Goulburn Broken CMA is recommending that planned summer water transfers to meet downstream demand are delivered as a series of pulses through the lower Goulburn River, rather than a steady flow, to help minimise damage to the river bank.
From December 14 flow in the lower Goulburn river (below Goulburn Weir) is expected to increase from the recommended 800ML/day to up to 3000ML/day to meet downstream (Murray River) water demands from towns, irrigators and the environment. Higher flows of between 2000ML/day to 3000ML/day could continue well in to 2019 if conditions remain dry and demand remains high.
“We share the community’s concern that high unseasonal flows could damage the bank-stabilising vegetation that had started to re-establish and spread thanks to previous environmental flows,” Goulburn-Broken CMA CEO Chris Norman said.
Since river regulation, winter and spring flows have been captured and stored in dams such as Eildon and then released during peak demand periods in the warmer months. This means rivers now generally flow higher in summer than they would have under natural conditions. Water for the environment is generally delivered at variable rates between autumn and spring to mimic the more natural flows that would have occurred before flows were captured, stored and diverted via dams, weirs and channels.
Modelling shows that this year, if the water hadn’t been stored and diverted, Goulburn River flows of more than 20,000 ML/day (around Shepparton’s minor flood level) would have occurred in August and September after rain in parts of the upper catchment (above Eildon).
“After seeing the impacts of the high unseasonal flows delivered in summer and early autumn this year, we have worked closely with river operators to ensure that whenever possible, future water transfers in summer and early autumn are delivered as a series of pulses, as this is better for river bank health than a steady flow,” Mr Norman said. “This will be particularly important if there are high volumes of water to be transferred over an extended period of time.”
Flows in the Goulburn River between Eildon and Goulburn Weir may be increased to meet the downstream demand. Hydroelectricity generation may also affect river heights in this section of the river.
Mr Norman said that Goulburn Broken CMA would continue to monitor bank vegetation at various sites along the lower Goulburn River to measure the impacts of high unseasonal flows.
“We are continuing to meet with key agencies to look at ways we can minimise the environmental effects of high unseasonal flows due to water transfers,” Mr Norman said.
“We know that the Goulburn River is the lifeblood of this region, providing numerous economic, recreational and environmental benefits, which is why we will continue to keep the community in the loop about how the river is being run and why they are seeing these changes in river height and flow.”