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Water quality generally good over summer

21 Apr 2021, 7:14 AM

Investigations show water quality at most popular Northland swim spots – especially those on the coast – met swimming guidelines over summer, with birds and stock a common link to those which didn’t.

The Northland Regional Council carried out hundreds of samples at 58 sites - 16 freshwater sites and 42 coastal – between 07 December last year and 08 March 2021.

Justin Blaikie, chair of the council’s Water and Land Working Party, says the council tests for faecal bacteria, used to gauge the risks of contracting gastrointestinal and other infections while using beaches, rivers and lakes for swimming, water sports and other forms of recreation.

The council had found that in coastal areas 98 percent of the 577 samples taken at 48 sites had complied with the Ministry for the Environment’s Recreational Bathing guidelines; just nine samples (or two percent) failing to comply.

Subsequent microbial source tracking at six different sites had revealed birds as the major source of the coastal faecal contamination.

Councillor Blaikie says non-compliance was higher at freshwater spots with 28 non-compliant samples (12%) of the 234 taken.

“Most of the non-complaint results were ‘one offs’ for some sites, which correlated with a rainfall event 72 hours prior to sampling.”

However, Victoria River at the DOC Reserve on the north side of the Mangamukas and the Tirohanga Stream at Kawakawa had exceeded guidelines numerous times.

Twenty-eight samples had been taken from 12 different sites for microbial source tracking, which generally identified stock and bird sources as major contributors of any contamination.

“At the Victoria River however, human sources were reported on a number of occasions, but unfortunately were unable to be traced to their source.”

“The full 2020/21 swimming water quality results are still to be finalised, however, weekly monitoring results for all swimming sites can be found on the LAWA website: www.lawa.org.nz/explore-data/swimming

Councillor Blaikie says as usual over summer, results were also regularly forwarded to the Whangarei, Far North and Kaipara District Councils, the Northland District Health Board (DHB) and other interested parties.

“We let the health board and relevant district council know of any results showing elevated bacterial levels, typically within 48 hours, as part of a jointly agreed protocol and it’s their responsibility to undertake follow-up sampling and other action.

That action can include public warnings not to swim or gather shellfish and putting up permanent warning signs at the worst sites.

Councillor Blaikie says yearly results can vary quite considerably, largely due to whether there’s a dry or relatively wet summer.

“Council always advises people not to swim for two or three days after heavy rain, which can carry run-off from land, or if there are warning signs indicating unsafe water.”

“Also a good useful rule of thumb is not to swim if the water looks dirty or murky, smells or has scum on its surface and also look out for, or consider, any potential sources of contamination, both nearby and upstream.”

He says water quality concerns can be reported to council’s freephone 24/7 Environmental Hotline on (0800) 504 639.