Lake Vyrnwy (, or ) is a reservoir in Powys, Wales, built in the 1880s for Liverpool Corporation Waterworks to supply Liverpool with fresh water. It flooded the head of the Vyrnwy () valley and submerged the village of Llanwddyn. The Lake Vyrnwy Nature Reserve and Estate that surrounds the lake is jointly managed by the Royal Society for the Protection of Birds (RSPB) and Hafren Dyfrdwy and is a popular destination for ornithologists, cyclists and hikers. The reserve is designated as a national nature reserve, a Site of Special Scientific Interest, a Special Protection Area, and a Special Area of Conservation. Geography Lake Vyrnwy is a reservoir in Powys, Wales, created in 1888 by flooding the head of the river Vyrnwy () valley. The river flows from the dam into Shropshire where it converges with the River Severn near the village of Melverley on the Welsh border and outflows into the Bristol Channel. When the reservoir is full, it is deep, contains , and covers an area of , the equivalent of around 600 football pitches. The lake has a perimeter of with a road that goes all the way around it. Its length is . 311 brooks, waterfalls and rivers flow into the lake and are named after the mountains or hillsides they flow from. The main ones, clockwise from the west side of the dam, are named Afon Hirddu, Eunant, Afon Eiddew, Afon Naedroedd, Afon Cedig and Afon Y Dolau Gwynionew. On the northern edge of the lake is a small hamlet called Rhiwargor where the rivers Afon Eiddew and Afon Naedroedd meet. Up the valley of Afon Eiddew is a waterfall known locally as Pistyll Rhyd-y-meincau, commonly known as Rhiwargor waterfall. Construction In 1879, George Deacon was instructed to prepare the parliamentary plans for the Vyrnwy Dam. The valley was chosen because of its size, favourable geology and its source, the River Vyrnwy, having a large water catchment area. Thomas Hawksley was appointed as engineer-in-chief and prepared the design for a stone dam. Dam construction with great blocks of Welsh slate started in 1881 and was completed in 1888. Hawksley resigned in 1885 because of a conflict with George Deacon who was appointed as joint engineer. The dam was the first large stone-built dam in the United Kingdom and cost £620,000 (equivalent to £ million in ). Earlier dams in Britain had been built using great