The Queen Mother Reservoir lies between the M4

M4 motorway

The M4 motorway links London with South Wales. It is part of the unsigned European route E30. Other major places directly accessible from M4 junctions are Reading, Swindon, Bristol, Newport, Cardiff and Swansea...

 and the M25

M25 motorway

The M25 motorway, or London Orbital, is a orbital motorway that almost encircles Greater London, England, in the United Kingdom. The motorway was first mooted early in the 20th century. A few sections, based on the now abandoned London Ringways plan, were constructed in the early 1970s and it ...

 to the west of London. It is 475 acres (1.9 km²) in size or about 1 km in diameter - making it one of the largest inland areas in Southern England. It is managed by Thames Water

Thames Water

Thames Water Utilities Ltd, known as Thames Water, is the private utility company responsible for the public water supply and waste water treatment in large parts of Greater London, the Thames Valley, Surrey, Gloucestershire, Wiltshire, Kent, and some other areas of in the United Kingdom...

.

This is one of a number of reservoirs to the west of London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 and was built in 1976. Its water is pumped from the River Thames

River Thames

The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

 nearby. The water improves in quality during its retention in the reservoir as solids settle and organic contaminants are adsorbed, absorbed and degraded through a combination of natural biological processes aided by sunlight and oxygenation. Water from the reservoir is treated (often using slow sand filter

Slow sand filter

Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water...

s) before being put into supply as London tap water.

The reservoir lies within the Colne Valley regional park

Colne Valley regional park

The Colne Valley regional park located to the west of Greater London contains a mixture of farmland, woodland and water, fifty miles of river and canal and over forty lakes. As well as providing homes and farms it is also a regionally important place recreation and internationally important for...

 and like other local reservoirs is popular for sailing and bird-watching. Petrel

Petrel

Petrels are tube-nosed seabirds in the bird order Procellariiformes. The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group...

s have been spotted at this reservoir.