Environmental water is a sore spot in river communities, described as both the best and worst thing to happen to the Murray-Darling Basin — depending on who you ask.
Commonwealth Environmental Water Office assistant secretary Hilary Johnson addressed bank erosion in the Q&A, using the Goulburn River as an example of how the science has improved.
“Erosion is a growing issue and it is a natural process we’ve seen increase quite dramatically,” Mr Johnson said.
“One of the key things we’ve found is that long, stable flows result in bank notching, particularly over summer, and when a higher flow comes in later that bank material above the notch slumps.”
Mr Johnson said environmental water was now used as a buffer, running in after high flow events so the water level dropped slowly and bank material didn’t slump over notches as dramatically.
“We also try to improve that variability (in water level) ... we try and do things to promote the growth of vegetation along the river banks which we’ve had success in places like the Goulburn River,” he said.
“Also our ability to get water out of the main river channel and into floodplains, creeks and flood runners that go around the main channels help us to dissipate that flow power compared to, say, concentrating it through a pipe.
“It reduces the energy and hopefully reduces erosion.”
Mr Johnson said the CEWO’s ability to dissipate flow power was currently limited by height and volume rules.
The CEWO manages $4 billion worth of water across the basin — not including entitlements it jointly owns with other water bodies.
“It’s really important we have close collaboration with communities, First Nations and scientists,” Mr Johnson said.
“The foundation of our planning is robust, scientific observations ... and communities are our eyes and ears on the ground.”
The CEWO runs several regional advisory groups which supply the majority of its “eyes and ears on the ground”.
MDBA environmental management senior director Janet Pritchard said water for the environment became crucial when more than 50 per cent of flows started to be diverted.
“As we began using over 50 per cent those issues of salinity, algae booms, acid sulphate soils and bank erosion happened — then the millennium drought occurred,” Ms Pritchard said.
“Environmental water is used to enhance the natural peak flows in the basin, allowing the pulses to reach higher and last longer.”
Ms Pitchard said environmental flows also helped other water users as they increased connectivity throughout the system, allowing easier water delivery.
“If we didn’t have environmental water, the emergency drought framework would have been triggered in South Australia several times by now,” she said.
“We know the climate is getting hotter and drier, we need to work together better. Not just government — government needs to work with communities.”
According to the experts in government, getting better at sharing knowledge and engaging with locals is key to creating a better future for the basin.
The full webinar session can be viewed at: mdba.gov.au/webinars
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