In time other catchments will get the same flyover treatment. The Rangitīkei is first because it is the most pristine river in the region, and because intensive winter grazing is known to take place there.
Flying was an expensive way to monitor the practice, Bevin said, but it covered a lot more ground than people driving around in vehicles.
The flights will be followed by site visits during which staff will talk to landowners about good and bad practices, and take action against practices that are unacceptable. Action could range across a spectrum, from abatement notices to prosecution.
The council has previously used planes to monitor vegetation clearance and forestry practices. In 2019, it resulted in charges against forestry company John Turkington Ltd - some are still before the court.
For Carlyon the flyover monitoring is great news. He's a former Horizons staff member and now the director of environmental consultancy The Catalyst Group.
It funded its own aerial survey of intensive grazing practices in the Rangitīkei four or five years ago.
"We found an enormous amount of both feedlotting and winter grazing on the margins of the Rangitīkei River," he said.
That finding caused consternation, and "probably" led to the formation of the Rangitīkei catchment group.
He's under the impression things are much better now, because practices have improved in the past few years.
Horizons introduced rules on intensive winter grazing in 2011, but it hadn't monitored the practices or enforced the rules, Carlyon said.
"If you don't go looking, then practices drop off."
It would be helpful if Horizons let the public know what it found in the flyovers, and if it talked about how that was assessed, Carlyon said.
The Government was delaying new requirements for intensive winter grazing until May 1 next year, Bevin said, but it still required the practice not to expand and it expected measurable improvements within 12 months.
People seeing unacceptable practices, such as cattle in waterways, can ring Horizons' pollution hotline, 0508 800 800.