Warning of Wānaka E.coli risk after heavy rain

Water testing in Lake Wānaka this week has shown E. coli levels high enough to put the health of lake users at risk.

'No swimming signs' erected at Roys Bay over the weekend as heavy rain fell across much of Otago have now come down.

However Queenstown Lakes District Council infrastructure operations manager Simon Mason confirms water taken from the lake by council contractors earlier tested posted for unsafe levels of E. coli.

"Veolia undertook sampling in response to reports that soapy-looking water was entering the lake from a creek near the 'Wānaka tree'," he says.

"On arrival they couldn’t detect any visible signs of pollution but collected samples as a precaution."

He says the public health warning signs were required as the testing revealed levels of the bacteria above the normal swimming limit, and further water samples from the lake were then tested.

"Results from testing that occurred after the rain abated came back clear."

Despite the seemingly pristine appeal of the Southern Lakes waterways, Mr Mason says local authorities including the Otago Regional Council and Land, Air, Water Aotearoa recommend not swimming in them after persistent rain events.

"Given the weather at the time of the report and over previous days, it’s likely that this was indeed the cause (of the Roys Bay pollution), although the levels detected did not indicate gross contamination."

He says in general the local council does not conduct regular monitoring of lake water.

"This is the responsibility of ORC as part of its recreational water monitoring programme. QLDC only conducts event-based sampling, as in this case."

Wai Wānaka is making the most of the incident to highlight positive action community members can take to improve water quality in their neighbourhoods.

"This week's no-swim warning highlights exactly why we began the 'Adopt a Drain' programme," it says in a shout to on social media.

"Heavy rainfall brings stormwater pollution into local lakes, but together we can take action to stop it at the source. Uniting as a community is key when it comes to future generations being able to swim and enjoy the deepwater lakes of our communities."

Learn more about the organisation's 'Adopt a Drain' programme here.

Main image (Background/Pixabay): 'No swimming signs' were erected on a beach of Lake Wānaka near the iconic 'Wānaka tree' on Sunday, October 6, 2024.