Canterbury's Selwyn River, at the Coes Ford bridge, full of river weed and at a low water flow.

ANALYSIS: For the first time in recent memory, political parties have been forced to reckon with a major problem: growing public concern about the state of freshwater.

It is shaping up to be a major election issue, according to prospective voters and the parties themselves.

In a pre-election survey conducted by Stuff and Massey University, the environment was deemed the issue third most likely to influence a vote, behind health and housing.

LAWRENCE SMITH/STUFF Prime Minister Bill English and Environment Minister Nick Smith announce a plan to clean up New Zealand's waterways at Riverhead, north of Auckland.

It comes after a year with multiple high-level reports pointing to pressing issues around water quality; a year where once-popular swimming holes dried up, and others languished, green and nutrient-filled.

READ MORE:

* Top scientist: Fixing freshwater issues an 'enormous challenge'

* Farming, emissions and waste putting NZ's 'green' reputation at risk, OECD says

* What are New Zealand's environmental priorities over the next 20 years?

* The environment, not agriculture is New Zealand's economic backbone

Freshwater is a nasty problem for any political party to address; firstly, for its complexity, but also because any position risks alienating large groups in what may be a tight election.

For each party, their political calculus must address the cause of pollution, without being seen as sabotaging the economy.

Each of the parties has approached the dilemma differently, and all come with their own risks and rewards.

THE 'BLUE-GREENS'

And so it begins with National, the party in which the status quo inevitably falls.

Political commentators have said the Government was caught flat-footed on water issues, particularly that of water bottling.

One thing has defined the Government's approach to water: finding a balance between economy and environment.

Pupils from Hira School in Nelson monitor water quality in the Wakapuaka River.

Throughout his tenure, Environment Minister Nick Smith has embraced the term "blue-green", as have others in the party. It captures the Government's belief in a happy marriage between economy and environment; one which some critics say needs a swift divorce.

National's signature freshwater policy is its already proposed change to the National Policy Statement for Freshwater (NPS-FW), floated with the snappier headline of making 90 per cent of waterways "swimmable" by 2040.

The policy replaces the "wadeable" bottom line with a "swimmable" bottom line, by using an E.coli measure based on time, not quantity.

CAMERON BURNELL/STUFF NZ First Leader Winston Peters has been making a play for the rural vote.

The policy immediately caused confusion, even among freshwater scientists, about whether it made the standard stricter or simply shifted the goalposts.

While batting off criticism about obfuscating the issue, the Government defended its environmental record in other ways: It has committed $100m over 10 years for freshwater restoration projects, with a further $350m in the pipeline; it introduced water metering standards to measure water usage; many councils now had water plans, which they previously had not.

However, it is a fine line to walk.

MONIQUE FOR/STUFF Gareth Morgan is leader of The Opportunities Party.

While counting off its environmental efforts on its left hand, one must not forget to look at its right.

The Government's Irrigation Acceleration Fund will grant $400m of public money in the form of loans to irrigation schemes, which in some areas will increase nitrate pollution.

It has committed to doubling the value of primary exports by 2025: Primary Industries Minister Nathan Guy recently said this needed to focus on value, not volume, as farming "had limits", but there's no mandate for that to happen.

KEVIN STENT/STUFF Green Party co-leaders Metiria Turei and James Shaw. Their policy on water is expected this weekend.

National was also in the minority of parties to all but rule out putting a price on water.

The blue-green approach has opened up space on both its right and its left, spaces which were quickly filled.

'FARMERS ARE LIONS, LED BY DONKEYS'

On environmental issues, NZ First has flanked National; not from the left, but from the right.

Its environment policy, as detailed on its website, appears moderate. It notes the environment's international significance, and the importance of living up to the 100% Pure brand; it describes "serious environmental problems and risks" which "need to be addressed".

How that policy plays out in rhetoric, however, shows a blunter approach, in line with its Trump-esque effort to channel the anger of the regions.

At a recent speech to Federated Farmers, leader Winston Peters was very clear: In 2017, NZ First is the farmer's party.

Throughout his speech, he repeatedly defended farmers from criticism, and questioned the Government's commitment to the industry.

