CMA will continue to operate the scheme flexibly in response to changing conditions. The health of the Barwon River remains a priority in how the CMA manages the scheme.

-ENDS-