Farmers, traditional owners, scientists, and politicians have told the two-day Listening To The Lachlan conference about the impact expanding dam will have on the Lachlan River.
Cowra beef and cropping farmer Kerri Webster said some of her most productive farmland will be compulsorily acquired if a proposal for the dam's expansion goes ahead, and that her family had not been consulted.
She told the conference in Forbes the dam project has the potential to cause significant losses in agricultural productivity in the Upper Lachlan.
"The environmental impact of this project will be disastrous and irreversible in our area, with hundreds of river red gums in the inundation zone that are hundreds of years old that will be waterlogged."
"We get frustrated, angry, we're very emotional ... we're completely perplexed," she told the conference on Tuesday.
Beef and lamb producer Louise Crawford, who lives nearby, also warned of the consequences.
"(It) will turn our headache into an absolute migraine," she told the conference.
The NSW farmer said the project would mean trees will die, and access to her land will be restricted.
"I believe enlarging Wyangala dam is robbing Peter to pay Paul ... it's just plain unfair."
Sheep farmer Hugh McLean from the Lower Lachlan flood plain group also wants to stop the expansion project and worries the economic impact of others further downstream haven't been considered.
The farmer from NSW's Riverina said each time the dam spills it doubles the income his farm generates, which works out as a $7,500,000 boost to his region over two years plus 19 full time jobs.
"When the floodplain goes under water that production is doubled over a two year period," he told AAP.
The chief executive of the Lachlan Valley water group - which has advocated for the dam wall to be increased for flood mitigation and water storage - also spoke at the conference.
Mary Ewing told the conference that crop losses from the 2016 floods were estimated at $500,000,000 and any business case needs to be thorough.
"We know the business case must be done, the environmental impact assessment must be done," she said.
Chair of the Lachlan valley water group Forbes farmer Tom Green told AAP that early studies had shown that raising the wall would benefit the local communities.
"We need to see the modelling ... we believe the project has shown it will be highly effective for both flood management and water security," he said.
Mayors along the Lachlan including Forbes, Cowra and Lachlan shires remain committed to raising the wall.
Forbes mayor Phyllis Miller told AAP it needs to go ahead.
"To those people that raising the wall and inundating some land up in the dam catchment is an environmental problem, let them come see what a flood does," she said.
The NSW government also remains committed to the raising of the dam wall.
Water minister Kevin Anderson told AAP the government and the former federal government agreed to co-fund the Wyangala dam wall-raising, and the money is contingent on a co-funding agreement.
"I look forward to continuing discussions with the new federal government and receiving a commitment to funding these crucial water infrastructure projects," he said.
"Water security is critical to the survival and the future of regional communities."
The NSW government said it would not be releasing the final business case as it contains information that is commercial in confidence and cabinet in confidence.
An environmental impact statement is expected to go on display after August.
Federal water minister Tanya Plibersek was unavailable for comment.
24°C