Reducing the environmental impact of industrial farming would have a wealth of other benefits on top of freshwater quality, without harming most farmers' profits, environmental scientist Mike Joy says.
Joy is the editor of a new book, From Mountains to Sea: Solving New Zealand's Freshwater Crisis looking at the problem of freshwater, which he says is grave.
"The freshwater crisis is our industrialisation of the landscape and it's ended up with these two worlds," he says.
"We have this amazing conservation estate with the most beautiful pristine rivers and lakes in the world and a lowlands where we have some of the most degraded and polluted lakes and rivers in the world."
He says this tendency to "silo" means we lose track of the bigger picture.
"We've got real lack of leadership. I find we could reduce the number of cows we have in the country - say, a 20 percent reduction - and we would get in most places a 40 percent reduction in the amount of nitrate pollution that comes from that.
"The farmers in most cases would make as much if not more money by reducing, but of course the ones that wouldn't make more money under that model are the big industry players: the fertiliser companies, the Fonterras - and so they go to a lot of trouble not to have reality come out.
"That is part of the problem, this overarching power that is held by industry, and they dominate the research and they have a lot of lobbying power with government.
"Trying to drag the truth out from underneath all that is quite hard sometimes."
The future, he says, lies in diversity not mono cultures.
"There will be permaculture and there will be - instead of mono cultures of cows and mono cultures of crops - real mixtures with tourism mixed in with it.
"The market is growing much faster for non-animal products than they are for animal products. We need to get the jump on that."
Irrigation in the Canterbury Plains is an example of an apparently good idea going very wrong, Joy says.
"Those plains in Canterbury are light, stony soils that are big gravel outwash from the Southern Alps. So when you take water out of the ground or out of the rivers and you irrigate, it very quickly moves through and takes the nutrients and the pathogens through with it into ground water.
"Now, there are many parts of Canterbury where the shallow aquifers are getting close to - or have passed - human health limits and are definitely long past ecosystem health levels and it's happened in a relatively recent time.
"What may seem like a good idea to irrigate actually turns out to be an ecological nightmare."
Economics feed into the problem too, he says.
"Irrigation is expensive, the water is expensive, you drive farmers to intensify to pay for that water and therefore you get more pollution happening, rather than less."
Campaigns to promote the restorative work being done by big dairy do not wash with him.
"There's been no net gain; sure you can do nice things and talk about the right things and support riparian plantings or wetlands in certain areas, but if at the same time you are demanding more product and you are increasing intensity then the net effect is that you've had a 2 percent improvement with your little fiddling and a 10 percent loss with your expansion over a decade and so.
"I see the dairy companies and Fonterra with more and more money being spent on public relations, TV, all sorts of schemes to make it sound like they're doing the right thing."
That money would be better spent on "doing the sums on reducing cow numbers and how farmers could make more profits," he says.
"Moving away from intensity and into adding value and adding diversity will give us all a much better future than this kind of industrial factory model that we're trapped in at the moment."