Saturday, 10 November 2012

Wheatbelt’s salinity worsens with acidification

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Western Wheatbelt_salinity“There is a significant amount of work that needs to be done to try and stop this.”—Dr Degens. Image: SCIENTISTS have discovered the Wheatbelt’s groundwater is not just salty but also acidic—a rare problem that is impacting waterways and farmland in the region.

For more than four decades, farmers have been fighting salinity in areas where land clearing has caused the groundwater to rise.

But now, Department of Water chemist Brad Degens has found the issue is more complicated.

Dr Degens and his team have spent seven years collecting more than 1000 water samples from 406 creeks and lakes in the Avon Basin and were surprised to find shallow groundwater in the area is acidic as well as saline.

Dr Degens says the acidity is a natural product of WA’s ancient landscape and slow-moving groundwater.

The problem is land clearing for agriculture has brought the groundwater to the surface.

“The combination of acid and salinity in groundwater is a rare thing,” Dr Degens says.

“It is unusual in a world-wide sense, most other areas in the world where there are salinity problems you don’t tend to have acidity as well.”

The scientist’s findings were published in the peer-reviewed Journal of Hydrology in September.

Dr Degens says farmers tackling salinity have inadvertently made the acid problem worse by building groundwater drains to divert water down away from farmland.

The drains, which are 2m deep, are concentrating the acid waters, which then overflow, leaching acidic waters into nearby creeks and lakes.

“There is a significant amount of work that needs to be done to try and stop this,” Dr Degens says.

“We are only just coming to understand this and a lot of people aren’t aware that a certain amount of the groundwater is acid and things like drains will change how that gets to the surface.”

He says there are things farmers can do to try and curb the problem, like planting more trees and treating the water in drains.

Dr Degens says that while the acid isn’t good for waterways, a lot of the damage to freshwater species living in creeks and lakes has already been done when salinity first became a problem.

As part of the study, the researchers found that while waterways north of Merredin were impacted by rising groundwater, some places, such as the Lockhart River near Bruce Rock, were more severely impacted because of drains.

“One of the spin-offs from this is that where we have naturally acidic lakes, we’ve had interest from people in the US basically using the lakes as Martian analogues because there is a connection between some of the minerals they found on Mars and some of the same minerals in the WA lakes,” Dr Degens says.

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