Like all precious resources, water is finite.
CSIRO scientists and researchers work on technologies and methodologies to advance the circular economy for mineral resources, so too are they finding ways to make the most of every drop of our water.
Regional Australia bears the brunt of the nation's extreme weather, which is increasing in frequency and severity because of climate change.
That's why CSIRO recently launched its Drought Resilience Mission, which aims to reduce the impacts of drought in Australia by 30 per cent by 2030.
Dr Declan Page is a groundwater systems expert at CSIRO working on key Drought Resilience Mission projects.
He's spent more than 15 years working on Managed Aquifer Recharge (MAR) and water banking.
"We take available sources of water – natural river water, mine water, industrial water, wastewater, urban stormwater – recharge it into an aquifer and then recover it later for beneficial use."
Aquifers are natural underground reservoirs, storing water in porous or fractured rock or loose sediments.
The recharge process can be achieved either by natural infiltration, via a shallow depression in the ground, or injected by pumping it into a deeper aquifer via a well.
Aquifers in action
There are urban, regional and remote MAR demonstration projects underway, and several that are well established.
"For example, here in Adelaide, where I live, the local councils inject urban stormwater into a brackish aquifer 200m deep, and recover it in summer for greenspace irrigation," says Dr Page.
"That's been going on now for decades."
Another project in Perth puts purified recycled water into a deep aquifer.
"Rather than build another seawater desalination plant, it is cheaper to recycle treated wastewater via aquifers," explains Dr Page.
"It is treated to a very high degree – even beyond drinking water standard – and injected into the same drinking water source aquifer to replenish the groundwater."
This groundwater replenishment scheme stops the decline of groundwater volumes.
"It takes about 50 years from the point of injection of the recycled water for it to reach the point of recovery for drinking water. The public is quite comfortable about that now, and there’s no longer a focus on the source of the recycled water."
Learnings from such projects in urban areas are now being taken to the regions, although the technology is in some ways the easy part.
"The biggest limitations in Australia are the economics and the variable policy environment, rather than how to get water into and out of the ground, but if we can bring water banking from boutique to mainstream we will enhance regional areas’ resilience to future droughts."
Exploring water opportunities in the Pilbara
The far north-west of Australia is famous as iron-ore country, and beneath the red dirt are numerous aquifers, home to groundwater and potential MAR storage systems for mine dewatering and run-off from cyclonic rainfall.
"The WA Department of Primary Industries and Regional Development (DPIRD) set up its Transforming Agriculture in the Pilbara (TAP) program to review water availability, soil quality and agricultural opportunities in three selected regions of the Pilbara," says Dr Olga Barron, CSIRO groundwater management expert.
"One region is close to Newman, Eastern Pilbara's main town."
Mining operations in the region date back to 1968.
"In the Pilbara, rainfall can be substantial at times, but it's infrequent and any long-term irrigated agriculture development would need reliable water," says Dr Barron.
DPIRD wants to discover if aquifers in the area are suitable to be replenished, either from those brief periods of heavy rainfall, but more likely from "mine dewatering".
"In the Eastern Pilbara, there are a number of different miners along the ridge and a lot of the ore at this stage is below the water table," explains John Simons, Senior Research Scientist in DPIRD's Water Science group.
He's been working with CSIRO and various mining companies to assess the environmental and technical feasibility of taking surplus water from mining operations and storing it in aquifers for irrigated agriculture.
"Most of the currently mined iron ore deposits in the region are associated with aquifers, so they need to remove quite a substantial amount of water to reach them," explains Dr Barron.
"We approached BHP to let them know about the project – looking for MAR opportunities that would store water to be used later for irrigation. They were happy to be involved – as they plan expanding mining operations, they will have even more water surplus."
Drilling into the details – and the data
With the support of BHP, scientists have been working since 2019 "on the characterisation of the groundwater systems of the region to understand the MAR opportunities", says Dr Barron.
"It's a data-poor area – very little is known about the underground structures of aquifers, which is critical in order to understand how effective MAR could be," she says.
