Island Barn Reservoir was authorized by the Lambeth Water Act 1900 (63 & 64 Vict. c. cxli).[2] It was built by Sir Robert McAlpine[3] for the Metropolitan Water Board, and opened in 1911.[4] 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.[5]
Construction
The embankment walls have a puddle clay core extending down through a gravel layer to the underlying blue London clay. The outside face of the embankment is grassed, the inner face is lined with concrete slabs.[6]
The key dimensions of the Island Barn reservoir are as follows.[7][8][6][a]
Parameter
Value
Capacity
922 million gallons (4,091 Ml)
Surface area
121 acres (49 ha)
Perimeter
1 mile 1,200 yards (2,707 m)
Base to top of bank
35 ft (10.7 m)
Base to top water level
30 ft (9.1 m)
Height of bank
24 ft to 34 ft (7.3 to 10.4 m)
Depth of puddle core
15 ft to 25 ft (4.57 to 7.62 m)
Embankment volume
1.27 million tonnes
Maximum height of water
17.59 m AOD
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.[6]
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.[6]
For several years leakage through the embankment had been observed.[9] 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.[9]
Between 1992 and 1998 1.3 million tonnes of gravel were removed from the base of the reservoir.[6]
Sailing Club
Island Barn Reservoir Sailing Club hosts dinghysailing 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.