THE latest flood event, while causing untold damage to local roads and properties, has actually been a godsend for the acid sulphate soil problem of Cattai Creek in the lower Manning.
"We are very lucky that all this rain of late has helped to dilute the acid from this catchment, otherwise things could have been a lot worse," Greater Taree City Council's senior environmental planner Tanya Cross said this week.
She was commenting on the story 'Acid plume poisons river after floods' (SMH Thursday February 28), in which the Herald's environment editor Ben Cubby claimed swimming in, and drinking water had been "temporarily banned in sections of the (Manning) river and other aquatic life is expected to be largely wiped out", by a poisonous plume of acid "comparable to car batteries".
Ms Cross confirmed on Monday that council has not been notified by any health authority that swimming in or drinking water from the Manning River has been baned.
"While it's definitely not as bad as the SMH article made it sound in regards to the Manning River itself, the pH levels we have been recording in Pipeclay Canal have been around 2 3, which is extremely acidic," she said.
She added that she "wouldn't be touching the water in the Pipeclay Canal", and while pH levels are still low in Cattai Creek (between 3 and 4), they are not as bad as in Pipeclay Canal.
She said a pH of 5 was recorded last week at the Cattai Creek junction with the Manning River, which would be impacting on water quality but thankfully diluted by the latest flood flow in the river.
"Council has recently been successful under the Hunter-Central Rivers Catchment Management Authority's Partnership Program for funding to assist with land acquisition and acid sulphate soil remediation within the Big Swamp project area," Ms Cross said.
"Representatives from the NSW government, including the Soil Science Division of the Office of Environment and Heritage, the Hunter-Central Rivers Catchment Management Authority and National Parks and Wildlife Service have also been actively involved in the management of the Big Swamp/Cattai Wetlands projects through their participation on council's Manning Wetlands Steering Committee."
She said that while council's Cattai Wetlands project has helped to reduce the amount of acid runoff entering Cattai Creek from that sub-catchment, the adjacent Big Swamp area is just as bad as ever in terms of acid suplhate soils, "which is why we are working so hard to fix it".
In response to the SMH article, the Times on Thursday sent a photographer and journalist to check the situation in Cattai Creek ('River healthy despite reports' MRT March 1-2), and had reassurance from oysterfarmers the Stone family that the river pre-flood is in the best shape they have seen it, thanks to council's continuing Big Swamp/Cattai wetlands project.
The Herald article on the Manning River's 'acid plume' was prompted by a University of NSW media release last week warning of poisonous plumes beginning to form in coastal rivers across New South Wales in the wake of recent weather events, causing severe environmental damage that will continue unless natural wetlands are restored.
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," Dr William Glamore, a senior research fellow at the Water Research Laboratory at UNSW said.
"The prolonged dry season combined with heavy rainfall recently has created the perfect storm for acid plumes.
"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."
He referred to major fish kills previously reported in NSW coastal rivers.
"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 and colleagues from the UNSW Water Research Laboratory have been monitoring a stretch of the lower Manning, their aim being 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.
He said the solution is to restore degraded wetlands back to their original state, which Greater Taree City Council has been doing since starting its Cattai Wetlands/ Big Swamp project several years ago.
Contacted by the Times on Monday, Dr Glamore was unaware of any 'ban' on swimming in or drinking water from the Manning.
"What I said was that I would certainly not want anyone from my family drinking, swimming or recreating in the river."