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The River Thames (/tɛmz/ (listen) TEMZ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At 215 miles (346 km), it is the longest river entirely in England and the second-longest in the United Kingdom, after the River Severn.

Quick facts: River Thames, Etymology, Location, Country, C...
River Thames
Map of the Thames within southern England
EtymologyProto-Celtic *tamēssa, possibly meaning "dark"
Location
CountryUnited Kingdom (England)
CountiesGloucestershire, Wiltshire, Oxfordshire, Berkshire, Buckinghamshire, Surrey, Greater London, Kent, Essex
Towns/citiesCricklade, Lechlade, Oxford, Abingdon, Wallingford, Reading, Henley-on-Thames, Marlow, Maidenhead, Windsor, Staines-upon-Thames, Walton-on-Thames, Sunbury-on-Thames, Kingston upon Thames, Twickenham, London (inc. the City), Dagenham, Erith, Dartford, Grays, Gravesend
Physical characteristics
Source 
  locationThames Head, Gloucestershire, UK
  coordinates51°41′40″N 02°01′47″W
  elevation110 m (360 ft)
2nd source 
  locationUllenwood, Gloucestershire, UK
  coordinates51°50′49″N 02°04′41″W
  elevation214 m (702 ft)
MouthThames Estuary, North Sea
  location
Southend-on-Sea, Essex, UK
  coordinates
51°30′00″N 00°36′36″E
  elevation
0 m (0 ft)
Length346 km (215 mi)
Basin size12,935 km2 (4,994 sq mi)
Discharge 
  locationLondon
  average65.8 m3/s (2,320 cu ft/s)
  maximum370 m3/s (13,000 cu ft/s)
Discharge 
  locationentering Oxford
  average17.6 m3/s (620 cu ft/s)
Discharge 
  locationleaving Oxford
  average24.8 m3/s (880 cu ft/s)
Discharge 
  locationReading
  average39.7 m3/s (1,400 cu ft/s)
Discharge 
  locationWindsor
  average59.3 m3/s (2,090 cu ft/s)
Close

The river rises at Thames Head in Gloucestershire, and flows into the North Sea near Tilbury, Essex and Gravesend, Kent, via the Thames Estuary. From the west it flows through Oxford (where it is sometimes called the Isis), Reading, Henley-on-Thames and Windsor. The Thames also drains the whole of Greater London.[1]

In August 2022, the source of the river moved five miles to beyond Somerford Keynes due to the heatwave in July 2022.[2]

The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock. Its tidal section includes most of its London stretch and has a rise and fall of 23 ft (7 m). From Oxford to the Estuary the Thames drops by 55 metres. Running through some of the drier parts of mainland Britain and heavily abstracted for drinking water, the Thames' discharge is low considering its length and breadth: the Severn has a discharge almost twice as large on average despite having a smaller drainage basin. In Scotland, the Tay achieves more than double the Thames' average discharge from a drainage basin that is 60% smaller.

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; the river is fed by at least 50 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 North Kent Marshes and covering 20.4 sq mi (5,289 ha).[3]

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