TESTS carried out on Central Queensland’s Fitzroy River following the deaths of thousands of fish have found reduced oxygen levels caused the deaths.
Environment Minister Andrew Powell said tests by Fitzroy River Water, a division of the Rockhampton Regional Council, found that dissolved oxygen levels were between 1.7 and 1.8mg/l.
Mr Powell said the optimal dissolved oxygen level for fish was 5mg/l – below 2mg/l they are not likely to survive.
The state Opposition had called on the Newman government to launch an independent inquiry into whether the release of mine water into the Fitzroy River led to the fish deaths.
Shadow Environment Minister Jackie Trad said reports of dead fish piled along the river were extremely concerning, particularly given the government recently approved the release of mine water into the Fitzroy River.
However, Mr Powell said the low oxygen levels were most likely the result of massive amounts of organic material, which had built up during an extended dry period, being washed into river by the heavy rains.
“The organic material decomposed and consumed oxygen, which made it impossible for fish to survive,” he said.
“We will continue our investigations though, and EHP will liaise with other expert agencies such as the Department of Natural Resources and Management.
“The fact is that this incident, as unfortunate and distressing as it is, is a natural phenomenon which is a result of the natural disaster that hit Queensland last week.
“We have similar reports of fish kills up and down the coast, in Gladstone and the Boyne River, even from the Maroochy River in my region.
“Experts from my department are also conducting comprehensive investigations.”
Mr Powell said that as of Wednesday evening, the water flow past Rockhampton was over 5.5 million megalitres, the equivalent of 11 Sydney harbours.
“Less than 10,000 megalitres of that water was released from mine sites, or 0.18 per cent of the total flow, so we are talking about a drop in the ocean,” he said.
On January 25, Mr Powell confirmed that four coal mines involved in the Fitzroy Basin pilot program had commenced the first controlled release of stored mine water as heavy rain fell across the region.
He said the deluge from ex-tropical cyclone Oswald had provided sufficient stream flow for the BHP Mitsubishi Alliance (BMA) mines – Goonyella Riverside, Peak Downs, Norwich Park and Saraji – to release water into the Fitzroy River system.