Llyn Alaw (meaning: ''Lily Lake'') is a man-made

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

Anglesey Anglesey ( ; ) is an island off the north-west coast of Wales. It forms the bulk of the Principal areas of Wales, county known as the Isle of Anglesey, which also includes Holy Island, Anglesey, Holy Island () and some islets and Skerry, sker ...

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

managed by

Dŵr Cymru Welsh Water Dŵr Cymru Welsh Water is a not-for-profit company which supplies drinking water and wastewater services to most of Wales and parts of western England that border Wales. In total, it serves around 1.4 million households and businesses and over thr ...

. It is a shallow lake and was built in 1966. It is a

Site of Special Scientific Interest A Site of Special Scientific Interest (SSSI) in Great Britain, or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland, is a conservation designation denoting a protected area in the United Kingdom and Isle ...

and a destination for overwintering birds.

History

It is used to supply drinking water to the northern half of the island and does so at a rate of 35 million litres a day. Filling began in November 1965, flooding the existing marsh of Cors y Bol, and was completed in January 1966. It was officially opened on 21 October 1966. Due to the area being marshland no houses or farms, let alone hamlets or villages had to be abandoned to create it. The catchment is largely

agricultural Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created f ...

, and few notable rivers feed into the lake. The storage capacity is mostly generated through trapping winter rainfall and drawing down the level in the summer months. The reservoir itself is 4.3 kilometres long with a surface area of 3.6 km² making it the largest body of water on the island, but it only ever reaches a depth of 5.2 metres.

The reservoir

The lake is a designated SSSI because of the variety and numbers of wild fowl visiting the lake, especially overwintering birds including the

Eurasian Teal The Eurasian teal (''Anas crecca''), common teal, or Eurasian green-winged teal is a common and widespread duck that breeds in temperate Eurosiberia and migrates south in winter. The Eurasian teal is often called simply the teal due to being th ...

northern shoveler The northern shoveler (; ''Spatula clypeata''), known simply in Britain as the shoveler, is a common and widespread duck. It breeds in northern areas of Europe and throughout the Palearctic and across most of North America, and winters in southe ...

and

whooper swan The whooper swan ( /ˈhuːpə(ɹ) swɒn/ "hooper swan"; ''Cygnus cygnus''), also known as the common swan, is a large northern hemisphere swan. It is the Eurasian counterpart of the North American trumpeter swan, and the type species for the genu ...

. Other waterfowl include

mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

, wigeon,

common goldeneye The common goldeneye or simply goldeneye (''Bucephala clangula'') is a medium-sized sea duck of the genus ''Goldeneye (duck), Bucephala'', the goldeneyes. Its closest relative is the similar Barrow's goldeneye. The genus name is derived from th ...

, common pochard,

tufted duck The tufted duck (or tufted pochard) (''Aythya fuligula'') is a small diving duck with a population of nearly one million birds, found in northern Eurasia. They are partially migratory. The scientific name is derived from Ancient Greek , an unide ...

, ruddy duck and occasionally

pink-footed goose The pink-footed goose (''Anser brachyrhynchus'') is a goose which breeds in eastern Greenland, Iceland, Svalbard, and recently Novaya Zemlya. It is migratory, wintering in northwest Europe, especially Ireland, Great Britain, the Netherlands, a ...

. The lake is only a few metres deep as it was formed by flooding a former bog. The surrounding area is flat with a marshy area to the north of the lake. The shore is bordered by vegetation and has bushes and scrub in some areas. There are a number of low islets and in summer, when water levels are low, the lake is bordered by mud flats. Facilities for visitors include a car park, a visitor centre, two bird hides, three picnic sites and several miles of footpaths, although these do not allow visitors to make a complete circuit of the lake. Recent developments have included the provision of

nature conservation Nature conservation is the ethic/moral philosophy and conservation movement focused on protecting species from extinction, maintaining and restoring habitats, enhancing ecosystem services, and protecting biological diversity. A range of values ...

facilities and way-marked walks around the margin. The lake has an active fishery.Dwr Cymru Fishing Guide
/ref> The lake contains wild

brown trout The brown trout (''Salmo trutta'') is a species of salmonid ray-finned fish and the most widely distributed species of the genus ''Salmo'', endemic to most of Europe, West Asia and parts of North Africa, and has been widely introduced globally ...

and is stocked with

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...

and is considered one of the most productive lakes in Wales.

References

{{authority control Llannerch-y-medd Rhosybol Tref Alaw Alaw Sites of Special Scientific Interest on Anglesey