New machines are dredging and cutting back weeds on the Union Canal between Falkirk and Edinburgh at the start of a determined effort by Scottish Canals to tackle the problem.
The Scottish Government-funded body, which launched the project this month, plans to dredge 3,500 tonnes by next March compared to 2,000 tonnes last year.
However, canal users said they remained to be convinced the targets would be met after Scottish Canals scaled back plans in 2013 to dredge 4,000 tonnes a year, because of funding cuts.
They contrasted that with £1 million being announced this month to revamp the Falkirk Wheel visitor attraction.
Ronnie Rusack, chairman of the Lowland Canals Volunteer Group, which also covers the neighbouring Forth & Clyde Canal, said the Union should be 5ft deep but was now only 2ft deep in the middle and inches deep at the sides.
He said: “Boats can hardly pass each other, they cannot manoeuvre, and can’t reach the bank if they get into trouble.”
Pat Bowie, general manager of Re-Union Canal Boats, said: “Over the years it has got worse and worse. If you cannot get on top of the dredging, the canal is going to come to a standstill.”
Scottish Canals said it was confident of making progress after buying £271,000 of equipment and taking over the job from contractors to save £50,000 a year.
Chief executive Steve Dunlop said: “We have not been able to do as much dredging as we would have liked in recent years and know certain locations pose navigational problems for full-draft boats.
“However, we’re dealing with 70 years of silt build-up and it will take major investment of many millions of pounds to completely clear the entire length of the Lowland canals for full-depth vessels.
We’re confident boaters will see an improvement in the navigational channels over the coming year.”
Transport minister Derek Mackay said: “This work will help ensure the safe navigation of the Lowland canals by leisure craft while enabling progress towards the Scottish Government’s aspiration of growth in the numbers of boats navigating these vital tourism assets.”