USING the Murray Darling Basin Authority's own flow data, Southern Riverina Irrigators has filed a class action in the NSW Supreme Court claiming $750 million damages for the past season in which its members received no irrigation allocations.
SRI represents 1200 farm businesses producing food and fibre across a 748,000 hectare footprint.
SRI chairman Chris Brooks said the MDBA has been running the Murray River at "hideous levels", losing 6200 megalitres a day for 141 days straight in spring and summer to over-bank flows.
He said by running the river over capacity, the MDBA was responsible for losses exceeding 870,000ML of water, which could have instead been used by farmers to make money.
Murray Irrigation Ltd, which delivers water to SRI, has an entire allocation for irrigators of 8.3GL, or 830,000ML.
Murray Irrigation's chairman Phil Snowden refused to comment on the SRI claims, suggesting the MDBA or Department of Industry-Water would be better placed .
However, Mr Snowden in February he conceded he feared there had been "extraordinary and excessive" losses, depriving customers of as much as 200GL to 400GL of water.
"Despite being Australia's largest farmer-owned water delivery company, Murray Irrigation's largest single customer operation is the delivery of environmental water," he said.
"Our criticism is not of the Basin Plan, but the decisions being made to run the system that delivers it."
He said that on the eve of Murray Irrigation releasing a 5 per cent irrigation allocation to clients for free - or 53GL - drawn from the body's operational efficiencies, the same day of another announcement of zero irrigation allowance.
Mr Brooks on said SRI members felt they had been backed into a corner "and now we're coming out swinging."
"They (the MDBA) have been running the river that hard, the Barmah Choke, which was once a restriction that could carry 8000ML a day can now only carry 7800ML, because the banks are collapsing and the river has silted up," he said.
"If the water wasn't in the system then we would not be taking this course of action.
"But the water was there, but was lost due to what we believe was mismanagement." He said the losses were unnacceptable and that was why farmers carrying the costs of those losses had initiated court action.
"This mismanagement has cost people their stock, their farms, their jobs and even people's lives.
"Someone has to be held to account, our politicians are not holding water managers to account, so what other option do we have?"