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Drinking water search in NSW's central west to use aerial electromagnetic method

Jennifer Browning and Olivia Ralph, Monday October 7, 2019 - 09:24 EDT
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Martin Knoesen flies the chopper that carries the electromagnetic sensor that is used to detect groundwater sources. - ABC

The New South Wales Government has funded a large aerial search for groundwater in the state's central west in an attempt to secure drinking water for regional communities at risk of running dry.

The aerial electromagnetic survey searches for groundwater and minerals about 500 metres beneath the earth's surface.

The survey is covering 19,000 square kilometres — an area about one and a half times the size of Greater Metropolitan Sydney.

Director of Geoscience Information at the Geological Survey, John Greenfield, said the sensor, towed by a high-performance helicopter flying at a height of about 60 metres, worked much like the metal detectors often seen at the beach.

"The transmitter in the sensor sends out an electromagnetic signal that interacts with the soil, rocks and water below and is returned and measured by the sensor, with the strength of the return signal providing an indication of what might be located below," Dr Greenfield said.

"They do call this the metal detector of the sky."

Success expected

A daily helicopter mission traces the region, from south to north on east-west lines up to 5km apart, covering areas from Cobar to Rankins Springs.


The technique has been successfully used in South Africa and in the US.

"I think we will definitely find water. We know there are groundwater sources in the survey area, especially down near the Lachlan River," Dr Greenfield said.

Pilot Martin Knoesen said he was very confident it would work.

"It was recently used in Cape Town to find aquifers," he said.

"There was the biggest drought in living memory and they got some good data from that."

Data collected from now until November will be analysed and formulated into a report due to be released early next year, which will be made available to farmers throughout the region.

Cobar farmer Anita Burcher spent $20,000 in recent years drilling two bores unsuccessfully, but is hopeful the information gathered would make a strategic third attempt successful.

"It's a way to save us a lot of money by not looking for holes that are dry," she said.

"We put down two holes; they went to 200 metres and blew dust so all that money for no return at all."

'We can do better'

NSW Deputy Premier John Barilaro said the aerial electromagnetic survey "took out the guesswork about where we punch bores or where there might be water, and in this drought I think we have to do everything".

He openly acknowledged the mistakes of past governments, and believes they can "do better".

"I think in the middle of every drought we talk about building dams and water infrastructure; the rain comes, we stop," he said.

"I think the lessons of the Millennium drought weren't learned — this time we're learning."

Dirt channel keeping two towns alive

Ageing infrastructure further compounds water shortages in the state, especially the western region.

The Albert Priest Channel keeps the towns of Cobar and Nyngan alive.

It was built in 1942 to carry water from the Macquarie River to Nyngan, before it is then piped to Cobar.

Up to half of the water carried through the 60km channel is lost to leakage and evaporation.

"That has been a thorn in my side for the last 19 years as Mayor of Cobar," Mayor Lilian Brady said.

"We lose 50 per cent and we pay for that."

Mr Barilaro acknowledged the scale of the problem and said both a short and long-term solution was being sought to fix the channel.

"We're putting in a $1 million bandaid approach to fix [it] but the long-term [plan] is to replace the channel," he said.

"It's an $85 million project we're pursuing at the moment.".


© ABC 2019

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