Navigable aqueducts (sometimes called navigable water bridges) are bridge structures that carry
navigablewaterwaycanals over other rivers, valleys, railways or roads. They are primarily distinguished by their size, carrying a larger cross-section of water than most water-supply
aqueducts. Roman aqueducts were used to transport water and were created in Ancient Rome. The 662-metre (2,172 ft) long
steelBriare aqueduct carrying the
Canal latéral à la Loire over the River
Loire was built in 1896. It was ranked as the longest navigable aqueduct in the world for more than a century, until the
Magdeburg Water Bridge in Germany took the title in the early 21st century.
Early aqueducts such as the three on the
Canal du Midi had stone or brick arches, the longest span being 18.3 metres (60 ft) on the
Cesse Aqueduct, built in 1690. But, the weight of the construction to support the trough with the clay or other lining to make it waterproof made these structures clumsy. In 1796
Longdon-on-Tern Aqueduct, the first large
cast iron aqueduct was built by
Thomas Telford at
Longdon-on-Tern on the
Shrewsbury Canal. It has a total length of 57 metres (187 ft) across three intermediate piers. Within ten years Telford had completed the far more ambitious
Pontcysyllte Aqueduct in Wales on the
Llangollen Canal over the
River Dee valley, with a total length 307 metres and a height of 38 metres, making it the tallest navigable aqueduct in the world. Other cast-iron aqueducts followed, such as the single-span
Stanley Ferry Aqueduct on the
Calder and Hebble Navigation in 1839, with its innovative 50-metre (160 ft)
through arch design.
There were 32 navigable aqueducts on the
Erie Canal, constructed 1817–1825 in
New York State, United States.
Notable navigable aqueducts
Benjamin Outram's 44 ft long (13 m) single-span Holmes Aqueduct on the
Derby Canal in
Derby was the world's first navigable
cast iron aqueduct, narrowly pre-dating
Thomas Telford's 186 ft long (57 m)
Longdon-on-Tern Aqueduct on the
Shrewsbury Canal, sometimes described as the world's first large-scale navigable cast iron aqueduct. The oldest currently navigable cast-iron aqueduct is Outram's Stakes Aqueduct on the
Huddersfield Narrow Canal at
Stalybridge, built c1801 to replace an original, stone-built, four arch structure, which had been swept away in the floods of August 1799.
Pontcysyllte Aqueduct (307 metres, 1,007 ft) carries the
Llangollen Canal over the River Dee valley in north
Wales; it was designed by
Thomas Telford, opened in 1805 and is the highest navigable aqueduct in the world. The same canal, which includes a tunnelled section, crosses a second valley on the
Chirk Aqueduct (1796–1801). This navigable canal also supplies water to the former borough of
Crewe and Nantwich.
Sir
Arthur Cotton planned the aqueduct at
P. Gannavaram,
Andhra Pradesh in
India to cater for the needs of farmers in the
Konaseema area while he was constructing the
Dowleswaram barrage. Originally a non-navigable aqueduct was constructed in 1859 with a length of 700 metres (2,300 ft). In 2000, a new navigable aqueduct and road bridge was constructed across the
River Vynateya (a tributary of the
Godavari River) near Gannavaram, to facilitate the crossing of the
Gannavaram Canal and also to irrigate a farming land.
Following construction of the
M6 Toll Motorway the building of the
Lichfield Canal Aqueduct ran into construction difficulties. The UK parliament passed legislation preventing a road being built in the path of a canal being renovated without providing a tunnel or aqueduct for canal traffic to pass.
Notes: 1 Contains
canalised river. 2 Partly or mostly navigable, and/or under restoration. 3 A system of canals. Canals which form part of this system are not listed here individually.