This backs up a 2019 study, which found extensive evidence of erosion associated with IVTs in summer.
The University of Melbourne study is the first since 2011 to assess environmental entitlements in the river, which have grown from almost zero gigalitres in 2006 to 360 Gl in 2020.
As part of the project, researchers mapped all water flows in the system and their effects.
The data they ended up recording was far more accurate than the Natural Flows Paradigm method typically used.
Involved in the study was water policy expert Avril Horne, who told community members the project embodied a “different approach” to running an environmental flows study.
The report found water trading between the Goulburn and Murray systems was increasing due to increased plantings in the Murray system and drought conditions in NSW.
Researchers found “significant volumes” of IVT were creating “unseasonal and prolonged high summer flows” downstream of Goulburn Weir.
“Australian river systems have not evolved under conditions of elevated, constant flows and so ecological impacts from IVTs are inevitable,” the report said.
From 1976 to 2010 the average flow at McCoys Bridge in summer was 600 Ml a day.
In the summer of 2019-20, the average flow was 2213 Ml.
Researchers believe the IVT demand on the Goulburn system will only get worse as climate changes continues to affect the Murray-Darling Basin.
They believe the Goulburn system is less vulnerable to climate change compared to nearby rivers and will likely become a popular go-to for consumptive water in the future.
“There is real concern these demands will result in adverse ecological outcomes,” the University of Melbourne report said.
In reaction, the study developed a new flow management tool to help the Goulburn Broken Catchment Management Authority adapt environmental flows to limit damage to the river.
The biggest overall take-home from the Kaiela (Lower Goulburn River) Environmental Flows Study was that the science needed to be constantly updated and revised.
Researchers recommended further studies on the Goulburn system in place of offering any clear solutions to problems identified.
The study was requested by the Goulburn Broken CMA, which highlighted climate change and IVTs as areas of particular concern.
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