The alert means the water in the north lake is unsuitable for recreational or domestic use, as well as posing a threat to pets and livestock.

Blue-green algae can cause gastroenteritis, eye and skin irritations and the bacteria cannot be removed by boiling the water.

The presence of blue-green algae is monitored by Griffith City Council.

Council’s Lake Wyangan and catchment project officer Tom Ryan said despite the biovolume reading of non-toxic algae being elevated, the biovolume of potentially toxic algae species remains very low.

“We are obliged to close the Lake as a precautionary measure to ensure the health and safety of the community,” Mr Ryan said.

Earlier this year, Griffith’s councillors voted to sell 1200 megalitres of water to help fund a long term solution to reduce the occurrences of blue-green algae blooms.

Around 300 megalitres of water will be added to the lake from council’s 2018/2019 allocations.

Council is continuing to test equipment for aeration and water circulation to determine whether they are effective in reducing blue-green algae blooms in the lake.

Warning signs have been placed at Lake Wyangan, and user groups have been notified by council.

While access to the lake is restricted, the lake’s picnic area remains open.