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Winter environmental flow good for plants, water quality and migratory fish

Friday 8 June, 2018
Upper bank vegetation and water quality will benefit from an environmental flow along the lower Goulburn River planned for mid-June, with the benefits expected to extend all the way to South Australia’s Coorong.

Water for the increased flow is due to be released from Goulburn Weir from Wednesday June 20, peaking at about 9,500 ML/day (4.30m) at Murchison on Thursday June 28. The increase in river flow and height is well below minor flood level (9m at Murchison and 9.5m at Shepparton). In the event of heavy rain, the timing and size of the environmental flow could change or not go ahead at all. 

“As much of the rain and run-off into the Goulburn River is now captured in the dams and used to supply towns, industry and farms, the amount of water flowing down the river in winter and spring has reduced,” Goulburn Broken CMA Environmental Water Manager Simon Casanelia said.

“It also means the river flows higher and faster in the hotter months of the year when communities require more water, which is the opposite of what would happen if there were no dams and weirs. These changes have affected the health and survival of native plants and animals, so we’re giving nature a helping hand and delivering environmental water at this time of the year to mimic more natural flow conditions.”

Mr Casanelia said as flows along the lower Goulburn River had been running higher than usual for the past five months to meet the increased Murray River irrigator, community and environmental demand, this year’s winter flow had been designed to decrease at a slower rate than flows delivered at the same time of year in the past. The slower rate is designed to reduce the risk of riverbank slumping or erosion.

“This year’s flow is targeting bank vegetation higher up the banks, rather than the lower bank vegetation which has been inundated for quite some time now,” Mr Casanelia said. “Water bugs and fish will also benefit.”

The environmental flow will take about a week to reach the Murray River and will provide multiple downstream benefits, including supplying water to wetlands along the Murray River and triggering upstream migration and spawning of pouched lamprey, a rare and primitive eel-like fish that enters the Murray system via South Australia’s Coorong estuary.

Pouched lamprey move between saltwater and freshwater to complete their lifecycle, migrate from the sea and travel large distances upriver to spawn. After a similar environmental water release from the Goulburn River made its way down the Murray in 2015, a pouched lamprey that was tagged with a microchip at the Coorong estuary was tracked all the way to Lock 11 (near Mildura); a journey of almost 900 km. 

Mr Casanelia said co-ordination of the delivery of the environmental flow highlighted the types of activities the Tri-State NRM Murray Alliance – a group of natural resource management agencies from Victoria, NSW and South Australia who are working together to improve environmental, social and economic outcomes along the entire Murray River Corridor – could achieve.

Department for Environment and Water (SA) Icon Site Coordinator for the Lower Lakes and Coorong Adrienne Rumbelow agreed.

“Fishway construction on River Murray locks and barrages has improved migration and breeding opportunities for many native fish species like the pouched lamprey,” Ms Rumbelow said.

“The co-ordinated delivery of environmental water plays an important role by providing the flow triggers to encourage fish movement, while providing ecological benefits along the Murray River. This is a great example of co-ordination between states, the Murray-Darling Basin Authority and the Commonwealth Environmental Water Office to achieve multiple environmental outcomes along the river.”

Environmental flows are planned by the Goulburn Broken CMA in consultation with the Commonwealth Environmental Water Office and the Victorian Environmental Water Holder (VEWH). The delivery is managed by Goulburn-Murray Water in line with the VEWH’s Seasonal Watering Plan 2017-18. Timing of the environmental flows take into consideration delivery orders by irrigators and other water users and feedback from the community via the Goulburn Broken CMA’s environmental water advisory groups.

Environmental watering is only one way of protecting and improving rivers and wetlands. Fencing and revegetation, erosion control, pest control, returning logs to rivers for fish and bug habitat, and installation of fishways to allow fish to pass through dams and weirs also help. Find out more about these activities here.

 

Pouched lamprey - Department of Environment and Water (SA)