Llyn Celyn (Tryweryn Reservoir)
Tryweryn Valley, Gwynedd, Wales, UK · 1960-1965 (construction began 1960, completed 1965)
The judgement call
Account-gated at launchThe project was highly controversial due to the compulsory purchase and flooding of Capel Celyn, a Welsh-speaking village, to supply water to Liverpool. - It became a symbol of Welsh nationalism and resistance against external control over Welsh resources. - The construction highlighted the tension between regional water needs and local community impact.
Key engineering challenges
Constructing a large reservoir in a valley, requiring the flooding of a village (Capel Celyn). - Managing the social and political controversy surrounding the project, particularly regarding its impact on Welsh language and culture. - Diverting high voltage cables and constructing a new haulage road as part of the infrastructure.
Project facts
- Client / owner
- Liverpool Corporation Waterworks (now Dŵr Cymru Welsh Water)
- Lead contractor
- —
- Lead designers
- —
- Project type
- new build
- Scale
- UK's largest spillway (mentioned in one source); involved flooding of the Tryweryn Valley.
- Disciplines
- civil; hydraulic; environmental
- Standards & frameworks
- Relevant UK dam construction and water supply regulations of the era.
Sources: "Llyn Celyn improvement work", Dŵr Cymru Welsh Water, https://corporate.dwrcymru.com/en/community/investment-projects/llyn-celyn - "The Drowning of Tryweryn Valley", National Library of Wales, https://www.library.wales/discover-learn/education/learning-resources/tryweryn - "The UK's Largest Spillway at Llyn Celyn Reservoir - CSF's Progress", Concrete Structures & Foundations, https://www.concretesf.co.uk/post/the-addition-of-the-uks-largest-spillway-at-llyn-celyn-reservoir---csfs-progress-on-the-project - "Tryweryn flooding", Wikipedia, https://en.wikipedia.org/wiki/Tryweryn_flooding