This was the finding from modelling carried out as part of a constraints feasibility study to see what environmental effects would be created by loosening river operating rules along the Goulburn River and portions of the Murray River.
“Despite the technical work for this feasibility study demonstrating the significance of relaxing constraints in the Goulburn to enhance flows in the Murray River, the modelling completed by the MDBA suggests relaxing constraints has minimal impact on higher flow levels at the South Australian border,’’ it was reported in the feasibility study.
However, the report of the consultative committee found that further investigations were warranted into the benefits, risks and costs of relaxing constraints to enable over-bank flows up to minor flood level on the Goulburn and Murray rivers.
They strongly advised that key elements of the feasibility study should be discussed with the community before a preferred relaxation option is adopted by government and discussions are held with all affected landholders.
Most committee members recommend that relaxed constraints should only be used to provide greater flexibility to deliver already available water for the environment.
Pushing river levels to over-bank flows could affect roads, bridges, private land, infrastructure, stock, crops, pumps and people.
The committee report recommendations mean that a detailed business case will be developed for the constraints project.
A dissenting member of the committee, Jan Beer from Yea, argues that investigations by Victorian Water Minister Harriet Shing’s own department shows constraint relaxation is neither feasible nor technically achievable with no beneficial impacts from relaxation of constraints beyond Torrumbarry due to attenuation and evaporation.
“Modelling as undertaken by the Murray Darling Basin Authority, Department of Energy, Environment and Climate Action and University of Melbourne for hydrological outcomes of the feasibility study clearly stated, ‘The observed difference between the current and relaxed constraint scenarios ... decreases downstream of Torrumbarry and the Wakool Junction’,” Ms Beer said.
“This reduction at the higher flow levels reflects the geographical nature of the mid-Murray section and the Edward-Wakool section where water needs to travel through the flat and wide landscapes once water goes beyond in-channel pathways. Therefore, the peak of events is largely attenuated by the time it reaches to Wakool Junction,” the report said.
Ms Beer said the constraints management strategy developed by the Murray-Darling Basin Authority was created to deliver greater volumes of environmental water downstream, with the aspiration assumption of achieving “enhanced environmental outcomes” predominantly in the lower Murray and South Australia.
If those objectives can’t be achieved, then she contends that it is morally reprehensible to proceed with the project and a waste of billions of dollars of taxpayers’ money if the extra 450 Gl of environmental water cannot be delivered down the rivers.
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