An Arrowtown woman is taking the Queenstown Lakes District Council (QLDC) to task for a delay in issuing a public advisory about high levels of E. coli bacteria in Lake Hayes.

Routine water sampling at the lake's northern end on Monday by the Otago Regional Council returned results on Wednesday showing levels of E. coli more than four times national guidelines for safe swimming.

But the QLDC council did not issue an advisory until after Thursday afternoon, shortly after the Otago Daily Times contacted the regional council about the issue.

Octogenarian Jocelyn Robertson says she learned of the high E.coli levels earlier that day from a Facebook post by another Arrowtown resident, whom she presumes saw an advisory on the Land Air Water Aotearoa (Lawa) website.

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She and two friends of similar age had swum in the lake on Monday and Wednesday, but cancelled their Thursday swim as a result.

Mrs Robertson said the alert should have gone out on Wednesday, as soon as the QLDC got the results.

"When we were swimming on Wednesday there was quite a number of people in the lake, including children."

It was fortunate she and her friends always kept their heads out of the water, "but there were people there really swimming".

Although she could understand a delay in getting warning signs up, it should not have taken the QLDC another 24 hours to inform the public.

"It's just not good enough."

She received three texts from the council yesterday about closed roads in Arrowtown and wondered, "Why can't they do the same thing about water quality?"

The ORC needed to test its water samples more quickly, she said.

The council's media statement on Thursday said sampling at Mill Creek Shallows showed levels at 2420 E. coli per 100ml.

Government water quality guidelines for recreational swimming say water with more than 550 E. coli per 100ml is a potential health risk.

QLDC communications adviser Campbell Weal confirmed it received the first test results on Wednesday, but did not explain the delay issuing the advisory.

Test results could take between 24 and 40 hours after a sample. Past experience indicated E. coli results were high after a decent rainfall event, and people should avoid swimming for up to three days after such an event, he said.

Daily testing will be carried out at the site until the levels have reduced sufficiently.
The ORC did not respond to a request for comment by deadline.

guy.williams@odt.co.nz