Winter flows running through the Murray and Goulburn rivers are giving South Australian water systems a free fill of water, a water lobby group believes.
Good winter rain has raised river levels over the past few months, pushing water into the main river systems and sending water into South Australia's thirsty Lower Lakes.
The Murray-Darling Basin Authority endeavours to have the Lower Lakes filled with fresh water.
Northern Victorian Irrigation Communities president Dudley Bryant said the rain had given the Lower Murray hundreds of gigalitres of free water that is not accounted for as environmental flows.
He believes if the water could have been captured by new dams or better storage management, Murray system irrigators could have increased allocation of up to 35 per cent.
Mr Bryant said 136 Gl of water flowed past Yarrawonga in the Murray in June and 182 Gl in July.
On the Goulburn, in June 150 Gl flowed past McCoy's Bridge and 165 Gl in July.
“That water all goes down the Murray to the Lower Lakes in South Australia and out through the Barges to the sea,” Mr Bryant said.
He said most of the water was generated from tributaries of the Goulburn and Murray as practically zero was being released from the Hume and Eildon reservoirs, apart from a small allocation for power generation.
Because the Waranga Basin reservoir was already full (92 per cent in July), run-off was filling the Goulburn River.
Mr Bryant pointed out the run-off generating the extra flows was not coming out of the environmental allocations.
“South Australia will benefit from the extra flows but it will not come out of their entitlements.”
Based on estimates provided by an engineer, Mr Bryant s calculated that the extra flow could have generated an increase in Murray system allocations, for irrgators, of up to 35 per cent.
He said the extra flows in just a couple of months were above the 450 Gl that were being demanded under the Murray-Darling Basin Plan for extra environmental flows.
The Murray-Darling Basin Authority acknowledges the higher environmental flows achieved by natural rain events.
“This has already been the case in June 2020, where recent wet conditions delivered higher flows in the lower Goulburn reaching 8500 Ml/day and
continue to maintain base flows above the minimum level,” the authority noted in an operations report recently.
NVIC supports the building of ‘Big Buffalo’, an expansion of the Lake Buffalo reservoir in north-east Victoria.