Deniliquin farmer Louise Burge has lost at least one hundred sheep while thousands more are stranded. She's reliant on food drops by SES helicopters to keep them alive.

"It's absolutely beyond catastrophic," she told AAP.

She said the flooding had been made worse by what she called mismanagement of the Hume Dam at the headwaters of the Murray River, a claim the management authority rejects.

The farmer says landowners had pleaded with the Murray Darling Basin Authority (MDBA) to keep Hume Dam at 87 per cent, and if that had happened the flooding wouldn't have been catastrophic.

"I am still saying we would have got a flood, ... we should not have had such quick releases of such large volumes (of water) out of Hume ... the system was just swamped with water," Ms Burge said.

She blamed the authority and the NSW, Victorian and South Australian and federal governments.

"The MDBA has been warned for 12 years that they have to acknowledge that if they overfill the dams in wet years they will elevate the flooding risks," she said.

"They had been running the Hume Dam at up to 98 per cent this was despite Dartmouth dam ... in Victoria near spilling."

Her family and neighbours have spent the past week moving thousands of sheep to higher ground.

Ms Burge said about one hundred sheep have died and three thousand are still stranded.

Helicopters co-ordinated by the state emergency service spent Thursday dropping hay to the waterlogged properties.

And it's not just livestock the farmers have lost.

"We've lost the majority of our crops, we've lost just about everything," Ms Burge said.

Despite planning for the worst for months, she said nothing could have prepared them for the flood and the situation was made worse when the levee banks broke.

It's the third time the area has flooded in a month, with water levels peaking this week.

"The Edward River was higher than it's ever been before," she said.

The Burge's sheep are trapped on islands and are expected to be stranded for weeks.

All four of their properties southeast of Deniliquin are under water. Thousands of acres of farmland remain submerged.

With most of the crops washed away or eaten by hungry livestock, Ms Burge is worried about what happens to the sheep when the helicopter leaves.

"We can't truck them out and we're going to have to keep helicopter feeding for I don't know how long ... all the feed is ruined," she said.

"We don't know how we're going to feed these sheep because they're going to be stranded for a month or more."

Andrew Reynolds from the Murray Darling Basin Authority said it was up to basin state governments to set the rules for how Hume and Dartmouth dams are managed, and that the authority had been carefully and closely managing the storages.

"Our priority is keeping the Hume and Dartmouth dams safe, capturing and storing water, and where we can, mitigating floods," said the river management executive director.

"We strongly reject claims of mismanagement."

Mr Reynolds said there had already been significant flood mitigation to communities downstream of Hume Dam, and noted there had been unprecedented rainfall and flooding across large parts of the Basin.

"Our river operators monitor weather, inflows and forecasts around the clock and manage Hume Dam releases as conditions change," he told AAP.

The Victorian government said it continued to focus on the emergency flood response.

"Victorian manages its water storages to provide a secure and safe water supply," a government spokesman said.

The federal government referred AAP back to the authority and basin state governments.

Responses were also sought from the NSW and SA governments.

Australian Associated Press