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

Data from Land Air Water Aotearoa (LAWA) shows seven Bay swimming spots, including Kaiate Falls in Welcome Bay, have warnings advising people to stay out of the water.

Other "unsafe" areas are Pukehina at Waihī Estuary boat ramp, Lake Ōkaro, Lake Rotoehu at Otautu Bay and Kennedy Bay, Ngongotahā Stream, Utuhina Stream and Uretara River.

Tauranga woman Michelle Lee visited Kaiate Falls at the weekend, undeterred by the health warning.

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"I had wanted to go for a while so decided to take the kids there. It was bustling with people and such a beautiful spot I'm not surprised.

A sign advising against swimming at the entrance to Kaiate Falls. Photo / George Novak
A sign advising against swimming at the entrance to Kaiate Falls. Photo / George Novak

"There were warning signs but we took the risk. We came home and had no issues with being sick at all."

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.

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".

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 we issue a warning".

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

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

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

"In some of our hot-spots such as at Uretara Stream and McLaren Falls, natural sources of E.coli bacteria such as from birdlife may be contributing to the problem."

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

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

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 cannot see your toes in calf-deep water.

More than $30 million was spent annually toward improving the Bay's water quality, including work with landowners and community groups to identify and mitigate E. coli hotspots such as Kaiate Falls, Uretara Stream and Waiōtahe Estuary.

"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 science research began this summer to isolate sources of bacterial contamination frequently affecting popular swim spots in the upper Wairoa River including McLaren Falls and the Waitetī Stream (near Ngongotahā).

Federated Farmers Bay of Plenty president Darryl Jensen 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.

Jensen fondly recalled visiting Little Waihī as a child and swimming in the estuary. These days the water, like at Kaiate Falls, is "unsafe".

"We are using good science as to why this is ... we want it back to the way it was 20 to 30 years ago."