a few hundred metres downstream. Water supply 19th century The water from Lake Vyrnwy is carried in the Vyrnwy Large Diameter Trunk Main (LDTM) aqueduct which originally consisted of two pipelines, made largely of cast iron. To help maintenance work on the diameter cast-iron tunnel which took the aqueduct under the Mersey, riveted steel piping was also used, which was to become the norm for trunk water-main piping. The aqueducts cross the valley floor near Penybontfawr and then runs north of Llanrhaeadr-ym-Mochnant and Efail-rhyd on the north-east of the Tanat Valley. The aqueducts are largely underground although there are some visible surface features including air valves, the Cileos valve house, the Parc-uchaf balancing reservoirs, and a deep cutting to the west of Llanrhaeadr-ym-Mochnant. Brick and concrete-lined tunnels carried pipes at Hirnant, Cynynion and Llanforda, and a fourth was later added at Aber, so that the Hirnant tunnel could be made accessible for maintenance. 20th century From 1926 to 1938 the first section of a third pipeline was laid using bituminous-coated steel. in 1946, a fourth pipeline was added south of Oswestry to increase capacity to 227 million litres per day. In 1978–81, the pipe crossings beneath the Mersey and the Manchester Ship Canal were reorganised. After privatisation of the water companies, responsibility for the Vyrnwy Dam and associated structures fell to Severn Trent Water, and since 2018 to its subsidiary company Hafren Dyfrdwy. The rights to the water abstraction are with United Utilities for drinking water supply to Liverpool. 21st century In 2013, United Utilities commenced a major refurbishment of the entire of the LDTM aqueduct, which was scheduled for completion in 2020. As of 2014 water provision relied on three parallel, 80 km long gravity pipelines, in diameter delivering up to per day into reservoirs at Prescot, east of Liverpool, which supplied customers in Cheshire and Merseyside. Nature reserve and conservation Lake Vyrnwy is a designated Nature Reserve. The RSPB has several bird hides around the lake, where a number of rare species of birds are known to be breeding, including the peregrine falcon, the pied flycatcher, the common redstart, the Eurasian siskin and the wood warbler. Every spring they host a dawn chorus tour. Around 90 species of bird have been recorded as breeding on the reserve, and six species of bat, including the pipistrelle and brown long-eared bat. Butterfly species include purple hairstreaks, commas and peacocks. Dragonflies