Once a stark illustration of wetland destruction, a giant floodplain in the Riverina district of New South Wales could soon be a shining example of environmental restoration.

Key points: NSW Government announces partnership for ambitious restoration project

NSW Government announces partnership for ambitious restoration project Area involves 11 farms purchased in largest water buyback of Murray-Darling Basin plan

Area involves 11 farms purchased in largest water buyback of Murray-Darling Basin plan Conservation, Aboriginal and scientific groups to work together

The ABC can reveal the NSW Government has chosen the global environmental charity The Nature Conservancy, in partnership with Aboriginal and scientific groups, to be the managers of the Nimmie-Caira project — arguably the most ambitious environmental project to come out of the Murray-Darling Basin Plan.

"When the European explorers arrived in Nimmie-Caira something like 150 years ago, they thought they had found the inland sea," The Nature Conservancy Australia director Rich Gilmore said.

"All they had found was the Murrumbidgee in flood. What we want to do is reinstate that natural flooding to bring back that inland sea that the explorers thought was so incredible."

On Tuesday, Mr Gilmore, the NSW Minister for Regional Water Niall Blair and Ian Woods from the Nari Nari Tribal Council marked the partnership with a signing ceremony.

In 2013, the Federal Government spent $180 million buying 11 farms along the Murrumbidgee River, along with their 137 gigalitres of water rights — enough to fill a quarter of Sydney Harbour.

The purchase amounted to the largest water buyback under the $13 billion Murray-Darling Basin Plan.

Those 11 farms were in the middle of a massive wetland area which, despite its ecological importance, had seen broadscale destruction through the 1990s.

Dams, levee banks and water channels had been cut through the landscape, leaving more than three-quarters of the wetlands destroyed or degraded.

In 2004, scientists estimated a fifth of the plant and animal species that lived in the wetlands had disappeared, while waterbird numbers had collapsed, reduced by more than 90 per cent.

In the years since the buyback was announced, doubts grew about the sincerity of the restoration plans, with concerns irrigated cotton would be allowed back onto the property.

Others worried economic activity would be completely excluded, while Indigenous groups feared they would not be adequately involved.

But today's announcement is expected to allay many of those concerns.

"This is a real example of the Murray-Darling Basin Plan being implemented," Federal Agriculture Minister David Littleproud said.

"We're going to see 85,000 hectares of a floodplain come back to natural life, where Indigenous communities can see what it was 50,000 years ago when they first walked that floodplain."

A smoking ceremony is performed to mark a partnership between the Nari Nari people and conservation and scientific groups in the Riverina. ( ABC News: Michael Slezak )

Profits to go back into restoration work

But far from devoting the entire 85,000-hectare site to environmental restoration, the project also includes plans for low-impact grazing, ecotourism and carbon farming.

And that mixed use is crucial to what the NSW Government, which has run the project since 2013, said was the intention of the project.

"I'm so proud of this. In public life you get very few opportunities to say we did something special that will change lives, and this is it," Mr Blair said.

"This is unique. We challenged everyone to think outside the box.

"This gets the balance right. Farming, Aboriginal heritage and the economy are all winners out of this project."

The Nature Conservancy said profits from those activities would go back into restoring environmental work on the property.

The Nari Nari Tribal Council, one of the partners in the consortium, will be managing the property, along with its rich cultural heritage.

The site is home to ancient burial grounds and has evidence of tens of thousands of years of Indigenous occupation.

Mr Woods said the outcome was "fantastic".

"We're so emotional because the process has taken so long. But it had to do that to get the right result. To get our people back on country, and restore country, and get people living on country again," he said.

NSW Minister for Regional Water Niall Blair, The Nature Conservancy director Rich Gilmore and Ian Woods from the Nari Nari Tribal Council participate in a signing ceremony. ( ABC News: Michael Slezak )

Although about half the property was previously used for cropping and grazing, more than half of it has significant native vegetation that is recovering.

Large parts of the property will have their wetlands restored and researchers will monitor how the environment responds.

Two other partners in the winning consortium were the Murray-Darling Wetlands Working Group and the Centre for Ecosystem Science at the University of NSW.

"Nimmie-Caira is a magnificent ecosystem, with outstanding biodiversity," Professor Richard Kingsford, who produced the key research highlighting the significance of the wetland, said.

He said the project would not only be useful for the local region, but would provide data that could help land and water managers better use environmental water elsewhere.

"We can potentially manipulate large volumes of environmental flow and study how native fish respond, the impact on waterbird breeding and on the re-establishment of flood-dependent vegetation," Professor Kingsford said.