WATER authorities released blackwater into the Darling-Baaka River at Menindee just two days before catastrophic fish kills began last month, an independent investigation has found.
The investigation, by volunteer community journalists Megan Williams and Dan Schulz, found that the release contributed to the death of an estimated 20 million fish despite knowledge that the release of blackwater had caused fish kills just a month earlier.
The authors said the blackwater release contributed to the March Menindee fish kills but has not been acknowledged by water authorities.
The investigation compared satellite imagery with on-ground photos for the month leading up to the mass fish kills and showed that blackwater was released from Lake Wetherell.
The authors said that during flood operations, the strategy was to dilute the blackwater through the shallow lakes at Menindee after it had built up through the flood in January.
But when the water was released into Lake Pamamaroo, WaterNSW had not yet closed the Pamamaroo outlet that flows into the Darling-Baaka.
The NSW Department of Planning and Environment (DPE) observed blackwater in Lake Wetherell being drawn through the Pamamaroo outlet and then downstream to the Darling-Baaka in February which led to fish kills that month.
The authors said WaterNSW and DPE had successfully executed a strategy in early March to re-oxygenate the Darling-Baaka by reducing flows from Lake Wetherell, but on March 14, satellite imagery shows both regulators open, and blackwater making its way toward the river.
By the evening of March 16, fish had begun to die again.
The investigators said these actions were never addressed by WaterNSW or the DPE despite weeks of community consultations during the aftermath of the fish kill.
They said their report challenges claims made by WaterNSW that “very limited management actions could have prevented (the March mass fish kills)” in Menindee.
In a community update published on March 21, WaterNSW stated: “The fish deaths are a natural event associated with record flooding in the area. There are very limited management actions that could have been taken to prevent it from happening.”
The authors recommended that the NSW Government’s 2023 Menindee Fish Kill Inquiry include a detailed analysis of releases from all regulators at Menindee Lakes; a review of the timing of discharges from Pamamaroo inlet; a review into why blackwater held in Lake Wetherell was discharging directly into Pamamaroo Creek; and a review of what engineering and/or management solutions were available to water authorities to manage blackwater held in Lake Wetherell.
