Llyn Cowlyd

Llyn Cowlyd is the deepest lake in northern Wales, a long narrow reservoir high in Snowdonia National Park at the head of Cwm Cowlyd. It sits on the south-eastern edge of the Carneddau range at 370 metres above sea level, measuring 3.0 kilometres long and up to 400 metres wide. The lake has a mean depth of 33 metres and reaches 70 metres at its deepest point. Its water level was raised twice by dams, increasing the depth by 14 metres. The surrounding hills drop steeply to the water’s edge, leaving the shoreline bare of trees and giving the scene a bleak appearance. The lake supplies water to Conwy and Colwyn Bay through an underground pipe network over 60 kilometres long. A separate large pipeline carries water to the power station at Dolgarrog, built in 1925 to support the aluminium works. During World War II, a shepherd named Wil Roberts patrolled this pipeline, finding only a crashed aircraft in 1944. The lake also generates hydro-electricity, sharing this role with nearby Llyn Eigiau, connected by tunnel in 1919. Henry Joseph Jack, chairman of the North Wales Power and Traction Company, played a key role in developing electricity production here. Visitors reach the lake by road from Trefriw, though vehicles stop at a gate 1.2 kilometres away. A good path runs along the north-western shore, offering walking routes from Capel Curig or the ridge of Cefn Cyfarwydd. The outflow, Afon Ddu, flows into the River Conwy near Dolgarrog, where the river has cut a gorge popular for gorge walking. Remains of the old dam construction site, including a stone quarry and winding drum, can still be seen. The dam itself, completed in 1921, has a concrete core and rock embankment, with a stone apron protecting it from wave action.