‘Smells like sewage’: blackwater from Victorian floods causes mass fish deaths

4 months ago 20

Peter Phillips has spent a lot of time in blackwater.

He paddled 2,000km over50 days along the Murray River during the 2016 floods. Most of that was in blackwater, an event often caused by flooding when high levels of organic material are washed into the river systems, and which “basically sucks all the oxygen out of the water” as it decays.

He knows what it looks like, smells like, even tastes like.

But the Echuca environmental science teacher said this time things are “unusual”. The blackwater is different and “smells like there is sewage in it”.

The fish and animals are dying en masse. It is a toxic, painful death.

“The fish deaths in the Murray at Echuca are unusual. It does not appear to be a case of the ‘usual’ blackwater,” he said.

Phillips believes the low levels of dissolved oxygen (DO), which caused “massive fish kills” along parts of the river system, are from sewage leaks upstream.

“The fish are definitely suffering and many have died,” he said. “There are sightings of [crayfish] crawling out of the river.”

“One person said even the turtles are dying and they don’t even breathe the water. I think it’s a really high bacterial load, just a really unhealthy soup.”

Rescued Murray crayfish will be released once water quality in the Murray River improves. Swan Hill, NSW.
Rescued Murray crayfish will be released once water quality in the Murray River improves. Swan Hill, NSW. Photograph: The NSW Department of Primary Industries (DPI)

In response to community concerns about contamination in the water after widespread flooding across the state, the Environment Protection Authority (EPA) Victoria has launched a “high quality” sample analysis program.

The state’s chief environmental scientist at EPA Victoria, Prof Mark Taylor, said the EPA’s advice remains: stay out of the water.

“When the whole land is inundated, it will inundate, release and mobilise sewage, which is why we’re measuring for E. coli,” he said.

Taylor said this is new territory and a national first for the EPA.

“I do believe no other EPA has gone out and done this sort of work like this before in Australia,” he said.

The EPA’s warning comes as experts flag warming temperatures combined with flood waters could be the perfect storm for a Japanese encephalitis outbreak.

Before he was a high school teacher, Phillips was a biologist and is currently doing his PhD on the interaction between hydrology, geomorphology and ecology during flood events.

Phillips suspects major flooding in Shepparton in northern Victoria contributed to significant fish deaths over hundreds of kilometres, including his home town in Echuca.

“When the fish deaths started to happen, the water was actually quite milky brown, and that’s sediment rather than tannins that are associated with blackwater events, hence the colour,” he said.

Based on the data from DO meters at hydrological stations at McCoy’s Bridge and the Barmah-Millewa forest, Philips could pinpoint the sudden drops in DO levels with the arrival of the flood water from Shepparton.

Biologist and environmental science teacher, Peter Phillips, sampling the blackwater in the 2016 flood, Swan Hill, Victoria.
Biologist and environmental science teacher Peter Phillips sampled the blackwater in the 2016 flood. He says this time things are ‘unusual’.

“There was major flooding there for seven days from 16 October. Over 1,000 homes were inundated, exposing the flood waters to sewage,” he said.

“Perhaps this would be enough, even if the sewage treatment plant was not affected.”

The general manager of Goulburn Valley Water, Daniel Flanagan, said the widespread nature and impact of this flood was unlike anything he’d seen before.

He said part of their storage network was inundated and affected by flooding, particularly in Shepparton.

“So with that being inundated, obviously there is some leakage from that sewerage network.”

However, Flanagan said the sewage treatment plants in Shepparton and Mooroopna were not inundated by floods.

“But because of all of the flow coming into our sewage treatment plant, we had to do what we call an emergency discharge, but at a water quality which is referred to as Class C,” he said.

“It’s been through the full treatment process before we discharge that.”

According to Phillips, there have been “massive fish kills” all along the Goulburn, Broken and Murray rivers and their anabranches as the flood water travelled north from Victoria and into New South Wales.

“The most sensitive fish are Murray cod – they are usually the first to die and they haven’t been in this case.”

Phillips said the first has been “a flood specialist” called yellowbelly, also known as golden perch.

Peter Phillips on his journey kayaking along the Murray River sampling the blackwater in the 2016 flood, Barmah Forest.
Phillips’s kayak on the Murray River in 2016. Photograph: Peter Phillips

“So to see the yellowbelly die in supposed blackwater is really quite unusual. It’s their medium, it’s the thing they’re adapted to.”

He said the cod are dying too, but after the yellowbelly, and there would be about 15 yellowbelly to one cod in the Murray River at Echuca.

“It’s different in a few other places but it’s unusual,” Phillips said.

“The smell has been noticed and the fish deaths, yes, yellowbelly seem to be the ones going first. It seems to be a consistent thing.”

Taylor said the EPA are working with the NSW State Emergency Service (SES) and using “super high-quality, ultra-trace detection” after they received some additional government funding.

Regional sample locations include townships such as Echuca, Swan Hill, Shepparton, and Rochester.

He said the EPA are sampling for a range of unusual contaminants such as endocrine disruptors, personal and pharmaceutical care products, along with pesticides and other trace elements.

“But some of those elements or compounds are likely to have leaked from sewage treatment systems or flushed off from agricultural sites,” he said.

“We think about the people who live in rural areas and they’ve all got onsite septic tanks and seepage trenches.”

Taylor said they know, from the analysis of both sediment and water from ongoing operations, it is likely there’ll be “higher levels of E. coli” bacteria, which is an indicator pathogen.

But he said the good news is that as the flood water recedes and the pathogens are deposited on the surface, the UV will “ultimately terminate the prevalence of the E. coli”.

  • In NSW, to report areas where fish may be struggling or fish deaths have occurred, call the NSW Fisheries hotline on 1800 043 536. In Victoria, community members can report fish deaths to the EPA’s pollution hotline on 1300 372 842.

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