Marlborough’s waterways have mostly been given a clean bill of health.

Each summer eight beaches and eight river swimming sites around the province were monitored with weekly samples analysed to assess health risk to swimmers.

Sites include Anakiwa, Picton Foreshore, Waikawa Foreshore, Te Hoiere/Pelorus River at Pelorus Bridge and the Waihopai River at Craiglochart.

Council environmental scientist Steffi Henkel told the Environment Committee yesterday that 80 per cent of samples fell into the green, low-risk category which was considered safe for swimming.

“Higher levels of bacteria were mostly caused by surface runoff from rainfall,” she said.

“Water quality in Marlborough is generally good but on rare occasions waterborne pathogens can make swimmers sick, which is why regular sampling of recreational water is carried out.”

Individual sampling showed only information for a specific time and date; therefore data was combined over several summers and analysed.

Collated data showed a marked improvement at three sites - Momorangi Bay, Picton and Totara Flat, Steffi said.

“The Rai River at Rai Falls often had the highest bacteria levels but an assessment over 10 years showed significant reductions. It’s important to recognise the continued investment by the farming community in reducing stock access to waterways there.”

The Te Hoiere Catchment Restoration Project aimed to improve water quality further.

Likewise, trend analysis showed a significant reduction in bacteria concentrations in the Taylor River at Riverside, due mainly to sewage infrastructure repairs since the Kaikōura earthquake in November 2016.

Ngakuta Bay and neighbouring Governors Bay showed notable increases in bacteria concentrations and will be further investigated so action could be taken to improve water quality. Ms Henkel said the Governors Bay levels indicated visiting boats as a potential source.

Sites will continue to be monitored next summer with the inclusion of Okiwi Bay and Mistletoe Bay which were omitted this season due to road closures.

Further information: https://www.lawa.org.nz/explore-data/swimming/

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