The fish kill occurred on December 15, 2018 and a further larger kill on January 6, 2019.
The report identified a number of factors that contributed to the fish kills including:
- High temperatures and low or no flow conditions that led to thermal stratification.
- Rainfall on 15 December 2018 and a drop in temperature appears to have mixed water layers and potentially disrupted surface algal blooms, which contributed to very low oxygen throughout the water column.
- Substantial drops in daily temperatures from 46 degrees to 28 degrees on 4 and 5 January 2019 and associated cold fronts passing through the region caused layers of water with different dissolved oxygen levels to mix, reducing the overall dissolved oxygen available.
- High algal content in stock and domestic flow releases drawn from Lake Pamamaroo, which increased oxygen demand and consumption, further reduced dissolved oxygen available to fish.
Investigations also found numerous fish deaths occurred in the Lower Darling River and Menindee Lakes between 2002 and 2004 during the millennium drought.
NSW Cross Border Commissioner James McTavish has been appointed as Regional Town Water Supply Co-ordinator. In his role, he will oversee the work already done to ensure water supply and quality in towns and communities all over NSW.
Deputy Premier and Minister for Regional NSW, John Barilaro said the fish kill was unprecedented and a major ecological disaster.
“We know there is anger and frustration following this incident but we are working hard to support Far West communities with practical measures,” Mr Barilaro said.
“We’ve brought in six aerators which may provide small areas of fish refuge in the hope we can mitigate any further devastation to the ecosystem but we accept that this is not a silver bullet.”
Minister for Primary Industries Niall Blair said the interim report allows the NSW Government to look at the best available science to protect and recover native fish populations when conditions eventually improve.
“We understand how devastating this event has been on the community of Menindee and Broken Hill and we are doing everything we can to assist now and prepare for potential further kills this month,” Mr Blair said.
“I want to work with other states and federal agencies to deliver improved management for protecting and enhancing our native fish populations in the Murray-Darling Basin including better water quality and fish monitoring, increased restocking and improving fish passages to allow fish to move, feed and breed.”