ANALYSIS: Chamberlains Ford on Canterbury's Selwyn River used to be a swimming hole, but head there today with your togs on and you'll be disappointed.

It has all but withered into a puddle, filled with slime. There are car parks in Christchurch with more impressive swimming holes.

But under the new freshwater guidelines announced by the Government on Thursday, Chamberlains Ford would get a pass mark.

On the interactive maps the Government released alongside the announcement, its quality for swimming is marked as "good", despite the (seemingly limiting) fact there's no water to swim in.

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It gets stranger: According to those same maps, the Opihi River near Timaru would get an 'A' grade under the new guidelines, the highest mark possible for swimming quality.

As of Thursday afternoon, every monitored swimming site on the Opihi River has a toxic algae warning.

It means that a river graded with the highest quality for swimming is simultaneously too dangerous to swim in. How does that work?

It speaks to the slippery politics around the word "swimmable", and how the word is being used in seemingly imprecise ways.

From the press release, the Government's announcement – that by 2040, 90 per cent of water bodies need to meet bottom-line water quality guidelines for swimming – sounds like a no-brainer.

But instead of being hailed by environmental groups as an ambitious turnaround, it was publicly called a "fraud" and "disgusting". Privately, the adjectives were less polite.

The critics' chief concern is that the Government has now defined "swimmable" in a way that is vastly different from what they think a regular person would deem to be "swimmable".

The Government's "swimmable" standard now has a number attached – 540 E coli per 100 millilitres of water. If a river meets that standard 80 per cent of the time, it gets a tick.

Up until now, most councils have determined recreational water quality using Ministry of Health guidelines, which don't define the term "swimmable" but suggest it to be much stricter.

Those guidelines state that if you swim somewhere with an E coli level of 550 per 100mls, you have a one in 20 chance of contracting campylobacter, a nasty gastro illness.

That is essentially what the new bottom line standard is – a one in 20 chance of getting sick. That is what "swimmable" now means.

As freshwater ecologist Dr Mike Joy told RNZ on Thursday, if one in every 20 diners at a restaurant contracted a gastro illness, it probably wouldn't pass a health inspection, let alone get an A-grade.

"Imagine going into a restaurant with 20 mates and knowing one of them would get sick.

Joy, a senior lecturer at Massey University in Palmerston North, said the Government has simply "shifted the goalposts" for water quality.

Whereas the previous measure for water deemed to be safe to drink and swim in was 260 E coli units per 100 millilitres, that had now been pushed out to 540 units.

"All they've done is shifted the threshold and they've done that by shifting the baseline," Joy said.

"What would have required a sign to be put up as a warning is now considered to be a swimmable river.

"They've tried to pull a 'swifty' on the people of New Zealand, and it hasn't worked for them because we've called them out on it."

"We want to have rivers we can swim in. We're not asking for much, just what we had a few years ago."

The other issue pointed out by critics is that E coli is just one possible measure of swimmability, which is where examples such as Chamberlains Ford and the Opihi River come in.

They are unswimmable for different reasons – the latter because of toxic algal blooms fuelled by dry conditions and nitrogen levels, the former because it doesn't have any water in it – yet both are technically "swimmable" because they pass the E coli test.

Nasties such as nitrates and phosphorous are important indicators of water health, influencing the growth of algae, which affect swimmability too. The new guidelines will require councils to take these into account, but what that actually means is unclear.

There are other things the Government announced – money towards freshwater improvement and changes to stock exclusion rules are a couple – but it's difficult to get past the politicised nature of the word "swimmable", and how it may soon have a policy definition vastly different from how others would define it.

The fear is the Government will achieve its goal, in which 90 per cent of the country's water bodies are indeed "swimmable". They just might not have any water in them.

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