Llyn Trawsfynydd is a large man-made reservoir situated near the village of Trawsfynydd in Gwynedd, North Wales. With a total surface area of 4.8 km² (1,180 acres) the reservoir is slightly more extensive than Wales's largest natural lake, Llyn Tegid (which covers an area of 4.5 km²).
Originally created in 1928 as the header reservoir for the Maentwrog hydro-electric power station, Llyn Trawsfynydd was subsequently also used as the source of cooling water for the Trawsfynydd nuclear power station which generated electricity for the UK National Grid. The nuclear power station, now in the process of decommissioning, no longer generates electricity, but the lake continues to be used for hydroelectricity generation.
Looking north to the power station