The green menace of river weed has returned to the surface River Witham in Boston again this year – with the thick vegetation causing problems to those using the waterway.
Weed boats have been deployed to clear some of it, but the Canal and River Trust (CRT) says it has become a ‘perennial problem’.
The blanket weed has now lead to sports and recreational activities to be cancelled – with some boaters saying the river is ‘impassable’.
Boston Rowing Club has issued a statement to say they have had to cancel their annual ‘marathon’ event.
They said: “The decision is entirely due to the weed in the river.”
Describing the weed as ‘solid’, they went on: “This is entirely beyond our control and we are in long-term and ongoing dialogue with the CRT as the management of the river is not acceptable.”
A spokesperson for the club added via Facebook: “Such a shame that for the past two years the river has been allowed to get in such a state.
“Not just bad for leisure use and the businesses along the river but ecologically has a huge effect to fish.”
The green layer is said to be a combination of duckweed, which multiplies in hot weather, and an invasive plant species called azolla.
Some boaters who use the river say the weed ‘stinks’ – with one member of Boston Bluetits open water swimmers capturing a photo of pigeons and seagulls walking on top of it.
A spokesperson from the Canal & River Trust said: “We’re really sorry that boaters are being affected by the invasive growth of duckweed on the Witham and we share their frustrations.
"As the charity which looks after navigation on the river, it is a perennial battle at this time of year as low river flows, warm weather and nutrient rich water provide ideal growing conditions for fast-growing invasive and non-native invasive weed.
"Our team is out four days a week clearing tonnes of weed to help alleviate the situation and we are also working with the Environment Agency to help with the flow of water through Boston to ensure there isn’t a build-up of weed.
“The scale of the problem in recent years has been a real challenge and the reality is that we can’t resolve the situation ourselves. We are the navigation authority for the River Witham but a much wider partnership approach is needed across the river catchment to limit the amount of weed coming onto the river from feeder channels and to increase the amount of weed that is flushed out to sea. “We have some agreements in place which we believe will improve the situation next year and will be trying to encourage dialogue amongst all the partners that can help to tackle the issue.”
A spokesperson for the Environment Agency (EA) said: “We are providing advice in terms of flood risk and water level management with our partners the CRT regarding the River Witham at Boston. “River flows in Lincolnshire are currently low as the county is in a period of drought. Low river flows can contribute to algal blooms.”