The Halifax arm of the Calder and Hebble canal is set for weeks of repair works after a culvert collapsed.
A temporary dam has been installed to stop any more water draining from the canal and so that boats which are moored won’t get damaged falling onto the canal floor.
A hole has been formed in the canal bed and engineers from the Canal and River Trust are currently assessing the damage.
A rescue also had to be carried out on hundreds of fish from the canal, which have now been placed in a safe environment until the repair work is completed.
Stephen Hardy, communications manager for the trust, said: “We hope to begin works shortly but until we’ve finished inspecting the canal we won’t know exactly what needs to be done or how long it will take.
“But we anticipate that it could be around ten or 12 weeks until the repairs are completed.
“Boats are still able to use the main line of the Calder & Hebble although they are being asked to take extra care and do what they can to help us conserve water.”
The main line of the canal is still open but water levels in the area are low.
The Calder and Hebble Navigation runs for 21 miles from the Aire and Calder Navigation at Wakefield to Sowerby Bridge.
It had 27 locks and connects the Aire and Calder Navigation at Wakefield with the Rochdale Canal at Sowerby Bridge and Huddersfield Broad Canal at Cooper Bridge.
The canal was one of the first navigable waterways into the Pennines.