Castlecliff Beach the only swimming spot in Whanganui with long-term good-quality water

Castlecliff Beach is the only swimming spot in Whanganui with long-term good-quality water. Photo / Bevan Conley

Castlecliff Beach is currently the only swimming spot in the Whanganui district with good water quality, according to Land Air Water Aotearoa (LAWA).

The results are based on monitoring data from previous summers, with four rankings; excellent, good, fair and poor.

Castlecliff Beach is the only swim spot in the Whanganui District with good long-term water quality, meaning there’s a less than 5 per cent risk of illness from contact with the water.

Two other spots in Whanganui are listed as having fair quality water, Lake Wiritoa and South Beach.

The majority of swimming locations in Whanganui are listed as having poor-quality water, including Kai Iwi Beach and the Mowhanau Stream, Lake Dudding, and the Whanganui River at the Town Bridge, Union Boat Club and Mosquito Point.

This means swimmers have an estimated more than 5 per cent risk of Campylobacter infection at rivers and lakes, or a more than 10 per cent risk of illness from contact with the water at beaches.

Horizons Regional Council monitors the water quality in the district, and environmental monitoring scientist Ian Hurst said recreational sampling programme runs on a weekly basis with samples being taken from Monday to Wednesday.

This sampling takes place no matter the weather, which can lead to sampling swim spots during rainfall events which often results in there being more faecal bacteria in the water.

“Long-term grades can be affected by a small number of samples taken when there is high faecal indicator bacteria. In most cases, this is related to a rainfall event,” he said.

The long-term grades also represent a near worst-case risk to swimming over the monitoring period, as it can’t be limited when people swim.

Castlecliff Beach likely had particularly high-quality water because of its location.

Coastal beach sites within the region historically have always had overall better recreational water quality than river sites, Hurst said.

“Furthermore, coastal sites that are away from the regular influence of river systems tend to perform even better.

“Castlecliff Beach happens to meet both of the aforementioned criteria and therefore tends to produce good quality results,” Hurst said.

However, like river sites, beaches were also prone to quick changes in water quality due to recent weather, so it was still worth checking LAWA and local conditions before swimming.

Horizon’s general approach when there had been persistently high faecal bacteria in a swimming spot was to identify the source of the bacteria to address it.

“For example, targeting intervention from our non-regulatory teams to establish stock exclusion and riparian planting.”

Since swim spot monitoring began the council and landowners have planted 115,000 riparian plants and fenced 432,600 metres of stream and riparian fencing in the Whanganui catchment alone.

“These measures are proven to help improve the quality of water in the catchment.”

Horizons swim spot monitoring season began earlier in November.

Hurst said it was hard to predict the outcomes of this year’s monitoring because samples were highly influenced by weather patterns, especially rainfall.

“However, if the region experiences less rainfall than last year we would expect an improvement in faecal indicator values but this may not change the long-term grade,” he said.

The council were also currently reviewing the One Plan, the combined regional policy statement and regional plan, to implement the National Policy Statement for Freshwater which includes components around suitably.

Finn Williams is a multimedia journalist for the Whanganui Chronicle. He joined the Chronicle in early 2022 and regularly covers stories about business, events and emergencies. He also enjoys writing opinion columns on whatever interests him.