A former government water chief says the Queensland government has "no clue" what Adani's mine and others will do to the state's underground water sources.
Tom Crothers is a former general manager for water allocation and planning in the Queensland Department of Environment and Resource Management, and is now a water policy consultant.
He says the government has been telling people the state's underground water stores are being managed sustainably.
But in truth it has no idea of the cumulative impact if all nine Galilee basin mine proposals, including Adani's, proceed.
"We're looking at extraction of four Sydney Harbours out of underground systems. That's a huge amount of water," he told ABC radio on Thursday.
"We see politicians put their hands on their hearts and tell Queenslanders that we're managing our groundwater resources sustainably
"They don't know ... the Queensland government doesn't have a clue what's happening in terms of how underground water is being managed."
He said the state government only began forcing miners to measure or estimate their use of underground water in December 2018.
"We have not seen any reports on that."
He said the government should never have allowed Adani's mine proposal to proceed as far as it has.
"What we're really facing here is we're facing an attack on science, versus the politics of jobs."
Mr Crothers said 270 gigalitres, or 108,000 Olympic swimming pools, would be lost over the life-span of the Adani mine.
He repeated concerns raised by other water experts that the company's hydrological modelling is dubious.
Hydrologists have warned the mine could rob the nearby Doongmabulla Springs Complex of its underground water source and kill off dependent ecosystems.
There are also concerns groundwater disruption could rob the Carmichael River of water that keeps it flowing for much of the year.
Adani has said its water plan is the result of years of work, involving a huge amount of scientific work.
It says it will trust the views of regulators tasked with assessing the plan.
The state environment department has not said when on Thursday it will release its decision on the plan.
It's the last approval Adani needs to press on with mine construction.
