A dusty, red-soil farm with a corrugated iron windmill pumping in the middle of it is a classic image of Australian folklore. But what the windmill is pumping — groundwater — remains a tumultuous issue in Australia water management; particularly in light of the new draft Murray-Darling Basin Plan.

The use of groundwater is “a major determiner in Australia’s future when it comes to water”, according to professor Craig Simmons, director of the National Centre for Groundwater Research and Training. Simmons is one of several world groundwater experts meeting in Sydney for a three-day conference this week.

Groundwater is exactly what it says it is, water that lays under the ground and can usually only be accessed by pumping. But this isn’t any old water, it’s water in underground storage facilities that have filled up over thousands of years. These days it makes up about 20% of the world’s drinking water and 30% of Australia’s total water use.

Groundwater was raised as a key problem with the latest Murray-Darling Basin Plan guide in a 25-page report released by the Wentworth Group of Concerned Scientists last week, where they noted the issue of groundwater over-allocation and the lack of research conducted on what impact increased groundwater extraction will have in the basin.

Currently about 1744 gigalitres of groundwater are extracted from the Murray-Darling Basin per year. The 2010 guide to the draft plan recommended a decrease in that usage by 160 gigalitres. In contrast, the new draft plan calls for an increase in groundwater usage by an additional 2760 gigalitres per year, taking it to a total of 4340 gigalitres of groundwater being extracted from the basin. But there’s been no reason given for the “major U-turn” in groundwater policy from the 2010 guide, says Simmons.

“The lack of justification for such large changes to groundwater extraction levels raises serious concerns about the groundwater extraction levels in the draft basin plan and the decision to not include an analysis of groundwater reductions in the surface water model,” said the Wentworth Group in its report released last week.

Simmons agreed with the criticisms raised by the Wentworth Group, declaring: “It’s absolutely clear that the Wentworth Group has got it right, they’re spot on in their analysis of that document.”

For Simmons, the groundwater changes without scientific justification raise “real issues around trust, confidence and transparency” in the Murray-Darling Basin Plan and Authority.

“It really does beg the question about our confidence in the project and its ability to deliver ultimately what it needs to, and that is a healthy, working river system,” added Simmons.

In Australia, groundwater is mainly used for irrigation, agriculture, mining (including coal seam gas) and drinking water in regional areas. “We’ve got to husband the groundwater resource with great care if and when we need them,” said Simmons, noting the huge social, economic and environmental demands on it.

Professor Robert Glennon, from the University of Arizona and author of Unquenchable: America’s Water Crisis and What To Do About It, explained that, in 1965, 8 billion gallons of groundwater were pumped per day in the United States. In 2005 (the most recent time period available for groundwater data in the US) that figure had grown to 80 billion gallons a day. Half of the United States is reliant on groundwater for drinking.