About 1000 people marched in Christchurch on Friday to protest against plans for an irrigation scheme in North Canterbury.
The Hurunui Water Project aims to irrigate up to 42,000 hectares of farmland near the Hurunui River.
The scheme has outraged some river users, who say the 75-metre-high dam planned in the south branch of the Hurunui will inundate about 525 hectares.
Environmentalists say the project will effectively privatise a public resource, while the Hurunui Dambusters group says the scheme will destroy 7km of pristine river.
Demonstrators waving placards marched through central Christchurch shortly after midday, while kayakers on the Avon River also mounted a protest.
Amanda Loeffen, of the Hurunui Water Project, says they are willing to try for a scheme that benefits farmers without harming the environment.
She says the resource consents have been put on hold for a year to allow for more consultation, but the protest action on Friday flies in the face of attempts to work collaboratively.
However, opponents say they are determined to keep fighting the proposal.