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

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

Anglesey Anglesey (; cy, (Ynys) Môn ) is an island off the north-west coast of Wales. It forms a principal area known as the Isle of Anglesey, that includes Holy Island across the narrow Cymyran Strait and some islets and skerries. Anglesey island ...

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

managed by Dŵr Cymru Welsh Water. 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 of ...

and a destination for over-wintering 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 or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

, 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 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 of ...

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 across the Palearctic and across most of North America, wintering in southern Euro ...

and

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

. 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, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

wigeon The wigeons or widgeons are a group of birds, dabbling ducks currently classified in the genus ''Mareca'' along with two other species. There are three extant species of wigeon, in addition to one recently extinct species. Biology There are t ...

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

common pochard The common pochard (; ''Aythya ferina'') is a medium-sized diving duck. The scientific name is derived from Greek '' aithuia'', an unidentified seabird mentioned by authors including Hesychius and Aristotle, and Latin ''ferina'', "wild game", f ...

tufted duck The tufted duck or tufted pochard (''Aythya fuligula'') is a small diving duck with a population of close to one million birds, found in northern Eurasia. The scientific name is derived from Ancient Greek '' aithuia'', an unidentified seabird ment ...

ruddy duck The ruddy duck (''Oxyura jamaicensis'') is a duck from North America and one of the stiff-tailed ducks. The genus name is derived from Ancient Greek ''oxus'', "sharp", and ''oura'', "tail", and ''jamaicensis'' is "from Jamaica". Taxonomy The ru ...

and occasionally

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

. 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 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 unde ...

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 European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

and is stocked with

rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributaries of the Pacific Ocean in Asia and North America. The steelhead (sometimes called "steelhead trout") is an anadromous (sea-run) form of the coasta ...

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