The health of New Zealand's rivers and lakes is undeniably a controversial and divisive subject.
Kiwis feel passionate about the health of their waterways, and rightly so, but sometimes the real facts behind what is polluting them can be buried behind hyperbole and over-zealous views.
This was on display in abundance when Environment Minister Nick Smith announced his '90 percent Swimmable Rivers by 2040' decree last week.
Dr Smith laughed off criticism of the plan, which is essentially to fence off all Kiwi waterways from livestock by 2030 and change the criteria of what swimmable water actually is, as 'junk science'.
In a special report into the state of NZ's waterways, Newshub has interviewed and gathered resources from several independent freshwater scientists, the dairy farming industry, (including farmers and scientists) and NIWA, to give you the full picture on the health of New Zealand's rivers.
Part one of Newshub's special investigation will focus on what exactly is the pollution being put into our rivers and the effects.
Part two will analyse the efforts being undertaken to protect Kiwi waterways from further pollution, and what is being done to reinvigorate those rivers that are failing.
Part three will examine the effects of climate change, and whether or not we've reached a tipping point for overall river health decline in New Zealand.
Part four will look at the battle over the blame of our failing river health, and conclude just who is responsible for the overall decline in freshwater quality.
Part One - What is polluting our rivers?
It's hard to argue that many of our low-lying rivers are being polluted and that the agriculture industry, and in particular beef and dairy farming must take a fair share of the blame.
To its credit, DairyNZ says it has spent over a billion dollars in combating river pollution, and implemented science-based regulations that leading water experts say have helped turn the tide in improving the health of many our waterways.
And while it's easy to simply point the finger at dairy farming, all agricultural industries, and indeed all New Zealanders, even city dwellers, must carry some of the blame for our water pollution.
What is the main cause of this pollution?
That question at least has an easy answer: Agriculture - but it's not been a recent occurrence, it's been happening since the first pastoral farms were created in New Zealand in the 1800s.
But with the agriculture industry being a big player in the New Zealand economy, examining the link between pollution and agriculture can be tough to evenly gauge.
What are the main contaminants?
Sediment: Fine material from deforestation
Nutrients: Nitrogen and phosphorus from livestock urine and fertilizer
Bacteria: E. Coli from livestock excrement
Sediment from deforestation
It's easy to forget New Zealand is one of the most deforested nations on Earth, with only 25 percent of our native forests left untouched, and they're mostly on the west coast of the South Island.
So while New Zealand does have pockets of beautiful and unspoiled native forests, the majority of our land has been cleared and is used in the agriculture, and in particular, the farming industries.
We've also cleared 95 percent of our native wetlands, which if they were still in existence, would play a major part in protecting waterways from pollution.
New Zealand's native forests have been burnt off and cleared ever since human settlement began 800 years ago, and our waterways are now paying the price.
Dr John Quinn is NIWA's chief scientist of freshwater and estuaries, and told Newshub this initial clearing of New Zealand's forests has a continuing impact on our waterways.
"There would have been a huge dollop of sediment happen when land was first cleared, and often that was just done with burning and pretty unfriendly sorts of approaches and there are legacy effects of all that deforestation that are still around our river channels today.
"Some input of sediment in rivers is part of a natural process, it creates sandy beaches. You have to have a level of erosion that is part of the natural system; it's just how much has it been accelerated."
Dr Mike Joy teaches environmental sustainability at Massey University. He's studied the declining health of New Zealand rivers for decades and has long been a vocal figure in raising awareness.
"When we get heavy rainfall events we get huge amounts of fine material from deforested areas.
"This sediment comes off the land and clogs up the rivers making them brown and dirty, but the biggest impact is that the sediment then forms a mat over the bed of the stream, and cuts off all the habitat for the life in it."
Dr Tom Stephens works as a water scientist for DairyNZ and his chief job is to help farmers try and improve their water quality. He says one of the industry's biggest battles is to protect our rivers from further sediment gain.
"Once it starts to move on the land it takes a long time to slow down. If it gets in our waterways it takes a long time to get out, so we're talking decades to century's worth of sediment loss. It's what we're currently trying to address through our water quality levels."
