Goulburn Broken Catchment Management Authority environmental water and wetlands manager Simon Casanelia said the water was being monitored and that there was no cause for alarm.
“When high levels of organic material wash into a waterway it can reduce dissolved oxygen levels, particularly when the weather is warm,” Mr Casanelia said.
“If dissolved oxygen levels fall too low, fish and other aquatic animals can die.”
He said platypuses and turtles were not reliant on dissolved oxygen in the water to survive.
According the the GBCMA website, dissolved oxygen levels typically range between five and 14 mg/L (or ppm).
Low-oxygen conditions occur when water has become low in dissolved oxygen, typically less than 4mg/L, for an extended time.
Levels at less than 2mg/L are considered ‘critical’ and may cause fish to die.
“Monitoring has indicated dissolved oxygen levels have remained suitable for fish and other aquatic animals,” Mr Casanelia said.
“No impacts on aquatic fauna have been identified.”
Mr Casanelia said it was hard to say how long it would take for the water to clear, but that flow in the Goulburn River was currently increasing due to the delivery of environmental water, which would help dilute the poor-quality water and maintain dissolved oxygen levels.
While some fisherfolk in the Goulburn Valley have reported “bad fishing” on local social media pages, Mr Casanelia said the environmental event might actually improve conditions for the sport.
“These events are a natural occurrence,” he said.
“Increased organic loads can help improve instream productivity and therefore increase food resources for native fish and other native fauna.”
With rainfall likely increasing closer to winter, Mr Casanelia said it was possible there would be more occurrences of darkened water in the system connected to waterways within the fire zone.
Goulburn Valley Water general manager service delivery Daniel Flanagan said the utility was monitoring the situation.
“The recent fires and rain that followed has impacted the quality of raw water supplies across Goulburn Valley Water’s service area. This includes the Goulburn River,” he said.
“This can make drinking water treatment more challenging.
“We are carefully monitoring water quality parameters, including those related to larger organic matter loads, and adjusting our water treatment processes to ensure we continue to meet Australian Drinking Water Standards.”
