Australia — Run-off from bushfire-hit areas of Victoria is contaminating the Yarra River with a black sludge, which poses a threat to fish and wildlife like platypuses.
Environmental groups say they willl be closely monitoring Victorian waterways as sediment from the bushfires flows downstream and out to sea.
Following heavy weekend rainfall in some parts of the state, ash and debris are making their way into creeks and the Yarra River.
There are more than 900 kilometres of waterways in the burnt out areas likely to be affected.
Authorities will be looking at the possibility of releasing water from storages to flush out the waterways.
Environmental Protection Agency chairman Mick Burke says while river life will initially be disrupted by the bushfire sediment, marine species are expected to survive the polluted environment.
He says there are always concerns there will be some impact after sediment enters the catchments.
He says ash in the water will impact on freshwater life.
“We did some studies after the bushfires in 2003 in the north-east of the state and we found that those ash flows and sediment flows into streams do disrupt the life that lives in those streams,” he said.
“In fact we could find very little [life] straight after the ash washed in.
“But within 12 to 18 months it returned to almost the same conditions as prior to the bushfires so the recovery should occur.”
He says recovery of marine life in the river systems should be seen within a period of one to two years.
“It is a peak event, it does have an impact but that impact, as nature often does, reverses itself over a reasonable period of time,” he said.
Over the weekend the Victorian Opposition said the most recent measure of faecal pollution showed massive levels of bacterial contamination over the past fortnight, with samples exceeding acceptable levels at every sampling point on the river.
Mr Burke says it is not unusual for the Yarra to be highly turbid after big rainfalls.
“We keep a close eye on faecal contamination in the Yarra River as one of the indicators of health for recreational pursuits on the Yarra,” he said.
“We do know that there are high numbers after rainfall just before Moomba, as would be expected after a long dry period and a sharp rainfall event.”
“I can say that as of last Wednesday, they were back to normal.”
Melbourne Water’s general manager of waterways, Chris Chesterfield, says people will see some dramatic changes in the Yarra River as some streams turn black.
“It’s ash, it’s sediment, it’s organic material,” he said.
“That fine material can coat the gills of fish and make it difficult for them to breathe. The organic material can lower oxygen levels in the river which again has an effect on the fauna.”
He says longer term that can lead to algal blooms.
He says authorities are keeping a very close eye on water quality.
“If we get a combination of lot of input during a time of low flow, then there is the potential for fish kills,” he said.
“We have both scientists and community members out there looking at the most vulnerable areas so that if we start to see those sorts of things happening, then we can respond.”
Authorities will be keeping a close eye on platypus numbers.