Dairy farming is only part of the sediment problem
Dr Quinn says high intensive dairy farming is 'a' cause, but drystock farming (farming animals for meat and wool) is much more widespread - and has been since the 1800s.
"If you look at the amounts of sediment that comes off that drystock farming, and partly because it's on the steeper hill country, it's more erodible as well.
"So dairy's part of the problem but is certainly isn't all of the problem."
Nutrients from farm animals
This is where the booming dairy and beef industries must take a fair share of the blame for the high levels of nitrogen being put into New Zealand's waterways - the direct effect of high volumes of cow urine.
Dr Joy says nitrogen produced by cow urine is having a major detrimental effect on New Zealand's waterways.
"If anyone's seen a cow peeing it's a huge volume in a small area, and the land and the plants can't possibly cope with most of it and it makes its way through the soil.
"Depending on soil moisture, levels of rainfall and a whole lot of other factors, most of it makes its way through the ground to lakes to rivers.
"It's not so much the nitrogen itself that's the problem, but that it's a nutrient, and it grows in the plants and the lakes, and there's algae and then algal bloom; either toxic algae, or algae that grows to such an extent that it takes the oxygen out of the river, out of the water itself and the animals die."
The dairy industry is of course incredibly aware of the nitrogen problem from cow urine, and is trying to use the latest science to combat it.
"The biggest challenge for us is actually catching, and interrupting that urine patch," says DairyNZ water scientist Dr Tom Stephens.
"When it's deposited it's in a very dense, sudden pool, and it can escape the surface layers of the sediment where the root systems are and where the growth is occurring and where that nitrogen would otherwise be captured, and once it escapes that then it's going to travel.
"It will either go into the ground water, and it will take years and decades to then emerge or, and a lot of the nitrogen on a dairy farm will do this."
Human health issues from bacteria and in particular: E. Coli
E. Coli comes from the faeces of animal livestock, and has become a major factor in stopping Kiwis from swimming in their rivers. E. Coli is a major health hazard - it can make you sick, especially if you drink water contaminated with it such as what occurred in Hawke's Bay in 2016.
DairyNZ regulations mean its farmers must fence off all waterways on their land and 96 percent have done so - but no such regulations exist for beef, sheep or deer farming.
Environment Minister Nick Smith wants this compulsory across all farming industries by 2030. One wonders why it has taken the Government so long to implement such a measure.
It's not just agriculture and farming polluting New Zealand's rivers
The Tasman Pulp and Paper Mill is continuously polluting the Tarawera River in the Bay of Plenty, and is being allowed to do so because the mill hires local people. The Tarawera River now has an unenviable nickname, the 'Black Drain'.
This perhaps sums up the great dichotomy of employment versus the environment: Our Kiwi communities want jobs, but they also don't want to pollute our rivers.
In 2009 the Government granted permission to the mill's owners, Norwegian company Norske Skog, to keep polluting the Tarawera River for another 25 years, despite official protests from local iwi.
In essence, the Tarawera river is being destroyed to keep a few hundred local people employed. The profits made by the mill go back to 'clean, green' Norway.
Invading species is also a massive problem
Remember those "have you seen didymo" TV ads a decade or so ago?
Invasive plants and animals in our waterways are still a major problem in 2017, with foreign species of fish like Koi Carp wreaking havoc on the natural vegetation in our Kiwi lakes, exacerbating the decline in water quality.
Dr Quinn says noxious plants like didymo are still common in New Zealand but have been overshadowed by the pollution saga from agriculture.
"We see a whole lot of nuisance plants getting into our lakes which eventually results in quite major deterioration.
"It's quite difficult at times to get simple messages across to the public because it really is quite complicated and often people want to reduce it down to one or two things and what we're dealing with is a syndrome of impacts that humans are having and we really need to understand is how to manipulate a number of things at once if we're to restore these water bodies to what we want them to be."
Tomorrow, in part two of our special Newshub investigation into river health, we'll examine what exactly is being done to help protect New Zealand waterways and hear extensively from dairy industry scientists and perhaps the most important people in all of this - the farmers.
By Tony Wright and Newshub.