SA waterway health project benefits local environment and agriculture

Posted 2 August 2017

WeirA project manipulating weir pool levels to improve waterway health in South Australia’s Murray River has won the Australian Water Association Environmental Improvement Award at the 2017 Water Industry Alliance Smart Water Awards.

South Australia’s Department of Environment, Water and Natural Resources (DEWNR) weir manipulation project was set to improve the Murray River environment. 

Environmental Pathways Manager Tumi Bjornsson said the project assessed environmental impacts of weir pools on the river by determining how varied water levels affect the river’s health.

“The natural water level and flow of South Australia’s River Murray is seasonally variable, but in the 1920s lock and weir structures were built to support development and regulate the flow,” Bjornsson said.

“Over the years, the structures have reduced the river’s seasonal variability and negatively impacted its ecosystems. The weir pool project is about changing the management of the existing locks and weirs in order to reintroduce some of the variability.”

An important element of the project involved assessing how weir pool changes impact landowners, Bjornsson said. 

“We did a lot of work to identify impacts to landowners in the area, but also assessed the potential benefits. The project was really about documenting all of those things and making sure the information was at hand for those making the decisions about whether we change the levels in any given year,” Bjornsson said. 

Weir Pool Manipulation Project Manager Jaimi Smith said testing variable water levels resulted in some positive outcomes in soil salinity levels and vegetation. 

“We were freshening the soil about 30-50m around the water's edge, which has seen improvements in floodplain vegetation. The vegetation that was watered by the weir pool raising stayed healthier for longer throughout the dry summer period,” Smith said. 

“When monitoring the bottom of the river’s food web, we saw a positive response in biofilm. It temporarily changed from an algae base to a bacteria base – essentially a better food source for macroinvertebrates and fish. This builds up through the food chain to birds and larger fish and frogs.”

Aside from testing the environmental impacts of variable water levels, Smith said the project is also about testing the process for an ongoing program. 

“We are looking into how weir pool manipulation can become a normal part of Murray River operations,” Smith said.

“The project was also an opportunity to road-test government processes and community support. A huge part of it was not just the ecological response, but also community and government acceptance.”

Take a look at all the 2017 WIA Smart Water Award winners here. If you have research, a project or innovation making a difference to the South Australian water industry, enter into the Australian Water Association's South Australian Water Awards here. Submissions close 18 September.