The Aire and Calder Navigation is a river and canal system of the River Aire and the River Calder in the metropolitan county of West Yorkshire, England. The first improvements to the rivers above Knottingley were completed in 1704 when the Aire was made navigable to Leeds and the Calder to Wakefield, by the construction of 16 locks. Lock sizes were increased several times, as was the depth of water, to enable larger boats to use the system.
Steam tugs were introduced in 1831. In the 1860s, compartment boats were introduced, later called Tom Puddings, from which coal was unloaded into ships by large hydraulic hoists. This system enabled the canal to carry at its peak more than 1.5 million tons of coal per year, and was not abandoned until 1986. To handle trains of compartments, many of the locks were lengthened to 450 feet (140 m).
Although much of the upper reaches are now designated as leisure routes, there is still significant commercial traffic on the navigation. 300,000 tons were carried in 2007, although most of the traffic is now petroleum and gravel, rather than the coal which kept the navigation profitable for 150 years.
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The majority of canals in the UK are true, man made canals, not based on existing rivers. The locks on such canals vary in size, but rarely if ever match the size of the locks on this navigation.
On this section of the Navigation between Leeds and Castleford the locks are just over 200 feet long. This is to conform to the 700 tonne Euro barge standard size of 200 feet by 20 feet.
Because of the size of the locks the lock gates are mechanically operated. For commercial traffic this is always done by a lock keeper that uses an observation tower next to the lock. However leisure boat users are allowed to operate the lock via a control panel on the canal side.
A traffic light system indicates whether leisure boaters can operate the lock themselves. An amber light indicates that there is no lock keeper present and the lock can be self-operated by boaters. This is the normal practice these days except when commercial traffic is expected. If there is a green light showing a lock keeper is present and the lock is ready for you to enter. A red light indicates that the lock keeper does not want you to enter the lock because a commercial craft is being handled.
This lock is much deeper than the others on the navigation because it is a modern lock that replaced two others. It had to be built because in 1988 a section of the navigation subsided into a coal mine which was flooded to a depth of 230 feet.
An act of Parliament was obtained to allow 1.9 miles (3.1 km) of new waterway to be constructed. The original locks at Kippax and Lemonroyd were replaced by this single lock.
On many locks there are warning signs about making sure the boat does not get caught on the cill. It's not always obvious what this means, but basically the wooden lock top gates do not go to the bottom of the lock but sit on a stone base. When the lock is full and a boat is going down, the cill is not visible. This means that when the water is released from the lock it is possible for the boat to get caught on the cill.
When the lock is empty it is much easier to understand how this works. When I took the pictures of this lock the top chamber was empty and the cill was visible.