Swimmability of Mowhanau stream in question, residents to discuss improvements

Linda Smith's granddaughters Paige, 9, and 12-year-old Emma were some of many children who played in Mowhanau Stream this summer. Photo / Bevan Conley

A Horizons regional councillor hopes the signs warning of the danger of swimming in the Mowhanau Stream could come down by next summer.

David Cotton, lives at the beach and said the signs can't be ignored. But he's talked to many residents about the stream and none knew of children getting sick.

"I'm not saying it doesn't happen, but it isn't common," he said.

Improving the stream's health will be a main focus of his coming year on council. There's been one meeting of local landowners, who want to form a catchment group. With fellow resident George Matthews, he plans to hold a second meeting in mid-February for anyone interested.

One of the first moves will be more sampling to find out exactly where the contamination is coming from.

Fixing it might require sediment traps in side creeks, he said, or adding more wetlands to filter the water.

Local resident Linda Smith took no notice last week as she supervised her two granddaughters.

"I get brassed off with all the PC crap that goes on," she said.

Smith has lived at Mowhanau for 25 years, and spent many a Sunday at the beach when she was growing up.

The sign warns people to keep their heads out, not to swallow the water and to wash their hands before eating.

It, and others at nearby Kai Iwi and Ototoka streams, were erected in December 2018. At that time the three streams only met New Zealand bathing standards 13, 8 and 4 per cent of the time, respectively.

Smith has never heard of anyone getting sick from the water, though she concedes there are more cows upstream these days.

A no swimming sign at Mowhanau Stream.

Horizons takes water samples from the streams every week during swimming season.

Spokeswoman Amber Garnett said the council advised against any recreational use.

"These sites have long-term notices in place, as there is a moderate to high risk of exposure for swimmers. These notices were put in place due to the high proportion of E. coli exceedances, in consultation with Public Health."

The latest results of water testing are on the Land, Air, Water Aotearoa (LAWA) website.

It says E. coli levels in the Mowhanau Stream are in the worst 25 per cent of sites.

Most of the E. coli has been sourced to cattle and sheep. The stream is also high in nitrogen and phosphorous.

Whanganui District Council was prosecuted and fined after effluent from the village's wastewater treatment plant flowed into the stream in 2017 during a power cut.

Whanganui Horizons councillor Nicola Patrick said the council had a responsibility to warn people of the health risk. It is worse in the first three days after rain in the catchment.

She said her children swam and played in the stream.

"My kids are big, healthy resilient kids. If they get a little bit sick it's not the end of the world."

But she said the high nitrogen and phosphorous levels were indicators that the stream ecosystem was unhealthy. Factors influencing it could include stock access, leaking septic tanks and bird excrement.