The Knight Reservoir is a large pumped storage reservoir located in the

Borough of Elmbridge Elmbridge is a local government district with borough status in Surrey, England. Its principal towns and villages are Esher, Cobham, Walton-on-Thames, Weybridge and Molesey. It directly borders the London Borough of Richmond upon Thames and t ...

in Surrey. It was inaugurated in 1907 and stores up to 2,180 million litres of raw water abstracted from the River Thames prior to its treatment and supply to London and north Surrey. It is located south of the

River Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the R ...

, west of West

Molesey Molesey is a district of two twin towns, East Molesey and West Molesey, in the Borough of Elmbridge, Surrey, England, and is situated on the south bank of the River Thames. East and West Molesey share a high street, and there is a second retai ...

, and between Hurst Road (A3050) and Walton Road (B369). It is adjacent to, and west of, its twin Bessborough Reservoir.

History

In 1898 the

Southwark and Vauxhall Waterworks Company The Southwark and Vauxhall Waterworks Company was a utility company supplying water to parts of south London in England. The company was formed by the merger of the Southwark and Vauxhall water companies in 1845 and became part of the publicly ...

operated a water works at

Hampton Hampton may refer to: Places Australia *Hampton bioregion, an IBRA biogeographic region in Western Australia *Hampton, New South Wales *Hampton, Queensland, a town in the Toowoomba Region * Hampton, Victoria Canada * Hampton, New Brunswick *Ha ...

, Middlesex. To increase the raw water storage capacity the company sought legal powers to construct two reservoirs across the river from the Hampton works. This was achieved through the provisions of the ''Southwark and Vauxhall Water Act 1898'' (61 & 62 Vict. c. cxv) which empowered the company to build two storage reservoirs; an intake from the river Thames; a pump house, and filter beds. Work began in 1898 on the site of an old mansion called Apps Court. Construction was incomplete when, in 1902, the

Metropolitan Water Board The Metropolitan Water Board was a municipal body formed in 1903 to manage the water supply in London, UK. The members of the board were nominated by the local authorities within its area of supply. In 1904 it took over the water supply functi ...

(MWB) was formed under the terms of the ''Metropolitan Water Act 1902'' (2 Edw. 7. c.41). The MWB took over the assets of several companies including the Southwark and Vauxhall Waterworks Company and the partly built reservoirs at Walton. The MWB continued the construction and the reservoirs were inaugurated in 1907.

Specification

The Knight and Bessborough reservoirs have a combined area of and hold 1,198 million gallons. Other key details of the reservoirs are as follows. The embankment walls of the reservoirs have a puddle clay core extending down to the underlying blue

London clay The London Clay Formation is a marine geological formation of Ypresian (early Eocene Epoch, c. 56–49 million years ago) age which crops out in the southeast of England. The London Clay is well known for its fossil content. The fossils from t ...

. The inlet pipes and water discharge tower are adjacent to the north embankment. Water from the reservoirs was piped under the river and flowed by gravity to the filter beds at Hampton Water Works. The Metropolitan Water Board operated the reservoirs until the Board was abolished in 1974 under the provisions of the ''Water Act 1973'' (c. 37). Ownership and control was transferred to the

Thames Water Authority The Thames Water Authority was one of ten regional water authorities created in the UK on 1 April 1974 under the provisions of the Water Act 1973 to bring together all the water management functions of the region in one public body. Predece ...

(TWA). The water supply industry was privatised in 1989, and the TWA became

Thames Water Thames Water Utilities Ltd, known as Thames Water, is a large private utility company responsible for the public water supply and waste water treatment in most of Greater London, Luton, the Thames Valley, Surrey, Gloucestershire, north Wiltsh ...

. Knight and Bessborough Reservoirs are a Site of Special Scientific Interest.

Operations

Water was abstracted from the river Thames through an open intake channel (139 m long, 6.7 m wide, with a water depth of 2.4 m) and pumped into the reservoirs. There were four lift pumps which were originally driven by triple-expansion steam engines each rated at 373 kW at 135 rpm. Each engine was coupled to a two-stage

centrifugal pump Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic ...

capable of delivering 114 million litres/day. The reservoirs allowed some settlement of suspended solids, biological cleaning through exposure to sunlight, and provided a buffer storage volume to maintain capacity at times of low flow in the river. As originally conceived water from the reservoirs was piped under the river and flowed by gravity to the filter beds at Hampton Water Works. The difference in level between the reservoirs and the filter beds was 9.7 m. The flow of water drove three hydraulic turbines coupled to centrifugal pumps which were used to lift river water into the reservoirs. In addition to the Knight and Bessborough reservoirs there were four smaller rectangular reservoirs (each 750 ft by 550 ft, 229 m by 167 m) located east of the intake channel. In the 1920s a water treatment works was constructed to the north of the reservoirs. By 1933 this comprised six slow sand filters (each 220 ft by 170 ft, 67 m by 52 m) located west of the intake channel.Ordnance Survey 6-inch ''Surrey XII.NW'' (includes: East Molesey; Esher; Walton upon Thames; West Molesey.) Revised: 1938 In 1926 the steam engines were converted to single cylinder triple expansion steam pumps and

steam turbines A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbin ...

. Further filter beds were added in 1950 west of the pump house. Further plant was added as the demand for water grew, and when the Queen Elizabeth II reservoir was commissioned in 1962. The steam engines were replaced with electric motors in 1964.

References

Reservoirs in Surrey Borough of Elmbridge Sites of Special Scientific Interest in Surrey Thames Water reservoirs Drinking water reservoirs in England {{Surrey-geo-stub

History

Specification

Operations

See also

References