A specially designed amphibious vehicle from Australian Aquatic Services was used to help move azolla along the lower Broken Creek downstream of Nathalia to improve flows for irrigators and native fish last week.
Goulburn Broken CMA Environmental Water Co-ordinator Daniel Lovell said azolla was a naturally occurring water plant that grew quickly in slow-moving water within the creek.
“Managing azolla is one of the key objectives for our environmental watering actions in the lower Broken Creek because it can cause water quality issues,” Mr Lovell said.
“The water quality risk increases in late spring/early summer when the azolla starts to die. As it breaks down it removes oxygen from the water, which can lower the oxygen levels, that in turn can affect native fish and aquatic animals.”
Each year Goulburn Broken CMA works with Goulburn Murray Water (GMW) and the environmental water holders to use environmental water deliveries to increase flows with the aim of breaking up and flushing the azolla out of the creek. Dissolved oxygen levels are also monitored. Delivery and system constraints mean that GMW can’t always provide sufficient flows to break up and mobilise the azolla.
“This year the azolla growth has been so vigorous that while the flow deliveries mobilised and controlled the azolla in most of the creek, there were some sections where big carpets of azolla blocked the creek near Hardings, Luckes and Schiers weirs,” Mr Lovell said.
“Last week we engaged Australian Aquatic Services with their weed removal equipment to physically break up and shift the azolla in the creek. This was done in conjunction with increased environmental and operational water deliveries into the creek.
“The risk has been reduced but we will continue to monitor the situation and maintain flow so native fish can more easily move and seek refuge from any areas that remain affected by azolla.”