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 Lock
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.
The lock is at the junction of a canalised section of the Aire and Calder Navigation and the river Calder.
The lock is normally left open as the level of the two sections are the same, however when the river is in flood there can be a small difference in height and the lock is then used. If the level of the river rises higher and navigation becomes dangerous the lock gates are locked to prevent navigation until the river level drops.