The Island Barn Reservoir lies south of the

River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, se ...

in England at

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 north of

Lower Green, Esher Lower Green is a residential and commercial area within Esher, in Surrey, England, on the banks of the River Ember and River Mole. The area has many businesses, most of them in the commercial complex comprising Sandown Industrial Complex and Roy ...

. The reservoir is large with a capacity of 992 million gallons and is managed by

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 Wiltshir ...

. It is within the borough of Elmbridge and is surrounded by the

River Mole The River Mole is a tributary of the River Thames in southern England. It rises in West Sussex near Gatwick Airport and flows northwest through Surrey for to the Thames at Hampton Court Palace. The river gives its name to the Surrey district ...

to the west and the

River Ember The River Ember is a short river in the north of Surrey, England — a channel of the River Mole which splits in two south of Island Barn Reservoir, between East Molesey and Lower Green, Esher. The Ember, the larger channel, flows in an easter ...

to the east.

Queen Elizabeth II Reservoir The Queen Elizabeth II Reservoir lies to the south of the River Thames and to the west of the Island Barn Reservoir. To the north are the Bessborough and Knight reservoirs. The A3050 runs to the north of the reservoir and it is situated in Walt ...

is a larger reservoir to the West.

History

Island Barn Reservoir was authorized by the ''Lambeth Water Act 1900'' (63 & 64 Vict. c. cxli) . It was built by

Sir Robert McAlpine Sir Robert McAlpine Limited is a family-owned building and civil engineering company based in Hemel Hempstead, England. It carries out engineering and construction in the infrastructure, heritage, commercial, arena and stadium, healthcare, educa ...

for 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 ...

, and opened in 1911. The contract was valued at £152,727. The reservoir was named after Island Barn Farm, which previously existed on the site, and was completely surrounded by the rivers Ember and Mole.

Construction

The embankment walls have a puddle clay core extending down through a gravel layer 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 outside face of the embankment is grassed, the inner face is lined with concrete slabs. The key dimensions of the Island Barn reservoir are as follows.

Operation

Raw water, from the River Thames, is pumped 2.7 km through a 54 inch (1.34 m) diameter pipeline from the pump house at Walton Water Works adjacent to the Knight reservoir. The reservoir can also be filled by gravity from the Bessborough and Knight reservoirs. The reservoir allows some settlement of suspended solids; biological cleaning through exposure to sunlight; and provides a buffer storage volume to maintain capacity at times of low flow in the river. Water is supplied to the Surbiton water treatment works. For several years leakage through the embankment had been observed. A survey identified three areas of leakage. In 2017 interlocking sheet piling 18.5 m long was driven vertically through the centre of the embankment into the London clay to stop the leakage. Between 1992 and 1998 1.3 million tonnes of gravel were removed from the base of the reservoir.

Sailing Club

Island Barn Reservoir Sailing Club hosts

dinghy A dinghy is a type of small boat, often carried or towed by a larger vessel for use as a tender. Utility dinghies are usually rowboats or have an outboard motor. Some are rigged for sailing but they differ from sailing dinghies, which ...

sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' (land yacht) over a chosen cour ...

races and training at the reservoir. Among many successful current and past members has been Fireball world champion and ISO designer John Caig and British Olympic, European Champion and World Cup sailor Nicola Groves. The reservoir is a bird watching site and

Black-necked grebe The black-necked grebe or eared grebe (''Podiceps nigricollis'') is a member of the grebe family of water birds. It was described in 1831 by Christian Ludwig Brehm. There are currently three accepted subspecies, including the nominate subspecie ...

s have been sighted here.Thames Water official website - Birdwatching
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Gallery

Image:Islandbarn01.JPG, Outlet towers at Island Barn Reservoir Image:Island Barn Reservoir IMGP0993.JPG, Interior from the Sailing Club

References