Nine planned coalmines would threaten future of dozens of farming communities, lobby group Lock the Gate says

Nine planned "mega-mines" in the Galilee basin region of Queensland would drain the area of 1,354bn litres of water, equivalent to two-and-a-half times the volume of Sydney harbour, threatening the future of dozens of farming communities, a new report has found.

The study, undertaken by the anti-mining network Lock the Gate and overseen by Tom Crowthers, former general manager of water planning and allocation for the Queensland government, says the mines could cause "unacceptable impacts" on the region's groundwater and surface water resources. Crowthers said communities would be affected "forever" if all the projects were to go ahead.

The six-month analysis found that a majority of the 200 water bores within the mine lease areas would become inoperable should the projects go ahead. One mine, the South Galilee project, could cause groundwater levels to drop by 70 metres.

The water would be lost because coal seams are located beneath the natural aquifers, requiring miners to release vast amounts of water to access the resource. The report predicts that 50bn to 70bn litres of water a year will be needed by the mines for washing coal and other operations. A lack of water is now being felt by the Queensland cattle industry, with some warning that 80% of the state could be in drought within weeks.

Lock the Gate's report is compiled from publicly available environmental impact statements for five of the mines, with these figures used to extrapolate the impact of the other four mines.

The mines, which would consist of 34 open-cut pits and 11 underground mines along a 270km strip of central Queensland, would produce more than 300m tonnes of coal a year – doubling Australia's annual coal haul for export.

Only one of the mines – the Alpha joint venture project backed by Gina Rinehart's Hancock Coal – has been given full state and federal government approval, although it faces a legal challenge over its impact on groundwater.

The other eight mines are in various stages of the approval process; Clive Palmer's Waratah Coal has won state government backing for its vast China First mine.

Under legislation passed in the final months of the federal Labor government, projects that will significantly impact the water table must be first assessed by the federal government. The environment minister, Greg Hunt, has said 50 projects have been left in "paralysis" by not being assessed under this so-called water trigger. He has pledged to speed up the process of environmental approval, handing power to state-run "one-stop shops".

Lock the Gate said an immediate halt had to be placed on the proposed Galilee basin mines until a full assessment could be conducted to ensure groundwater wasn't adversely affected.

"This is a desert region that's highly dependent on groundwater, so dozens of farming properties will be impacted by these mines, as will the people in the towns of Alpha and Jericho," Ellie Smith, Lock the Gate co-ordinator, told Guardian Australia.

"It's now dawning on people what the impact of these mines will be on them. A lot of them have trusted the government but are now realising the situation isn't fair. The mining companies have legal requirement to look after the surrounding graziers.

"This is now a huge test for the new government to see if it will use the new water trigger power by taking the evidence seriously. They have had a lot of rhetoric about allowing landholders to say no to mining, so it will be interesting to see what they do."

Jeff Seeney, the deputy premier of Queensland, rejected the Lock the Gate report, saying a "rigorous" approval process would soon be supplemented by new monitoring of groundwater systems.

"Lock the Gate and [its president] Drew Hutton are against any resource development ... and are working constantly to undermine industries which provide tens of thousands of jobs to Queenslanders and substantial revenue to the state and federal governments," Seeney said.

"Their attempts to undermine development in the Galilee basin are part of a national co-ordinated campaign by various radical green groups to shut down the coal industry.

"Everything they say or do has that goal as their focus. Their most recent claims need to be viewed on that basis.

"Major coalmine projects have been part of the Queensland economy for decades and have provided substantial benefits to regional communities and the state as a whole.

"They operate to strict environmental standards – as will any future mines in the Galilee basin."