The mountain lake Arenig Fach and lies 1487 feet above sea level. It was surveyed by Thomas Telford c.1830 in order to supply the Ellesmere Canal with an additional source of water. In 1836 the lake was being inspected by the Ellesmere Canal Company once every six weeks. The earth dam topped by a dry stone wall was built sometime before 1870 and gives the lake a volume of 188,000m3/37? mg. The dam has a maximum length of 100 yds.

Rachel Leung, RCAHMW, 24 March 2010.

Sources:
Roberts, Geraint, The Lakes of Eryri, (Gwasg Carreg Gwalch, Llanrwst, 1995)
The National Archives, Kew, London, RAIL 826, The Ellesmere and Chester Canal Committee Minutes.