A freshwater ecologist says farmers in New Zealand are working on a "broken model" and it is having an adverse effect on water quality.

Dr Mike Joy told Duncan Garner on the AM Show this morning farming practices need to be changed to prevent the situation worsening.

He said: "I don't blame the farmers, I mean they're just doing what they have to do. It's the lack of leadership and the system that we have that's so dependent on fossil fuel derived fertiliser and palm kernel that has cranked system up way ahead of where it was two or three decades ago."

Dr Joy said the rise of farming on lands that were unsuitable for intense dairying was also a cause of poor quality water.

Citing the Canterbury Plains Dr Joy said: "These are sort of gravelly outwash lands from the mountains, there is very, very porous soils. You put cows on there and what comes out goes straight down into groundwater, into our rivers, into our aquifers."

He also discussed a recent warning in Ashburton where mothers were told to use bottled water to feed their babies, after it was found that tap water was causing the babies' lips to go blue.

Mr Joy said this was the "first of many signs that we've gone way way too far".

Newshub.