The group was "farmers educating farmers, working towards a common goal" and was considered the model to follow in New Zealand.
"It's been a trailblazer."
From various government funding, the group launched the project, aiming to install 100km of riparian fencing and more than 220,000 riparian plants.
The project had gone "pretty well" so far as "we are all in it together".
So far, 89,000 riparian plants had been put in the ground.
By the end of this month, he expected the figure to hit 100,000 plants "which is awesome."
About 56km of riparian fencing had been installed and another 15km of fencing had been ordered.
The improvements had been made across 65 farms and another dozen farms were "ready to go."
Discussion had started to include another 28 farms in the project, he said.
Once those farmers had joined, about 95 per cent of the plants and fencing would be allocated.
The plan was to "over-allocate" the project and continue working "until the money runs out".
When the project was over, riparian planting and fencing would be on about 110 farms, for future generations to enjoy.
"We've got the pleasure of planting them and our great-grandchildren are going to have the pleasure of climbing them."
Group chairman Simon O'Meara, of Moa Flat, praised the farmers at the celebration who had spent their time and money on riparian fencing and planting, managing nutrient loss and winter crops to improve the water quality of the river.
"A big thank you to them."
Testing showed the water quality of the river was improving and everyone involved should feel a "sense of achievement".
Te Tai Tonga MP Rino Tirikatene said he was "delighted" to be part of the celebration.
He acknowledged the group, farmers, government and community which were behind the "important kaupapa" of the project.
Kaupapa are principles and ideas which act as a base or foundation for action.
"This will go on for generations - we are laying the groundwork for tamariki and mokopuna to come."
The work would ensure the land would remain productive, biodiversity would flourish and the quality of the "beautiful awa [river]" would improve.
To recognise the project stakeholders, several native plants were put in the ground at the celebration.