The Murray-Darling Basin Authority omitted evidence from a report on satellite monitoring technology that apparently showed water bought by taxpayers for environment purposes was being sucked up by a downstream irrigator, a former senior staffer said.

The discovery of the diversion of water in the first half of 2016 was "by accident", as the authority was testing Data Cube remote sensing developed by Geoscience Australia, said Maryanne Slattery, a former director of environmental water policy at the authority.

The release involved about 9 billion litres let out by the Commonwealth Environmental Water Holder, with the area of interest from the satellite imagery centred between Boorooma, where the Macquarie River flows into the Barwon, and the town of Brewarrina.