Otago rivers by and large ‘in really good state’

A container sits in Otokia Creek at Dunedin’s Brighton Beach as the creek goes to sea. The area is the only coastal site monitored by the Otago Regional Council that has a long-term grade of "poor" due to elevated bacteria levels. Previous investigations have identified avian sources for the contamination. There are an additional four freshwater sites with "poor" long-term grades, the council says. PHOTO: GERARD O’BRIEN

Otago Regional Council science and resilience committee co-chairman Gary Kelliher said this year’s recreational water quality annual report showed the region had healthy waterways.

"By and large our rivers are in a really good state and we are able to enjoy them generally most of the time.

"So I think it’s a good report card - I would hope that would be the case."

The council’s contact recreation monitoring programme assessed recreational water quality at swimming spots weekly between December and March each year, a report to the committee said.

Faecal bacteria Escherichia coli, at freshwater sites, and enterococci, at coastal sites, were measured as an indication of the presence of pathogens that could cause illness in swimmers.

Last summer, 509 routine samples were taken and analysed for 32 sites - 93% of the results showed the water was safe for swimming at the time the sample was taken, the report said.

For 14 samples across 12 sites, bacteria concentrations indicated the site was unsafe to swim at at the time of sampling and a health warning was issued, it said.

Another 17 results across seven sites met the criteria for the council to advise caution, it said.

Long-term E. coli grades for freshwater sites showed 67% of freshwater swimming spots were either "excellent" or "good".

Four sites were graded as "poor" - the Taieri River at Waipiata, the Taieri River at Outram, the Waikouaiti River at Bucklands and the Manuherikia River at Shaky Bridge.

Among coastal sites, 88% were graded "excellent/very good", or "good" and just one site, Otokia Creek at Brighton, was graded "poor".

Previous investigations had identified avian sources for the contamination at Otokia Creek, the report said.

The long-term grade for the Pacific Ocean at Tomahawk Beach west improved from "fair" to "good".

The site was monitored by the Dunedin City Council as part of the consent requirements for the Tahuna wastewater treatment plant, the report said.

"The grade change can be attributed to several elevated results in the 2019-20 season not being included in the latest five-year period, and two years with no exceedances in the current period," it said.

— APL