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The Aire and Calder Navigation consists of a number of discrete sections of canalised river, which enable boats of a reasonable size to reach Leeds. It was developed gradually from 1699 until the mid-19th century, with the involvement of many famous civil engineers such as John Smeaton, John Rennie, Thomas Telford and George Leather. Locks were being enlarged right up to the 1960s. The original intention was to give Leeds a proper ship canal capable of taking seagoing vessels, like Manchester's, but that never happened. However it is capable of taking boats up to 200ft long, 20ft wide and with 8ft draught - considerably larger than most English canals.

Unlike narrow canals it didn't see the complete abandonment of commercial use in the late 20th century: parts of it were used regularly for delivering coal to Ferrybridge Power Station until the early years of the 21st century and there is still a modest amount of commercial traffic. The coal traffic used a unique system of trains of small 'tubs' towed by a tug.

The extant sections in the Aire valley are 7.6km parallel to the river Aire between Knowsthorpe (Knostrop) and just below Woodlesford, 1.1km downstream of the confluence of the Aire and Calder at Castleford, and the longest section, c.30 km from Ferrybridge down to Goole Docks, originally called the Knottingley and Goole Canal, where it joins the Ouse downstream of its confluence with the Aire. There is also a 13km branch up the lower Calder valley from Castleford to near Wakefield, where it joins the Calder and Hebble Navigation.

Sources consulted include 'Civil Engineering Heritage: Northern England' (M.F.Barbey, 1981) and the Canal and River Trust website Link

The River Calder is a river in West Yorkshire.
The Calder rises on the eastern slopes of the Pennines flows through alternating countryside, former woollen-mill villages, and large and small towns before joining the River Aire near Castleford, 45 miles later.
The river's valley is generally known as the Calder Valley. The name Calderdale usually refers to the large urban and rural borough (centred on Halifax) through which the upper river flows. The lower reaches flow through the boroughs of Kirklees (based on Huddersfield) and Wakefield. However, the river does not flow through the centres of Halifax and Huddersfield, which are on the Calder's main tributaries, the River Hebble and River Colne respectively. The only large town centres through which the Calder flows are Brighouse, Mirfield, Dewsbury and Wakefield.