Concerns about the Warrego buyback also extend to how it avoided water cutbacks in the Borders Rivers, a more prosperous region spanning southern Queensland and northern NSW dominated by major irrigators. Maryanne Slattery, a senior analyst with The Australia Institute who examined the documents, said Mr Joyce's support for the purchase of 10.611 billion litres of annual water rights from Tulla starkly contrasted to his opposition to a buyback in the Warrego River by the Rudd government in 2008. The environmental water would probably "merrily" go down the Warrego and "quickly dissipate" before reaching the Barwon-Darling and the rest of the river system, then Senator Joyce told Parliament at the time. "It is a sad day indeed when this sort of process is peddled out there." Loading Fairfax Media sought comment from Mr Joyce and his successor as water minister David Littleproud.

"The government has been fully transparent with water purchases," a spokesman for the agriculture department said. "The Warrego purchase was consistent with Commonwealth Procurement Rules and paid at a fair market rate, as informed by independent market valuation." Tulla's owner Geoff Dunsdon stated in a letter to the department in January 2017 that water valuations were "difficult given the lack of a trading market or historical water sales". The price of a separate sale of his property's water as part of the Healthy Headwaters Program was redacted. Mr Dunsdon declined to comment on the prices - including what he paid for the original licence in 1999 - telling Fairfax Media it was "private business". Ed Fessey, who served on the North Basin Advisory Commitee for the Murray-Darling Basin Authority, said the water sold by Mr Dundon only existed in one-off flood events, and is known locally as "goanna water". "The only time you get it is when goannas are sticking their heads out of the trees [because of flooding]," Mr Fessey said.

Even with its intermittency, the Dunsdon deal would potentially deliver a hammer blow to the region, Lindsay Godfrey, mayor of Paroo Shire and part of Mr Littleproud's electorate, told Fairfax Media. "I was quite shocked when it was announced," Cr Godfrey told Fairfax Media. "Nobody thought the Warrego was on the agenda for water buybacks." Loading The mayor was particularly irked by the government's reluctance to reveal how much water had been bought, a figure they only gleaned from tender documents, he said. The sale had the potential to lop $6 million from the shire's annual output of about $95 million, Cr Godrey said, adding he had sought compensation from Mr Littleproud's office.

Ms Slattery, who formerly worked for the Authority, said the Warrego purchase had "serious implications" for the recent amendments to the Basin Plan that failed to pass the Senate thanks to the Labor, Greens and Xenophon senators teaming up to block them. In a report released Sunday by The Australia Institute, Ms Slattery said the proposed amendments allowed the Authority and the states to change diversion limts in a valley "without any consideration of the science". "This [buyback] deal matters because it shows how the people who are in charge of our greatest river system feel free to make decisions regardless of the rules and regardless of the science," Ms Slattery said. "It undermines confidence in the politicians and public servants who claim to act in the best interests of the public and the basin, and then contradict their own stated positions and do deals without public scrutiny." An authority spokeswoman said it "absolutely rejects any accusation that it has misled Parliament or the public". "The public’s confidence in the Authority waned significantly after the water theft events of last year, but now it’s reached the point where there needs to be a purge of senior management personnel such that confidence can be restored," Senator Patrick said.