The recent increase in the height of the Goulburn River downstream of Murchison was due to run-off and inflows from tributaries including the Broken River and Seven and Pranjip creeks, Goulburn Broken Catchment Management Authority (CMA) Environmental Water Co-ordinator Daniel Lovell said.
“With more than 100mm of rainfall recorded in many parts of the catchment in the past few weeks we’re now seeing increased run-off into creeks, with many previously dry waterways starting to flow for the first time in almost a year,” Mr Lovell said.
“The extra water from these tributaries flows in to the Goulburn River and ‘tops up’ the environmental base flow of 500ML/day that is being released from Goulburn Weir to the lower Goulburn River. In fact, overnight on July 14, the Goulburn River at Shepparton peaked at almost 8000ML/day – a river height of just over 5m – with most of this water coming from Broken River flows.”
The minor flood level at Shepparton is 9m.
A base flow of 500ML/day is released from Goulburn Weir year-round to maintain water quality and provide shelter for native fish, water bugs and other animals in the lower Goulburn River.
“Without this base flow, in dry years such as the one we’ve just experienced, the lower Goulburn River, and the plants and animals that rely on it, would be quite stressed,” Mr Lovell said.
“For the past few years, we’ve also delivered additional water in spring and autumn to try and mimic the more natural flow patterns that would have occurred before dams, weirs and channels altered the river’s flows. These flows have resulted in significant re-growth of river bank vegetation that prevents erosion and provides critical habitat for small fish and bugs.”
Last year’s October (spring) flow peaked at 7500ML/day (river height at Shepparton of 4.96m) while the March (autumn) flow peaked at 4500ML/day (river height 3.93m at Shepparton). The main aim of the flows was to improve and extend bank-stabilising vegetation along the river. The extra water also provided recreational benefits such as improved fishing and boating. Wherever possible, environmental water deliveries are timed to piggy back on deliveries of water to irrigators and other users. The water is also “re-used” at wetlands such as Gunbower and Hattah as it makes its way along the Murray River.
Information about proposed environmental water activities in the lower Goulburn River for the next 12 months is available here.