Award-winning sensor will give farmers power to save rivers

A Wairarapa farmer says it's farmers, not politicians, who control the fate of New Zealand's rivers.

The degradation of a river running through his land pushed Grant Muir to help develop the River Watch sensor to give communities the ability to test their own waterways.

The Pahaoa River in remote Wairarapa is usually muddy from livestock damaging its banks, and "foambergs" swirl in the eddies as a result of phosphate run-off.

Fifteen years ago, Mr Muir remembers keeping a fishing rod at the back door of his farm cottage to catch the abundant trout.

Not anymore.

"I saw it deteriorate from a river that was teeming with fish, to having absolutely no fish over about a three to four year period," he says.

That spurred him into action, deciding communities need technology to gather data on their waterways. He teamed up with Victoria University to develop the River Watch sensor.

It's a device that's left in the river and collects data every ten minutes on dissolved oxygen, pH, turbidity, temperature and conductivity, with a sensor for nitrates soon to be added.

Solar panels mean it can be left for days, and WiFi sends the data straight to a computer or smartphone app.

Mr Muir says the sensor can be used alongside the macroinvertebrate test to give a well-rounded picture of river health.

"You'll see changes in water in the daylight to evening hours, different types of weather events and actually be able to build up a wireframe of data rather than just taking a snapshot."

The Pahaoa River starts in hill country and from Mr Muir's farm it flows 18km out to sea. It doesn't run through any towns or dairy farms, but it still has problems.

It runs through land where beef farming has been intensified, adding to erosion problems.

Mr Muir says his criticism of neighbouring farmers grazing their stock on the riverbanks caused tension.

"People saw it as a threat when all of a sudden you're saying, 'Well no, I don't agree with your farming practices', and they found it very hard to change because some of them have been doing this for 50 years."

He says decision-makers can legislate all they want, but nothing will change unless farmers get onboard.

"The change has got to come from within, it's got to come from the people who live in those places."

Currently a similar water tester would retail for $25,000. Mr Muir hopes the River Watch sensor will retail for about $2000 to make it affordable for communities.

The device won the 2016 WWF Conservation Innovation Award and some of the prize money has gone towards commercialisation.

Mr Muir hopes to have it on the market by October this year.