Every few years, Wyangala Dam overflows, and the runaway water escapes down rivers across NSW.

In the lower Lachlan floodplain, just north of Hay, this creates massive flooding events, which attract hundreds of thousands of Straw-necked Ibis and other migratory birds, sparking a large-scale breeding event.

Local farmer Gordon Turner said witnessing the phenomenon in the Booligal Wetlands was an incredible experience.

"These once or twice a decade events are really quite awe-inspiring," he said. "To see how the country can just suddenly change. And when we get those floods, the water birds get into breeding mode, so it's pretty amazing to see that when it happens."

The NSW Government has recognised the area as one of the most important bird-breeding sites in the country.

But there are currently fast-tracked proposals to raise the Wyangala Dam wall by 10 metres, in order to add 650 gigalitres of storage capacity to the reservoir, despite reports suggesting this extra water will rarely be used.

IN OTHER NEWS:

Mr Turner has over 20 years experience in water management groups, and said raising the dam wall would likely bring an end to the flooding events which are so crucial to the wetlands' ecosystem.

"We need those once or twice a decade floods to provide the water depth, the lateral spread and the duration," he said. "Without that, the events won't happen and the birds won't come ... we can see the risk of this project."

Mal Carnegie is the project manager of Lake Cowal, north of West Wyalong, which relies heavily on the overflows from Wyangala Dam.

He questioned the lack of a due process since the project was announced, and said there had been no consultation of communities down stream of Wyangala which would be heavily impacted.

A number of concerns over the project have also been raised by various groups, including Indigenous communities, who said it will result in the destruction of various sacred sites.

While construction is taking place to raise the dam wall, the reservoir can only be at 30% capacity, which has raised concerns over water security for irrigators.

The Guardian is also reporting that the potential cost of the project has blown from an initial $650 million to more than $1.5 billion, before it has even received approval.

The State Government is currently investigating the financial and economic impact of the proposed project, and both Mr Turner and Mr Carnegie are urging those in power to speak with local communities to gain their insight.

"My family has been in the Booligal district for more than 140 years," Mr Turner said. "So we've got generations of knowledge, and a lot of interest in the local environment."

In 2016, the Department of Agriculture Water and the Environment uploaded a video to YouTube showcasing the rare breeding event: