The River Thames ( ) is a river that flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom, after the River Severn. While it is best known for flowing through :London, the river also flows alongside other towns and cities, including Oxford, Reading, Henley-on-Thames and Windsor.
The river gives its name to three informal areas: the Thames Valley, a region of England around the river between Oxford and west London; the Thames Gateway; and the greatly overlapping Thames Estuary around the tidal Thames to the east of London and including the waterway itself. Thames Valley Police is a formal body that takes its name from the river, covering three counties.
In an alternative name, derived from its long tidal reach up to Teddington Lock in south west London, the lower reaches of the river are called the Tideway. The section of the river running through Oxford is traditionally called the Isis.
The administrative powers of the Thames Conservancy have been taken on with modifications by the Environment Agency and, in respect of the Tideway part of the river, such powers are split between the agency and the Port of London Authority.
In non-administrative use, stemming directly from the river and its name are Thames Valley University, Thames Water, Thames Television productions, Thames & Hudson publishing, Thameslink (north-south railways passing through central London) and South Thames College. Historic entities include the Thames Ironworks and Shipbuilding Company.
Two broad canals link the river to other river basins: the Kennet and Avon Canal (Reading to Bath) and the Grand Union Canal (London to the Midlands). The Grand Union effectively bypassed the earlier, narrow and winding Oxford Canal which also remains open as a popular scenic recreational route. Three further cross-basin canals are disused but are in various stages of reconstruction: the Thames and Severn Canal (via Stroud), which operated until 1927 (to the west coast of England), the Wey and Arun Canal to Littlehampton, which operated until 1871 (to the south coast), and the Wilts and Berks Canal.
Rowing and sailing clubs are common along the Thames, which is navigable to such vessels. Kayaking and canoeing also take place. Major annual events include the Henley Royal Regatta and the Boat Race, while the Thames has been used during two Summer Olympic Games: 1908 (rowing);1948 (rowing and canoeing). Safe headwaters and reaches are a summer venue for organised swimming, which is prohibited on safety grounds in a stretch centred on Central London. Non-Olympic watersports with a lesser presence include skiffing and punting.
== Summary ==
With a total length of , the Thames is the longest river entirely in England and the second longest in the United Kingdom. It rises at Thames Head in Gloucestershire, and flows into the North Sea via the Thames Estuary. On its way, it passes through London, the country's capital, where the river is deep and navigable to ships; the Thames drains the whole of Greater London.〔(Ordnance Survey map, courtesy of English Heritage )〕 Its tidal section, reaching up to Teddington Lock, includes most of its London stretch and has a rise and fall of .
Along its course are 45 navigation locks with accompanying weirs. Its catchment area covers a large part of South Eastern and a small part of Western England and the river is fed by 38 named tributaries. The river contains over 80 islands. With its waters varying from freshwater to almost seawater, the Thames supports a variety of wildlife and has a number of adjoining Sites of Special Scientific Interest, with the largest being in the remaining parts of the North Kent Marshes and covering .〔(South Thames Estuary And Marshes SSSI ) Natural England. Retrieved 16 September 2013.〕
The marks of human activity, in some cases dating back to Pre-Roman Britain, are visible at various points along the river. These include a variety of structures connected with use of the river, such as navigations, bridges and watermills, as well as prehistoric burial mounds. A major maritime route is formed for much of its length for shipping and supplies: through the Port of London for international trade, internally along its length and by its connection to the British canal system. The river's position has put it at the centre of many events in British history, leading to it being described by John Burns as "liquid history".
Running through some of the driest parts of mainland Britain and heavily abstracted for drinking water, the Thames's discharge is low considering its length and breadth: the Severn has a discharge almost twice as large on average despite having a smaller basin area. In Scotland, the Tay achieves more than double the average discharge from a basin area that is 60% smaller.
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