"BHP has co-funded some geophysical surveys and drilling programs to help us better characterise the systems, because while there are general guidelines for MAR, when it comes to establish a scheme, you need that site-specific knowledge."
Mr Simons says that Dr Aaron Davis, Principal Research Scientist and Team Leader from CSIRO's Mineral Resources managed an airborne electromagnetic survey.
"We focused on an area that doesn't have mining prospects, so there'd be no land conflict," explains Mr Simons.
"They did the data acquisition and processed it to give us an idea of where to look for MAR opportunities."
Following that, CSIRO's Dr Mike Donn, Senior Experimental Scientist and water specialist, came to the aquifer party.
"He will run the data against the Australian guidelines for MAR – and look at whether it is actually feasible out north of Newman to tap into the mine dewatering surplus, and put it into the ground for later use," says Mr Simons.
Mr Simons says that the mining outlook in the area for at least another 30 years, and that as the dewatering volume increases, so will the potential "to use that water beneficially in irrigated agriculture".
More CSIRO scientists are working on the geophysics, hydrology and geochemistry to better understand the characteristics of the aquifers they're identifying.
"The use of environmental tracers, such as noble gases, and naturally occurring isotopes in the water, is very useful," says Dr Barron.
"The combination of those tracers allows us to infer what kind of replenishment is already happening, how aquifers are connected or disconnected, historical flows and how quickly the groundwater is moving. If it's moving too fast, you might not be able to store much water. We have to integrate all that data."
CSIRO groundwater modellers will help DPIRD determine the physical feasibility of storing water in the aquifers.
"We need to know whether it will 'mound up' for us so we can extract it later, or if it will go sideways and disappear," says Mr Simons.
"We're still working through that one!"
They must make sure that the stored aquifer water wouldn't be so shallow as to allow the surface vegetation to access it, but also big enough for extraction, and not too deep so as to make it uneconomic.
"We make sure we have no adverse effects on current users, the environment or cultural heritage," says Mr Simons.
How about a Pilbara peach?
Mr Simons jokes that he stays sane because he's doing land and water assessment, but the next steps on the economics and proof of concept fall to his DPIRD colleague Dr Chris Schelfhout, project manager for the TAP project.
"For some years we have been proving up land and water resources for prospective irrigated agricultural development in the Pilbara," Dr Schelfhout explains.
"TAP is looking at irrigated crop opportunities right across the Pilbara, but there are significant climate differences between coastal parts of the Pilbara and the inland, more elevated regions, such as the Newman area."
"Recognising that the winter nights are particularly cold in Newman, we decided it may be possible to grow stonefruit and high-value horticultural crops," he says.
The dream would be to grow for the domestic out-of-season market and replace some US imports.
A proof-of-concept test site was planted out at Martu Farm near Newman in 2018, with fruit trees, horticulture crops and a range of field crops, including lucerne, sorghums and millets and temperate cereals such as wheat, oats and barley.
"We've had some quite exceptional yields, including triticale varieties that yielded the equivalent of close to 10 tonnes per hectare," says Dr Schelfhout.
"We're getting better insights into what crops may be a good fit for that Newman location, where we would use surplus mine dewater and MAR as irrigation. We believe there's potentially tens of gigalitres of water available for irrigation, which could allow between 1000 and 3000 hectares of irrigated ag development in the area, so it's quite significant."
The test crop of stonefruit "wasn't overly scientific", says Dr Schelfhout.
"It was a case of putting them in the ground, fertilising and watering them, seeing if they went through that natural cycle of going to dormancy over winter, when are they flowering, when are they fruiting, and how does that align with possible market opportunities".
This October, the plan bore fruit, literally.
"We had a good crop of peaches and nectarines," says Dr Schelfhout.
"More agronomic research needs to be done to see how early we can push that cropping season to capitalise on the out‑of-season market or to replace imports, but some of these young trees were laden with fruit, no significant pests or diseases. And they were really good to eat!"
It's no surprise: The circular economy always tastes sweet.