If drying trends continue, groundwater recharges into a key WA aquifer will stop and allocations will be cut, according to a Western Australian Government review.
The Department of Water and Environmental Regulation (DWER) conducted a review into the amount of water which could be sustainably taken from the Mingenew Parmelia aquifer.
It followed a failed bid by the Chinese miner Karara to increase its water entitlement from the current five gigalitres per annum to seven.
The review found all water users in the aquifer may have their water licences reduced if rainfall continues to decline.
The Department will now conduct a three year review into the Arrowsmith Groundwater Allocation Plan from 2010.
This Plan defined water availability, allocation, and management across 10,000 square kilometres of land in the Northern Perth Basin.
Arrowsmith's southern boundary is about 200 kilometres north of Perth, extending to just north of Geraldton. It contains seven sedimentary and fractured rock aquifers and has 184.9 gigalitres accessible for licensing.
It is a region with diverse water users — from public water for Geraldton and Jurien Bay to miners, horticulturalists, grain farmers, and graziers.
"We recognise that it is time that is reviewed, and we are going to incorporate allocation limit reviews into that," DWER program manager of water licensing Fleur Coaker said.
"We will look at climate data across the region and factor that in."
Mingenew aquifer case study in a drying climate
Karara Mining already has a licence for five of the 5.4 gigalitres available for licensing in the aquifer.
Ms Coaker said aquifer allocation limits were determined by recharge, with a percentage of water reserved for environmental and cultural purposes, public water supply and stock and domestic purposes.
She said rainfall in the area has reduced from 400 millimetres to 350 millimetres since 1960 to today.
After rising from 1966 to 2015, groundwater recharge of the aquifer had now plateaued.
"From now until 2050, recharge is forecasted to significantly decrease, with little to no groundwater recharge occurring, should the average annual rainfall go below 300 mm per year," the report stated.
"As a result of the drying climate, the long-term reliability of supply for existing users is expected to decrease over the next 30 years."
Ms Coaker said the Department would monitor the groundwater and climate.
"If we got to that point of 300mm [of rainfall] a year then things are going to have to change," she said.
"There has to be cuts from taking water out of the ground … [extraction from the] aquifer will need to have reductions."
Mine used precious water to wash rocks: local farmer
Mingenew farm manager Ben Cobley was one of a group of farmers adamantly opposed to Karara being granted its water licence in 2011.
His farm records show rainfall decline in the region, and he wants to see natural springs in the area protected.
"I say this with respect, but there wasn't a lot known about the Parmelia in our view," Mr Cobley said.
"So for a private entity to be granted a very large percentage, upwards of 80 per cent of the allocation of that aquifer, it was a ludicrous proposition at the time.
"And I probably haven't changed my view on that.
"They were getting this pristine, perfect, potable water, they were taking all of it from the aquifer beneath us, and shipping it 145km away and as far as I'm concerned, using it to wash rocks.
"This water should be used for drinking and agriculture."
Miner told to drill deeper
Ms Coaker said Karara was recommended to conduct a H3 hydrogeological report into taking its additional water requirements from the Yarragadee aquifer, which sits beneath the Mingenew Parmelia.
"They're looking at other sources of water for their long term mining needs, and one of those options is to take water from the Yarragadee Aquifer, which is much deeper," she said.
"The quality is probably not as good but there is no demand from that aquifer in that area at the moment."
However Ms Coaker said the department was considering allowing Karara to temporarily take an additional small volume of water out of the Mingenew Parmelia Aquifer.
"Under the existing allocation limit there was 400,000 kilolitres still available, so we are looking at Karara being able to take that small volume of water for a short period of time, for a maximum of five years," she said.
"That licence would be non renewable, so that's still under assessment at the moment but we have expressed that as an option for them."
The ABC contacted Karara however the company did not wish to comment.
First in, best dressed
Groundwater in Western Australia is licensed under a 'first in, first served' policy.
If an aquifer is fully allocated, existing licence holders may transfer or trade all or part of their water entitlements to third parties.
Mr Cobley said this was stifling potential agricultural projects in the region, such as horticulture or irrigated grazing.
"If you were an investor or an entrepreneur and you were thinking that you'd like to use some water to create a start up industry in the Mingenew area, you've got to have some security that you have tenure over that water," Mr Cobley said.
"What's left after Karara has taken it all, you're just not going to make that investment, you'd be mad to!
"There's no water there for you to take."
Environmental allocation increased
Under the review, water reserved for environmental and cultural purposes will be increased from 10 to 35 per cent.
It found there was sufficient public water supply to maintain the town of Mingenew, Morawa, and surrounding communities until the year 2050.
"The Irwin and the Lockier Rivers are a significant heritage site for the Aboriginal peoples of this area," the DWER review said.
"The Southern Yamatji people [Amangu, Naaguja, Mullewa Wadjari and Widi mob claim groups] are the registered Native Title claimants over the Mingenew sub-area.
"The Geraldton Area Settlement Agreement for Native Title is currently underway.
"This agreement will determine and register an Indigenous Land Use Agreement for the claimants, recognising the traditional owners of the land and waters in the area."ABC