Llyn Eigiau historique, lac et barrage, montrant une violation dans le vieux mur de barrage à gauche après 1911, catastrophe, au nord du Pays de Galles Snowdonia
The main feeder for llyn Eigiau is the river, Afon Eigiau and the outflow from the lake is called Afon Porth-llwyd which flows into the Coedty reservoir to the Dolgarrog hydro electric power station. Water is also fed into the lake by a tunnel from a stream below lake Dulyn and another larger tunnel takes water to nearby Llyn Cowlyd. The Eigiau reservoir provides water for Dolgarrog's low head scheme turbines, via a 3km pipeline from a catchment area of around 27 square kilometres. In 1911 a 30 ft high and nearly a mile long dam was built to raise the lake by 6ft to supply water to Dolgarrog Power Station to supply electricity to the nearby Aluminium works. In 1928 after heavy rainfall, the dam broke and water flowed down to the Coedty reservoir which also burst. Millions of gallons of water poured into the village of Dolgarrog where 17 lives were lost. A new power station was built in 1925 and a study of the dam today shows that the foundations were quite insufficient. The breach in the dam can be seen to the far left. Llyn Eigiau today covers about 120 acres and is about 32ft deep. After its original construction the dam the area would have been twice its present size.
