In recent years, G-MW has expanded its weed treatment program from treating about five kilometres of channel annually to treating more than 200km each year.
G-MW environmental maintenance coordinator Dannielle McMillan said this was due to a series of improvements the authority had either driven or assisted.
“We have been working closely with suppliers to learn of any new, environmentally friendly herbicides on the market, and of any ways we can support their development,” she said.
“There were no herbicides for treating aquatic weeds that were cost-effective and safe for native fish and other wildlife, but in the last three or four years this has changed.
“In addition to helping suppliers develop new herbicides that support our needs, we have tested several application methods for this herbicide.”
In 2022, G-MW trialled treating a channel west of Cobram via flowing injection. Rather than dewatering the channel to treat it, this saw the herbicide gradually dispersed into a channel near a regulator, with flows then carrying the herbicide down the channel.
This year, G-MW is continuing to trial using drones to treat weeds in locations that would otherwise be difficult to access.
“We have taken a data-driven approach to both identifying which channels we need to treat and the efficacy of our treatment,” Ms McMillan said.
“Because the program has expanded so significantly in recent years, we have been able to collect a lot more data, and what it has shown has been really positive.
“We can see that flow rates in the channels we have treated with new herbicides have improved substantially, and we can also see the different methods we have been using to disperse the herbicide has been effective.”
By the end of its 2024 Winter Works Program, G-MW will have treated about 10 per cent of its 6000km channel network in just three years.
Prior to the improved weed treatment program that began in 2022, achieving this coverage would have taken about 120 years.
“In between irrigation seasons, we can dewater channels and apply the herbicide directly to weeds, which remains the most effective method,” Ms McMillan said.
“We also know in certain areas, simply dewatering channels and exposing the weeds to frost can help kill them even when no herbicide is involved.”
The herbicides G-MW uses have very low toxicity to humans and mammals. G-MW says no fish deaths have been recorded since it started being used in 2021.
For more information, go to: https://www.g-mwater.com.au/weed-treatment-2024
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