The Thames is a river that flows through southern England, connecting London to the North Sea. It is 346 km long. The catchment area is 12,935 km².
Description of the flow
Rises about 1 km north of the village of Kemble, near Cirencester in the Cotswolds. It flows through the towns of Lechlade, Oxford (under the Latin name Isis), Abingdon, Wallingford, Reading, Henley-on-Thames, Marlow, Maidenhead, Windsor, Eton, Staines, Weybridge and then flows to the edge of Greater London. From the Greater London border it flows along Syon House, Hampton Court, Kingston, Richmond and Kew until it reaches central London. From there it flows through Greenwich, Dartford and, at Southend-on-Sea, into the North Sea, forming an estuary. The width of the river in London varies from 200 to 250 m, reaching 650 m at the start of the estuary near the edge of the city and nearly 16 km near the mouth.
Water regime
The Thames is characterised by a rainfall (pluvial) runoff regime. The average flow in London is up to 66 m³/s. This is less than some other British rivers such as the Severn and Tay. It reaches its highest water levels in spring. Ice is only present on the river in exceptionally hard winters. The tidal height in London is 6 to 6.5 m and the tidal surge reaches as far as Teddington, where the channel is dammed. Levees have been built to protect the river and estuary from flooding and embankments have been built in the towns.
The Thames basin
The Thames catchment can be divided into non-tidal and tidal.
In the stretch from the source to Teddington, the non-tidal catchment area includes 38 main tributaries and several smaller ones, covering about 9,948 km². Among the main tributaries in this area are the Churn, Leach, Cole, Coln, Windrush, Evenlode, Cherwell, Ock, Thame, Pang, Kennet, London, Colne, Wey, and Mole.
The tidal catchment begins about 90km offshore where the Thames is affected by tidal influence from the North Sea. This causes the water in the river to be brackish (partly saline). The main tributaries in this area are the Brent, Wandle, Effra, Westbourne, Fleet, Ravensbourne, Lea, Darent, Ingrebourne.
The area of the Thames catchment (if the Medway catchment is included) is 12 935 km².
