A new documentary about the state of New Zealand's rivers will have its Hawke's Bay premiere this Friday.

Seven Rivers Walking focuses on the rivers of the heavily-farmed Canterbury plains.

Co-director Gaylene Barnes said it was a film she wanted to make for a long time.

"I've been trying to make a film about the dairying on the Canterbury plains for about 10 years."

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Ms Barnes said although urban rivers also had issues with pollution, the heavy use of fertilisers and irrigation was having a major impact on the country's waterways.

"I reckon they're going to be lifeless in 20 or 30 years.

Co-directors Kathleen Gallagher (left) and Gaylene Barnes. Photo/Supplied
Co-directors Kathleen Gallagher (left) and Gaylene Barnes. Photo/Supplied

"We need to shift the mentality of the farming community."

One major issues was the level of nitrates in the water, as it is toxic to fish, she said.

Nitrates from cow urine commonly ended up in nearby rivers, as well as soil.

While she was initially concerned with irrigation draining rural waterways, Ms Barnes said she was now equally troubled by pollution.

"The water quality thing has been a revelation for me in the last year."

She said a lack of water made pollution worse and vice versa.

"We tried to separate them out in the film, but you can't."

The film focused on people concerned with rivers and their stories, co-director Kathleen Gallagher said.

"This documentary is about passionate Kiwis who care deeply about their rivers and environment and want to turn the tide."

The founding director of the New Zealand Film Festival, Bill Gosden, has praised the film.

Waimakariri River - another of Canterbury's braided rivers. Photo/File
Waimakariri River - another of Canterbury's braided rivers. Photo/File

"In the polarised political environment of 2017, this film is a disarmingly peaceable one.

"It places the hope of change in a shared love of our rivers and riparian environments and a profound appreciation of their ecology.

"Anglers, rafters, trampers, Kai Tahu, Fish and Game, Forest and Bird, natural scientists, farming families old and new, all bear witness."

Seven Rivers Walking (Haere Marire) initially premiered in Christchurch last month, with 800 people attending.

The Hawke's Bay premiere is this Friday, September 15, at Focal Point Cinema, with pre-film drinks from 5pm.