Water recovered through both on-farm and off-farm measures has returned just 2.1 gigalitres so far at a cost of $68.1 million, the study by The Australia Institute and Conservation SA says, equating to just 0.46 per cent of the 450 gigalitres promised.

The report, titled 1200 Bridges Too Far, also found that money allocated for the scheme may now be used to upgrade over 1200 bridges and increase water storage capacity in New South Wales irrigation districts.

But it says 31 of the 34 projects proposed would have little or no prospect of genuine water recovery.

“Using money that was intended to increase the amount of environmental water in the Murray to build unrelated infrastructure upstream would be a bridge too far,” report author Kate McBride and The Australia Institute fellow Anne Kantor said.

“Transparency, accountability and the efficient use of resources must be at the heart of decision making within the Murray Darling Basin, but the lack of clarity surrounding this program is concerning.”

The Australia Institute and Conservation SA have recommended a full audit and reconsideration of the program before any projects are approved.

Conservation SA Chief Executive Craig Wilkins said the commitment to deliver an additional 450 gigalitres of water downstream was a deciding factor in South Australia agreeing to the basin plan.

He said water ministers in the basin states must commit to buying back water if the recovery target is not met by the 2024 deadline.