Lake Cathie hits trigger point for artificial opening

Area west of the Kenwood Drive bridge at Lake Cathie. Photo: supplied.
Area west of the Kenwood Drive bridge at Lake Cathie. Photo: supplied.

Port Macquarie-Hastings Council has no plans to open Lake Cathie to the ocean despite the trigger point being reached for an artificial opening.

Port Macquarie-Hastings Council director Melissa Watkins said the Lake Cathie Opening Strategy contains several opening triggers. 

“One such trigger is when the water level is less than 0.2m AHD and salinity is greater than 40 ppt,” she said.

“The current water level is 0.05m AHD and salinity is between 40 and 42 ppt, therefore a lake opening trigger has been reached.”

However the lake will not be opened by council due to several risks associated with the action.

Ms Watkins said the risks include low lake water levels which limit the success of an excavated channel remaining open, the likelihood of excessive sand build up in the recently dredged area and potential risk for red weed to enter and become stuck in the lake should it naturally close quickly.

Ms Watkins said another risk is the likelihood of insufficient flushing of the lake and system shock when very cold ocean water meets warm lake water.

“This is likely to have adverse effects on the ecology of the lake,” she said. 

The Lake Cathie Opening Strategy indicates that when opening triggers are reached the lake should be opened ‘during optimum conditions’.

“Based on the risks and consultation with other government agencies, council has made the assessment that optimum conditions do not currently exist, and any opening of the lake at this time could result in adverse impact to the recreational amenity and  ecology of the lake,” Ms Watkins said. 

A Lake Cathie resident has questioned why the lake hasn’t been opened given the ‘critically low water level’.

Richard Faddy said he went for a walk with a friend to look at the area west of the Kenwood Drive bridge and was concerned to see the effect of the current low water level and smell of rotting fish.

“It would appear that now all the marine life of the lake is concentrated in the small lagoon,” he said. 

“With no remedial action will result in everything contained there will be lost.”

Richard said he understands there is an opening policy the Port Macquarie-Hastings Council complies with.

“As council just spent some $300,000 on foreshore rectification you would think that the investment of a small amount for the opening to save the lake would be well justified,” he said. 

Ms Watkins said while the water levels are low, there is no evidence of significant water quality issues and the lake remains safe for recreational use.

Council will continue to undertake water quality monitoring on a weekly basis until the end of February 2019, and review lake conditions in the future.

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