Council Receives Results Of Lake Wyangan Investigation

Here's what it said


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After a significant fish death occurred on 23 and 24 May 2020, an independent investigation was undertaken, with Griffith City Council receiving the results on Wednesday 8 July 2020.

The event was reported to the NSW Department of Primary Industries (DPI) Fisheries and the Environmental Protection Authority (EPA).

Griffith Mayor, Councillor John Dal Broi said the report has ruled out localised pollution or pesticide as a cause of the fish deaths, and welcomed the findings of the report, adding that Council will now work toward implementing solutions to the issues raised.

“The evidence suggests that the storm event on 29 April 2020 created a drop in temperature of around 6-7C, causing significant stress to the native fish in the Lake, such as the Bony Bream, Murray Cod, and Golden Perch,” said Councillor Dal Broi.

“The drop in temperature when combined with the other factors outlined within the independent report (including high pH levels, high salinity, high hardness and disturbance of sediment in the Lake), created an environment which led to the fish kill during May.”

Lake Wyangan is the site of an old gypsum mine, a fact the consultant states contributes to the high salinity, pH and hardness of the water experienced in the Lake.

In January, Council added approximately 900 mg/L to Lake Wyangan which had no effect on the fish at the time, with all the factors the same as the May event including comparable water levels.

“The only factor which changed during the May event was the water temperature – during January the temperature stayed high given it was summer, however following the storm event in April a cold snap dropped the water temperature over a period of 2-3 days significantly,” he said.

“The storm event not only dropped the temperature of the water, but potentially disturbed the acid sulphate soil in the sediment on the Lake bed impacting oxygen levels and creating the conditions which led to this tragic event.”

“Our Local State Member made unsubstantiated allegations of mismanagement early in this investigation, however the independent analysis demonstrates her comments were unfounded.”

Griffith City Council will now begin testing the sediment profile and salinity, with the consultant supporting the work and testing already being undertaken, including the installation of sediment ponds and the creation of wetlands.

For more information on the independent findings or to read the report, you can visitthe Department of Primary Industries website at www.dpi.nsw.gov.au

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9 July 2020




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