Llyn Celyn

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Llyn Celyn dam
Tree stumps exposed by low water

Llyn Celyn is a large reservoir and artificial lake in Merionethshire. It was constructed between 1960 and 1965 in the valley of the River Tryweryn.

The lake measures roughly 2½ miles long by a mile wide, and has a maximum depth of 140 feet. It has the capacity to hold Error: mismatched units of water.[1]

The reservoir was built by the Liverpool Corporation to provide water to that thirsty city and it was originally to be named Llyn Tryweryn Mawr ("Great Tryweryn Lake"), but in September 1964 the Corporation agreed to the name change following a letter by the 'Tryweryn Defence Committee'.[2]

Construction and opposition

The project to create the reservoir was one of many across Great Britain over the years, through which valleys have been flooded across the land with barely a hill county escaping. This was a late project, in the radical 1960s, and proved a controversial one.

Construction of the reservoir involved flooding the village of Capel Celyn and adjacent farmland, which was deeply unpopular locally. Much of the opposition was brought about because the village was a stronghold of the Welsh language, whilst the reservoir was being built to supply a far-off city. The legislation enabling the development was introduced in the late 1950s and passed despite the opposition of all but one of the Members of Parliament for Welsh constituencies, and in those unsettled times as the 1960s were ready to dawn, it produced an increase in support for the Welsh nationalist party, Plaid Cymru.

The official opening took place on 21 October 1965 in the presence of representatives from Liverpool council. The ceremony lasted less than 3 minutes, for protesters had cut the microphone wires, and the chants of the hundreds of protesters made the speeches inaudible.

In October 2005, Liverpool City Council passed a public apology for the incident, that We realise the hurt of forty years ago when the Tryweryn Valley was transformed into a reservoir to help meet the water needs of Liverpool. For any insensitivity by our predecessor Council at that time, we apologise", though the water still supplies a city still growing.

Operation of reservoir

Tryweryn memorial chapel at Llyn Celyn

The reservoir was constructed in order to help maintain the flow in the River Dee, so that drinking water could be abstracted further downstream as part of the regulation scheme. These abstractions include one at Huntington water treatment works in Chester, which supplies water to Liverpool and the Wirral.

The reservoir is contained behind a rock gravity dam and, at its upper end, it runs between two mountains, Arenig Fawr and Arenig Fach. Water is released from the reservoir into the River Tryweryn which flows into the River Dee. Most of the water passes through a small hydro-electricity plant to supply electricity to the National Grid. The released water first flows into a stilling basin and then down the narrow and rocky valley of the River Tryweryn. This section of the river provides facilities for international level white-water canoeing, and rafting at the Canolfan Tryweryn National White-water Centre. Some water in the reservoir is held in reserve to make special release down the river for specific white-water events. Because the reservoir's principal purpose is to support low river flows in the main River Dee, the best conditions for white-water occur during long dry spells in summer when maximum releases are made. During wet weather the releases are usually throttled back to a minimal maintenance flow unless a planned release for recreational activities has been agreed.

Diversions and closures of transport links

The building of the reservoir also contributed to the final closure of the GWR branch line from Bala to Blaenau Ffestiniog.[3] Passenger trains had ceased running in 1960, and the last freight train ran in 1961. The line was subsequently flooded by the lake, and the base of the dam also crosses it. Liverpool Council had in fact planned a railway diversion, but this was never built as the British Transport Commission had decided to close the line. As a result of this, Liverpool Council decided to contribute towards the cost of the new main road (the A4212, which was built across the pass from Bala to Trawsfynydd around the north side of the lake), and also towards the cost of a line linking the two stations in Blaenau Ffestiniog.

See also

Outside links

52°57′0″N 3°41′38″W / 52.95°N 3.69389°W / 52.95; -3.69389Coordinates: 52°57′0″N 3°41′38″W / 52.95°N 3.69389°W / 52.95; -3.69389


  1. National Library of Wales page, "Celyn lake held a capacity of 71,200 mega litres of water, the biggest dam in Wales"
  2. Capel Celyn, Ten Years of Destruction: 1955 - 1965, by Einion Thomas, published by Cyhoeddiadau Barddas & Gwynedd Council, 2007, ISBN 978-1-900437-92-9
  3. http://www.penmorfa.com/Conwy/six.htm penmorfa.com