Submerged weeds affect water flow, promote silting and cause issues with automatic regulators, which can reduce G-MW’s ability to deliver water to its customers.
The irrigation shutdown period between May and August provides a significant opportunity for treating weeds.
G-MW environmental maintenance coordinator Dannielle McMillan said the weed treatment program during this irrigation shutdown was the most ambitious the water authority had ever undertaken.
“Last year was a landmark year for us in terms of weed treatment,” she said.
“After successful trials using a herbicide with very low toxicity to fish life, we were able to treat more than 230km of channel for aquatic weeds such as hornwort, saggitaria, ribbon weed and egeria.
“Last irrigation season, we saw the benefits of this, with flow rates improving in many of the channels we had treated.
“We are subsequently looking to undertake an even more extensive weed treatment program this year, with about 300km of channel identified for treatment.”
About 100km of channel have already been treated as part of the 2023 program.
Typically, aquatic weeds are treated by a section of channel being dewatered and the weeds being directly sprayed with herbicide, however in sections of channel that are difficult to access, G-MW has begun treating weeds by flowing injection.
This involves the herbicide being dispersed from a regulator where it can then flow downstream and spread across the treatment zone.
For more information on G-MW’s weed treatment program, including an interactive map showing which sections of channel are being treated, visit: www.g-mwater.com.au/winter-works
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