Residents have been told it could take a number of years to see a ‘real impact’ after efforts to keep weeds under control at Sankey Valley Canal were ramped up.
Warrington Borough Council is assuring anglers, residents and visitors that it is doing all it can to address the issue.
Problems are being caused by a range of aquatic plants.
Some species remain submerged, hornwort, some are rooted in the canal bed but with leaves that emerge through the surface, water lily, and other plants float on the surface, azolla and duckweed.
These plants can cause oxygen levels to drop during the night, which can have an impact on fish.
The council has developed a water management plan to address the issues, in partnership with the Environment Agency and the Dallam and District Community Angling Club.
However, it has stressed that it may take a ‘number of years’ before people begin to see a ‘real impact’.
Cllr Tony Higgins, cabinet member for leisure and community, said green weeds and plants in Sankey Valley Canal present a ‘number of complex challenges’.
He added: “These are not are not easily overcome, as when we successfully remove one type of weed, it provides opportunities for others to flourish.
“They take advantage of this and reproduce rapidly.
“We know that these are unsightly and can impact on fish stocks, and we are listening to the concerns of people.
“Together, we are doing all we can to manage water plants on and in the canal to improve the look and appeal, benefit wildlife and improve angling. But it will take time.”
The council says a major challenge at the canal, currently, is the rapid growth of a number of species of water lily.
This plant, although beneficial to wildlife in small quantities, has developed significantly in recent years.
Physical removal is said to be very difficult as the plant regenerates with ‘increased vigour’ from any small root pieces not removed.
The council will be spot treating a number of the plants this year with a herbicide, under licence from the Environment Agency, to reduce the coverage, with the aim of creating a central channel of lily-free water between Sankey Way and Callands Pool.