People are being advised to avoid the Patea River in King Edward Park, after high levels of the bacteria E. coli have been detected.

Signs are up warning of the presence of the bacteria, which are an 'indicator' bacteria used to detect possible pollution. High levels of E coli are a warning that contact the water might be harmful to humans and animals.

Science adviser at the Taranaki Regional Council (TRC), James Kitto, says the discovery was the result of the regular water quality monitoring at the site undertaken by TRC.

"We discovered a high level last year on December 4, with a reading of just over the guideline of 550/100ml. We advised the Stratford District Council."

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James says while the monitoring is the responsibility of the regional council, it is the district council who then has the duty to inform the public of any public health risk through signage at the site.

Government water quality guidelines for recreational swimming areas state that less than 260 E. coli/100ml is preferred and levels below 550 E coli/100 mls are acceptable whereas water with more than 550 E. coli/100ml is considered to pose an unacceptable public health risk.

Once higher levels are detected, further testing is carried out. After the December 4 incident, the warning remained in place for a couple of days until December 6, when three more tests of the water were carried out, and came back with readings below the actionable level.

James says they prefer to test in dry weather as the rain can skew readings noticeably and more people go swimming in fine weather than in rain with rivers in flood conditions.

Between November and the end of March each year around 13 water quality tests are taken as routine at the site, with more taken if high readings are recorded, says James. He says TRC monitors water quality at 16 or 17 fresh water sites in the region and a further 12 or 13 marine sites. The Patea River Scout Den site is the only site in the Stratford District to be routinely monitored.

A reading of 1050/100ml was found on January 15, causing the sign to be put up again, with following readings showing even higher levels of 1200/100ml. James says further investigations are now being carried out, with samples also being taken from the rivers tributaries and a sample being sent to the Institute of Environmental Science and Research in Christchurch for DNA testing.

This, says James, is to identify the potential source of the bacteria, with the main three contenders being avian (birds), bovine (cows) or human. The sign remains in place until safe levels are recorded and James says people are advised to follow the advice given and refrain from swimming or fishing in the river.