Whether Taranaki's top freshwater recreational spots are safe for swimming depends on how the data are interpreted.
The Taranaki Regional Council says the water quality is the best it has been for a decade. But the Environment Ministry says "Swim at your peril".
Both organisations are using the same figures.
The TRC regularly tests the region's waterways over the summer months and provides the results to the ministry.
The ministry uses the results in its annual Recreational Water Quality Indicator, which was released this month. It graded the region's freshwater swimming spots as poor or very poor. In other words - don't swim there.
TRC director environment quality Gary Bedford said the ministry had the information on the actual water quality but was not releasing it.
"Part of our annoyance is "We gave you our actual data. Why didn't you publicise that?'," he said. There were national guidelines around recreational water quality, Mr Bedford said.
"Shouldn't that be where you start in terms of telling people whether it's safe to swim or not?"
The data supplied to the ministry showed compliance with the guidelines, but the gradings used in the report were based on hypothetical risk analysis for water quality based on surrounding land use.
"The issue we have is that the gradings start on the presupposition that if you are an intensively farmed area, like Taranaki with dairying, then the water can't possibly be safe to swim in . . . so regardless of what the real water quality is, the only grading we can assign is poor or very poor. We think this is ridiculous," Mr Bedford said.
The TRC had been urging the ministry for more than six years to change the way it graded the rivers.
"Since 2005 we have been trying to have a constructive discussion with them about our reservations about the grading system. The latest discussion is because they have made a big thing about the grading system instead of the results."
Recently the ministry agreed to a review on the gradings, but had deferred it.
Environment Ministry information directorate manager Tom Bowen said the ministry moved to the beach grading system because it was confident it was the best available methodology to convey risks to public health.
"Beach gradings are underpinned by the Recreational Water Quality Guidelines which were developed in conjunction with the Ministry of Health. They were developed using best national and international science expertise, over an extensive period of consultation," he said.
Mr Bowen said many regional councils have been using the gradings and most supported the ministry's use of the system.
"Taranaki aside, concerns raised with the ministry have not been about the beach grading system itself [microbial assessment and sanitary inspection], but on the level of guidance provided to implement it.
"This is still on the ministry's work programme."
The methodology required councils to physically monitor sites for E.Coli levels and identify and assess other risk factors present in the catchment, he said.
"A sanitary inspection is necessary because monitoring E.coli on its own does not provide an adequate indication of public health risk."
It added important information about the sources of other pathogens, and so combining that information with E.coli measurements gave a more robust indication of the health risk, he said.
- © Fairfax NZ News
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