Llyn Cefni is a small

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 ...

in the centre of

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 ...

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 ...

which is managed by

Welsh Water Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peopl ...

and Hamdden Ltd, while the fishery is managed by the Cefni Angling Association. The reservoir is located just northwest of the island's county town of

Llangefni Llangefni (meaning "church on the River Cefni", ) is the county town of Anglesey in Wales and contains the principal offices of the Isle of Anglesey County Council. United Kingdom Census 2011 recorded Llangefni's population as 5,116 people, maki ...

History

During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, a water scheme was devised for the town of

in central Anglesey. It involved water from a local source being pumped to two settling tanks in the Dingle part of the town. From here the water was pumped across the river to a reservoir and water tower, on the site of the present Pennant Estate. These arrangements became redundant with the building of the Cefni Reservoir, which was completed in 1951, but the settling tanks and pumping station survive in Llangefni to this day. The new scheme was designed to supply most of the water needs for the people of Anglesey for the foreseeable future.

Geography

The

Afon Cefni Afon Cefni is one of the major rivers on the island of Anglesey, Wales. It is long. Its source is near to the village of Capel Coch, before flowing through Bodffordd and into Llyn Cefni in the centre of the island. It continues to run south th ...

is one of the main rivers of Anglesey. It was dammed about northwest of Llangefni, just below the confluence of the tributary from

Tregaian Llanddyfnan is a village and community in Anglesey, Wales, located north east of Llangefni, north west of Menai Bridge and west of Beaumaris. Description The community includes the villages of Capel Coch, Ceint, Llanddyfnan, Llangwyllog, M ...

with other streams flowing from the northwest, and the reservoir has a catchment area of about . The reservoir is fed by two main streams, the Afon Frogwy entering from the west and the Afon Erddreiniog from the north east end. With a maximum length of and a total water surface area of , Llyn Cefni is the second largest body of water on the island after

Llyn Alaw Llyn Alaw (meaning: ''Lily Lake'') is a man-made reservoir on Anglesey, North Wales managed by Dŵr Cymru Welsh Water. It is a shallow lake and was built in 1966. It is a Site of Special Scientific Interest and a destination for over-wintering ...

, also a reservoir. There is a

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

on the south-east edge of the reservoir, next to which is a car park. The northeastern end of the reservoir and the immediate surrounding area have been designated as a

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...

, and as a further measure of conservation, a plantation of trees runs along its north shore. The tracks of the

Anglesey Central Railway The Anglesey Central Railway (Welsh: ''Lein Amlwch'', ''Amlwch Line'') was a standard-gauge railway in Anglesey, Wales, connecting the port of Amlwch and the county town of Llangefni with the North Wales Coast Line at Gaerwen. Built as an i ...

, although no longer used, still run over an

embankment Embankment may refer to: Geology and geography * A levee, an artificial bank raised above the immediately surrounding land to redirect or prevent flooding by a river, lake or sea * Embankment (earthworks), a raised bank to carry a road, railwa ...

which crosses the water. The reservoir is easily accessible from Llangefni, as well defined paths run from the town through the local nature reserve, The Dingle, one of the few ancient woodland sites on the island. It can also be accessed by the Lôn Las Cefni cycleway which follows the Afon Cefni from The Dingle and divides at the dam. In the summer of 2011, toxic

blue-green algae Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, bl ...

were found in the reservoir and visitors were advised to avoid contact with the water.

References

{{authority control Cefni