Perfect storm for toxic acid plumes in NSW rivers

In the wake of heavy flooding, poisonous acid plumes are beginning to form in coastal rivers across New South Wales causing severe environmental damage, UNSW researchers warn.

Cattai Creek draining into the Manning

Acid plumes forming in the Manning River in Taree, NSW (Credit: Brad Diebert)

In the wake of heavy flooding, poisonous acid plumes are beginning to form in coastal rivers across New South Wales causing severe environmental damage that will continue unless natural wetlands are restored, UNSW researchers warn.

As floodwaters drain from agricultural lands back into tidal rivers, large volumes of sulphuric acid are released from the soil and transported into the rivers, along with toxic levels of iron, aluminium and other heavy metals that can kill fish, oysters and other marine organisms.

“The acid in these soils has been created by the historical practice of draining wetlands,” says Dr William Glamore, a Senior Research Fellow at the Water Research Laboratory at UNSW. “The prolonged dry season combined with heavy rainfall recently has created the perfect storm for acid plumes.”

“If this was a factory releasing acid it would be hundreds of tonnes worth pouring out into an estuary and there would be mass media coverage and a major clean-up effort.” he says. “It’s car battery levels – you shouldn’t swim in it, you shouldn’t touch it, or go near it, yet it’s not being publicised.”

Glamore says the plumes can extend down river for tens of kilometres, moved by the tides, and often turn orange because of the high iron concentrations. He says they are damaging to the environment and major fish kills in coastal rivers have previously been reported in NSW. 

“An ideal pH level for coastal rivers is above seven, which is neutral. A bad level is five, and we’re seeing these rivers down between pH levels of two and three, which is at the extreme end,” he says.

Glamore and colleagues from the UNSW Water Research Lab, part of the School of Civil and Environmental Engineering, have been monitoring a stretch of the lower Manning River in Taree, NSW – one of the first rivers in the state to turn acidic. Their aim has been to measure the acid event as it develops and track the acid plume down the river, which they have been doing with high-precision probes and aerial surveys.

“While we know acid discharges occur after flood events, limited efforts are undertaken to measure the plume or assess the environmental damage,” he says.

Glamore says the solution is to restore degraded wetlands back to their original state. He has been involved in successful restoration efforts at other acid sites in the Shoalhaven, Hunter, Clarence and Tweed Rivers, where significant improvements in water quality have been recorded. 

“These projects typically involve restoring tidal flows or redesigning the landscape to reduce and neutralise acid at its source,” says Glamore. “A prioritised network of restoration sites is immediately required along with sufficient funds to return these sites to healthy wetlands.”

The Greater Taree Council and Wetland Care Australia have both assisted the UNSW researchers with their project on the Manning River.

Read the story in the Sydney Morning Herald

Media Contact: Myles Gough, 0420 652 825,