The Kennet near Axford.
|Towns||Marlborough, Hungerford, Newbury|
|⁃ location||Swallowhead Spring, near Silbury Hill, Wiltshire, United Kingdom|
|⁃ elevation||200 m (660 ft)|
|Reading, Berkshire, United Kingdom|
|40 m (130 ft)|
|Length||72 km (45 mi)|
|⁃ location||Theale, Berkshire|
|⁃ average||9.75 m3/s (344 cu ft/s)|
|⁃ minimum||0.93 m3/s (33 cu ft/s)21 August 1976|
|⁃ maximum||70.0 m3/s (2,470 cu ft/s)11 June 1971|
|⁃ location||Newbury, Berkshire|
|⁃ average||4.64 m3/s (164 cu ft/s)|
|⁃ location||Knighton, Wiltshire|
|⁃ average||2.50 m3/s (88 cu ft/s)|
|⁃ location||Marlborough, Wiltshire|
|⁃ average||0.85 m3/s (30 cu ft/s)|
|⁃ left||River Og, River Lambourn|
|⁃ right||River Dun, River Enborne, Clayhill Brook, Foudry Brook|
The Kennet is a river in the south of England, and a tributary of the River Thames. The lower reaches of the river are navigable to river craft and are known as the Kennet Navigation. This, together with the Avon Navigation, the Kennet and Avon Canal and the Thames, links the cities of Bristol and London. The former local government district of Kennet in Wiltshire was named after it.
The River Kennet from near its sources west of Marlborough in Wiltshire down to Woolhampton in Berkshire is a 111.1-hectare (275-acre) biological Site of Special Scientific Interest (SSSI). This is primarily because it has an extensive range of rare plants and animals that are unique to chalk watercourses.
One of the Kennet's sources is Swallowhead Spring near Silbury Hill in Wiltshire, the other being a collection of tributaries north of Avebury near the rural settlements of Uffcott and Broad Hinton which flow south past Avebury and join up with the waters from Swallowhead Spring. In these early stages it passes close by many prehistoric sites including Avebury Henge, West Kennet Long Barrow and Silbury Hill. The land drained by upper reaches has a low water table owing to its position in the North Wessex Downs which is mostly chalk as the upper subsoil, as such many of these stretches are winterbournes depending[clarification needed] on precipitation and surrounding soil type.
The upper reaches of the River Kennet have two tributaries: the River Og which flows into the Kennet at Marlborough and the River Dun which enters at Hungerford. The Kennet's principal tributaries below Marlborough are the River Lambourn, the River Enborne and the Foudry Brook. For six miles (10 km) to the west of, and through, Reading, the Kennet supports a secondary channel (corollary), the Holy Brook, which formerly powered the water mills of Reading Abbey.
The Horseshoe Bridge at Kennet Mouth, a timber-clad iron-truss structure, was built in 1891 as a way for horses towing barges along the Thames to cross the Kennet.
Going upstream, the first mile of the river, from Kennet Mouth to the High Bridge in Reading, has been navigable since at least the 13th century, providing wharfage for both the townspeople and Reading Abbey. Originally this short stretch of navigable river was under the control of the Abbey; today, including Blake's Lock, it is administered by the Environment Agency as if it were part of the River Thames.
From High Bridge through to Newbury, the river was made navigable between 1718 and 1723 under the supervision of the engineer John Hore of Newbury. Known as the Kennet Navigation, this stretch of the river is now administered by the Canal & River Trust as part of the Kennet and Avon Canal. Throughout the navigation, stretches of natural river bed alternate with 11 miles (18 km) of artificially created lock cuts, and a series of locks including County, Fobney, Southcote, Burghfield, Garston, Sheffield, Sulhamstead and Tyle Mill overcome a rise of 130 feet (40 m).
The River Kennet is a haven for various plants and animals. Its course takes it through the North Wessex Downs Area of Outstanding Natural Beauty, and the river between Marlborough and Woolhampton is designated a Site of Special Scientific Interest (SSSI). The protection that this status affords the Kennet means that many endangered species of plants and animals can be found here. The white drifts of water crowfoot (Ranunculus) in early summer are characteristic of chalk and limestone rivers; there are superb displays by the footbridge at Chilton Foliat, and by the road bridge in Hungerford.
Animal species such as the water vole, grass snake, reed bunting, brown trout, and brook lamprey flourish here, despite being in decline in other parts of the country. Crayfish are very common in parts of the river. However, most, if not all, are now the alien American signal crayfish, having escaped from crayfish farms, which has replaced the native white-clawed crayfish in most southern rivers, although a small population still survives in the River Lambourn. And not forgetting the foundation to supporting this varied wildlife food chain, there are the insects, many hundreds of species, common and rare, that can be found in and around the River Kennet. There are large hatches of mayflies, whose long-tailed, short-lived adults are a favourite food of trout; many species of water beetle and insect larvae. Caddisflies are also very numerous, especially in the late summer. Alongside the river, the reed beds, grasses and other vegetation support many other insect species, including the scarlet tiger moth, poplar hawk moths and privet hawks.
Throughout its history, water mills on the Kennet have been a source of power for various pre-industrial and industrial activities. In places the river has been built up to provide an additional head of water to drive the mills. Three mills remain in Ramsbury alone, and there are many disused or former mill sites, such as at Southcote, Burghfield, Sulhamstead, Aldermaston, Thatcham, Newbury, and Hungerford. Aside from the mills, in the 17th and 18th centuries the river water was also used for the brewing and tanning industries of Ramsbury and Marlborough.
It was formerly known as the "Cunnit". The name is likely derived from the Roman settlement at the foot of the valley named Cunetio (within the large village of Mildenhall). The sound of the name seems to be a Celtic British dialect name, preceding the Roman occupation, like the majority of Roman town names in Britain. (The frequent Celtic stem "cun-" means "hound", cf modern Welsh ci, c?n "dog"; for details see this Wiktionary article.)
In July 2013 the Environment Agency investigated an insect kill which resulted when a small quantity (estimated to be two teaspoonfuls (10 millilitres)), of chlorpyrifos, an organophosphate insecticide used in ant poison and available in garden centres, was flushed into the river killing the freshwater shrimp and most other arthropods on the stretch of the river between Marlborough and Hungerford. The dead insects sank to the bottom of the river and rotted, resulting in a bad smell, but no fish seemed to have been killed. However, without insects and shrimps to feed on, many of the fish, birds and amphibians that use the river would be likely to fade away and die. The poison was diluted and removed by the flow of the stream.