The Green Party, farmers and Forest and Bird are backing a report which says bottom lines must be set for water quality.

The government is cautious and says it will study the report.

The Land and Water Forum released the report on Friday, saying iwi, urban and rural communities should work together to develop water quality objectives.

"This means, for the first time, establishing some national bottom lines for the state of our rivers, lakes, streams, wetlands and aquifers," the forum said.

The Greens say the government must implement its recommendations.

"More than half of our monitored rivers are unsafe for swimming, one third of our lakes are unhealthy and two thirds of our native freshwater fish are at risk or threatened with extinction," water spokeswoman Eugenie Sage said.

"The report is clear - something has to give."

Federated Farmers, a forum member, says the bottom lines must be equally applied to rural and urban waterways.

"We don't think it will be easy or painless - there's a vital economic dimension communities will need to grapple with and this will create tension," federation president Bruce Wills said.

Forest and Bird says the report lays down a clear plan for reversing the "relentless decline" in water quality".

"This is a really significant breakthrough," spokesman Kevin Hackwell said.

"Forest and Bird is really pleased the forum's 60 stakeholders and five iwi members reached a consensus ... this means we will be able to put more money and resources into managing water resources rather than into expensive and wasteful court battles."

Environment Minister Amy Adams says she's impressed with the way the forum's diverse members worked together.

"There is plenty to consider in this report, including how the recommendations could be progressed within the wider work the government is doing to reform the Resource management system," she said.