A three-month project to update the 240-year-old listed Dowley Gap aqueduct has finished.

Temporary dams were installed at both ends of the aqueduct, in Bingley, to hold back the water and a 250-metre section was drained so leaks could be repaired in time for the boating season.

The neighbouring two rise lock flight at Dowley Gap had two new sets of 3.5 tonne lock gates installed.

The gates are tremendously strong as they have to control huge water pressures, take the hard usage they get from the thousands of boats which pass through each year and survive for at least 25 to 30 years underwater.

The locks and aqueduct were built around 1773 on the Leeds-Liverpool Canal and are listed as Grade II* for their architectural and historic interest and association with the Three and Five Rise Locks.

Project manager for the Canal & River Trust Paul Brown said: “Significant canal leakage was detected through the north east and south wing walls and on the underside of the east side during our routine inspections. Due to the severity of the leakage, we had to undertake this major project to prevent further deterioration of this important heritage landmark.

“Our winter maintenance period is one of our busiest times of year and is essential work to make sure the canals and rivers are kept in the best possible condition. There’s been a variety of works carried out including the leakage reduction works, hundreds of fish were relocated during one of our fish rescue, as well as the lock gate replacements.”

The work comes is part of the charity’s £50m investment on conservation and maintenance works across 2,000 miles of waterways in England and Wales.

Mr Brown said: “We were able to incorporate a really successful open day where more than 2,000 people were able to take a behind-the-scenes tour of these canal structures.

“It was the first time we’d done this at one of our aqueducts and there was great public interest in the works. It’s really satisfying as it shows that there is great community support out there for our waterways which is vital to their long-term protection.”

Nick Sharp, project manager for engineering contractor May Gurney, added: “Few people realise that many canal locks, buildings and structures are listed monuments and that the waterway network is one of the finest living references to Britain’s industrial revolution.

“As a result, we are incredibly proud to play our part in the Trust’s work to preserve the canals and rivers of England and Wales.”