William Girling Reservoir (map) is part of the Lee Valley reservoir chain that supplies London with drinking water.
The reservoir covers 135 hectares (334 acres) with a perimeter of 5.6 km (3.5 miles). It has a capacity of 16.5 billion litres (3.5 billion gallons). There is no public access, but much of the water can be viewed from Mansfield Park, near the eastern shore. The water is a Site of Special Scientific Interest (SSSI) as a major wintering ground for wildfowl and wetland birds.
The reservoir is on the eastern edge of the London Borough of Enfield (bordering the London Borough of Waltham Forest). It is owned by Thames Water.
William Girling Reservoir was conceived as part of an overall plan for the Lee Valley at the end of the 19th century, but the Metropolitan Water Board did not start work on it until 1936. Construction was delayed by two landslips, which led to modifications to the design. It was delayed again by the outbreak of the Second World War and was not finally completed until 1951, when it was officially opened on 4 September by William Girling, a Labour politician and chairman of the Metropolitan Water Board. In 1974 the water board was wound up and the reservoirs passed into the ownership of the newly formed Thames Water Authority.
The geology of the site is alluvium underlain by river terrace gravels and in turn overlying the London Clay formation. The reservoir is enclosed by an earthen embankment with a maximum height of 14.3m (47ft) and is surrounded by a narrow strip of land. The Lea Valley navigation and the River Lea pass on either side in canals. To the south of the reservoir (accessible from Russell Road) is a flood relief channel that often attracts waders.
With its large water surface and lack of human disturbance, the reservoir attracts migratory wildfowl, gulls and other wetland birds in large numbers. In winter it regularly support nationally important populations of Shoveler and Great Crested Grebe and important numbers of Goldeneye and Goosander. It is Britain’s major site for wintering Black-necked Grebe, with 20 or more often present. Winters also commonly see at least one long-staying Great Northern Diver and occasionally other divers.
The reservoir supports one of London’s principal winter gull roosts. A count in January 2009 totalled 17,500 Black-headed Gull, 2,100 Common Gull, 1,560 Lesser Black-backed Gull, 570 Herring Gull, 6 Great Black-backed Gull and 2 Mediterranean Gull.
The reservoir is also a noted site for migrant wetland birds on spring and autumn passage, particularly in the flood relief channel south of the reservoir.
The reservoir can be viewed by ’scoping it from the slopes of Mansfield Park, Chingford (map). To reach the park from the North Circular Road (A406) eastbound, cross over the Lea Valley Viaduct and turn left onto the A1009 (Hall Lane). At a roundabout continue straight ahead on the A1037 (Waltham Way). Just after a golf range on the left, turn right into Eatons Mead and continue into Valley Side (for satnav, key in E4 7SP). Mansfield Park is on the right.
There is no public access to the reservoir itself. The flood relief channel is accessible from Russell Road, off Hall Lane/Waltham Way.
The Old Hall Tavern on Hall Lane (tel 02085292405) serves typical pub food.
This page has been cobbled together from various internet sources by someone who has never visited the site but thinks that it deserves a page on the London Bird Club Wiki. If you are familiar with the site, please correct, expand and/or update the information.