Some of the Bay of Plenty's most popular swimming spots are considered too dangerous to swim in but that has not stopped hoards of people going for a dip in contaminated waters this summer.

Data from Land Air Water Aotearoa (LAWA) shows seven Bay swimming spots, including the Ngongotahā and Utuhina streams have warnings advising people to stay out of the water to prevent contamination.

Other "unsafe" areas are Pukehina at Waihī Estuary boat ramp, Lake Ōkaro, Lake Rotoehu at Otautu Bay and Kennedy Bay, Kaiate Falls in Welcome Bay and Uretara River.

Tukaki Henare says he has swum in Rotorua streams all his life and that won't change. Photo / Ben Fraser
Tukaki Henare says he has swum in Rotorua streams all his life and that won't change. Photo / Ben Fraser

Warnings are issued by Toi Te Ora Public Health which, with Bay of Plenty Regional Council, monitors the region's waterways for bacteria levels such as E. coli within every two weeks. Signs are placed at the entrance to each "unsafe" site.

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However, chief medical officer of health Dr Phil Shoemack said despite the warnings "we would not close an area. It's similar to warnings on packets of tobacco or consumption of alcohol".

Rotorua man Tukaki Henare said he wasn't aware the Ngongotahā Stream was unsafe to swim in and said it wouldn't change his swimming habits.

"I'm 44 and I've swum in this all my life. We used to swim in the lake [Rotorua] abundantly but it seems to me now people just swim anywhere.

"The first choice for me would be the streams. They are supposed to be fresh.

 The Ngongotahā Stream is among seven contaminated waterways in the Bay of Plenty. Photo / Ben Fraser
The Ngongotahā Stream is among seven contaminated waterways in the Bay of Plenty. Photo / Ben Fraser

"I don't think many people would think twice about jumping in the stream unless you had warning signs."

Henare questioned why people caught and ate fish from the stream if it was considered unsafe.

Ministry for the Environment guidelines dictate a threshold regional authorities compare their water contamination levels against. Local waterways are regularly tested by councils and if contamination levels are above the threshold then a warning is issued.

"It's basically helping people make their own informed judgment," Shoemack said.

People swimming in contaminated waters risk contracting gastrointestinal illness, conjunctivitis and skin infections, he said.

Bay of Plenty Regional Council's Chris Ingle said water contamination could come from inappropriate use of stormwater drains, poorly maintained septic tank systems, rainwater run-off from urban areas, roads, and farmland; "and the occasional sewerage overflow – usually caused by people flushing inappropriate items down the toilet and blocking up the sewerage network".

Chief medical officer of health Dr Phil Shoemack says people can make up their own minds on health warnings of swimming spots. Photo / file
Chief medical officer of health Dr Phil Shoemack says people can make up their own minds on health warnings of swimming spots. Photo / file

Ingle said there was growing evidence that in some spots, E. coli might be building up over time in streambed sediments "and being re-mobilised during rain events".

Both Ingle and Shoemack said regardless of health warnings, people should avoid swimming for at least two to three days after heavy or prolonged rain - especially if you can't see your toes in calf-deep water.

More than $30 million was spent annually toward improving the Bay of Plenty's water quality, including work with landowners and community groups to identify and mitigate E. coli hotspots.

"Through [the] council's work with Fonterra and local landowners over the past year, 16 Farm Environment Plans are now being put into action in the Waiōtahe catchment."

Ingle said new research began this summer to isolate sources of bacterial contamination frequently affecting popular swim spots in the upper Wairoa River and the Waitetī Stream.

Federated Farmers Bay of Plenty president Darryl Jensen said the industry was working closely with authorities and had embraced the need to protect local waterways. However, there was no "quick fix" and it would take time and effort to get results - but it was worth it.

"We want it back to the way it was 20 to 30 years ago."