He said Guy was wrong to say there were limits on farming, and openly wondered why cows were deemed responsible for pollution when urban waterways were also polluted.

"The Kermits", he said [meaning the Greens and possibly the media], "may have declared intensive farming enemy number one, but not NZ First". Farmers rights were being eroded, slowly, like frogs in boiling water.

He pointed out that several NZ First candidates were farmers, and he himself represented a rural electorate.

In terms of policy, Peters said the solution to better water quality was through better technology and water quality reporting. It meant upgrading nutrient tools such as Overseer [a farm modelling system] before they're included in regional plans.

Any attempt to price water, which would likely have to include an acknowledgment that Maori have a particular interest in freshwater, would be firmly rejected.

The focus of his speech was emotive, and ended with a plea to farmers, who traditionally vote National: "Farmers are lions, but frankly, they are being led by some right royal donkeys."

TO THE LEFT

With the Government on the backfoot, forced to defend its environmental record to an increasingly skeptical public, it presented an opportunity for the left.

It has been another fine line to draw, however, particularly regarding the extent to which they're willing to go after the sacred cow.

Both Labour and the Greens are broadly in alignment on water issues, based on what they've announced so far.

So far, neither has taken the step of committing to reducing cow numbers, a step favoured by advocacy groups.

The Green Party – yet to announce a full policy, with announcements likely at its annual general meeting this weekend – has thus far targeted water bottlers and protecting drinking water, in the wake of Havelock North.

About 45,000 people each year drink water contaminated with E.coli, according to Government figures – its policy commits to upgrading water supplies to protect human health.

Labour, thus far, has been more explicit about targeting the farming industry.

Its key policy would require any intensification, such as more irrigation, fertiliser, or livestock, be subject to a resource consent process.

It would also refine the NPS-FW to include standards for pathogens, nutrients and ecosystem health, not just E.coli.

It would likely require changes to farming practice in some areas if the standards were strict enough.

Both parties are committed to some form of royalty on commercial water usage, including irrigators. How that would look remains to be seen, and an announcement from Labour is expected next month.

And both were willing to address the issue of Maori interests in freshwater, worms which have thus far remained canned due to the Government's refusal to price the resource.

A joining of the two parties is easy – they both favour regulatory measures, and cross over on the major issue of pricing water. How prospective bedfellow NZ First fits into that equation remains a thornier problem.

POLLUTER PAYS

While the other parties jostle for space on the left and right of the Government, the newest entrant appears to have come from underneath them entirely.

The Gareth Morgan-led The Opportunities Party (TOP) is starkly opposite to NZ First in most ways, but the two parties share one thing: on their websites, both use an image of Aoraki/Mt Cook to illustrate their environmental policy.

For NZ First, its an iconic, sweeping vista of the winding road headed for the mountain, drenched in sunlight; for TOP, its a fuzzier picture, with cattle grazing in the foreground, the mountain rising above.

It speaks to their positions on the issue: NZ First is the party of farmers, but TOP has not shied away from the sacred cow.

It has proposed a "polluter pays" system to address water quality, using market mechanisms, not regulation, to improve water quality.

In effect, it would target the bottom line of those who pollute, even if it puts them out of business.

The ethos is that environmental damage should be a cost of doing business, a cost not currently accounted for.

In practice, it would mean water quality limits – set by default at "swimmable", unless communities choose otherwise – set in individual areas.

Those who pollute more than their fair share would pay a fine; those who pollute less would receive money from the penalty pool.

TOP also advocates for greater use of environmental taxes, which it said were low in New Zealand. It would introduce a moratorium on land intensification until catchment-level water quality plans were in place.

Like the left parties, it would impose a resource rental on commercial water usage, adjustable based on the quality and abundance of the water, with revenue going towards environment investment.

That would include resolving Treaty claims over freshwater.

It shares more overlap with the left parties than the right, but speaks to National's belief that the environment and economy must improve together – a third way to the entire debate.

Whether freshwater plays a part in what happens in the days after September 23, or falls aside amidst other inter-party squabbles, remains to be seen.

But for the first time in a long time, parties are being forced to defend their positions on freshwater - and voters have showed a willingness to punish or reward them for it.