Lake Vyrnwy
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Lake Vyrnwy | ||
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Primary inflows River Vyrnwy and other small streams | | |
Primary outflows | River Vyrnwy | |
Managing agency | Hafren Dyfrdwy subsidiary of Severn Trent | |
Built | 1881–88 | |
Max. length | 7.64 kilometres (4.75 mi) | |
Max. width | 0.80 kilometres (0.5 mi) | |
Surface area | 4.54 square kilometres (1,121 acres) | |
Max. depth | 26 metres (84 ft) | |
Water volume | 59.7 gigalitres (13.125×10 9 imp gal) | |
Shore length1 | 19 kilometres (12 mi) | |
1 Shore length is not a well-defined measure. |
Lake Vyrnwy (Welsh: Llyn Efyrnwy, pronounced [ɛˈvərnʊɨ] or Llyn Llanwddyn) 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 (Welsh: Afon Efyrnwy) 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 (Welsh: Afon Efyrnwy) 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 26 metres (84 ft) deep, contains 59.7 gigalitres (13.125×10 9 imp gal), and covers an area of 4.54 square kilometres (1,121 acres),
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.
Climate
Climate data for Lake Vyrnwy No 2, Elevation: 360 m (1,181 ft), 1991–2020 normals | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
Mean daily maximum °C (°F) | 5.7 (42.3) |
6.0 (42.8) |
7.9 (46.2) |
10.7 (51.3) |
13.7 (56.7) |
16.3 (61.3) |
18.0 (64.4) |
17.5 (63.5) |
15.3 (59.5) |
11.7 (53.1) |
8.4 (47.1) |
6.3 (43.3) |
11.5 (52.6) |
Daily mean °C (°F) | 3.4 (38.1) |
3.5 (38.3) |
5.0 (41.0) |
7.1 (44.8) |
10.0 (50.0) |
12.7 (54.9) |
14.4 (57.9) |
14.2 (57.6) |
12.2 (54.0) |
9.1 (48.4) |
6.1 (43.0) |
4.0 (39.2) |
8.5 (47.3) |
Mean daily minimum °C (°F) | 1.2 (34.2) |
1.0 (33.8) |
2.0 (35.6) |
3.6 (38.5) |
6.2 (43.2) |
9.0 (48.2) |
10.9 (51.6) |
10.9 (51.6) |
9.1 (48.4) |
6.6 (43.9) |
3.8 (38.8) |
1.7 (35.1) |
5.5 (41.9) |
Average precipitation mm (inches) | 190.1 (7.48) |
162.5 (6.40) |
127.0 (5.00) |
96.8 (3.81) |
99.9 (3.93) |
98.6 (3.88) |
98.7 (3.89) |
110.4 (4.35) |
121.2 (4.77) |
179.9 (7.08) |
179.4 (7.06) |
214.5 (8.44) |
1,679 (66.09) |
Average precipitation days (≥ 1.0 mm) | 18.3 | 14.9 | 15.2 | 13.3 | 13.4 | 12.6 | 13.6 | 14.7 | 14.1 | 17.5 | 18.8 | 19.1 | 185.3 |
Source: Met Office[2] |
Construction
In 1879,
Thomas Hawksley was appointed as engineer-in-chief and prepared the design for a stone dam.[3] 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.[citation needed] The dam was the first large stone-built dam in the United Kingdom[citation needed] and cost £620,000 (equivalent to £70 million in 2019[4]).[citation needed] Earlier dams in Britain had been built using great earth embankments to hold back the water.[citation needed] In 1889, shortly after completion, the lake was stocked with 400,000 Loch Leven trout.
Between 1881 and 1892 the aqueducts carrying water to Liverpool were constructed.[citation needed]
Construction of the dam flooded the village of Llanwddyn. The residents of the village were not consulted about the proposal for a dam and opposed the plan. Their relocation involved the demolition of a church, two chapels, three inns, ten farmhouses, and 37 houses. A new settlement to house them was built lower down the valley by Liverpool Corporation.[5]
Description
The Vyrnwy dam is 44 metres (144 ft) high from the bottom of the valley, and 39 metres (128 ft) thick at the base; it is 358 metres (1,175 ft) long and has a road bridge running along the top. It is decorated with 31 arches each spanning 7.3 metres (24 ft) and two small towers each with four corner turrets rising 4.3 metres (14 ft) above the road surface. The dam was the first to be constructed with drainage tunnels designed to prevent a build up of pressure beneath the base. It is listed as a Grade I historic building by Cadw.[6][7]
The dam was the first to carry water over its crest instead of in a channel at the side. At the bottom of the dam is a body of water known as a stilling basin necessary to absorb the energy when the water flows over the crest and into the valley, and to stop the water eroding the foundations of the dam.
A power house located under the west tower contains an electrical generator driven by water leaving the reservoir. Before mains electricity arrived in the 1960s this was the area's only source of power.
About 1,200 metres (0.75 mi) from the dam is the reservoir's
The west and east towers release compensation water into the River Vyrnwy through huge valves; the river would dry up unless a minimum flow was maintained. Depending on the levels downstream, the reservoir can release from 25 to 45 Ml (5 to 10 million imp gal) of compensation water daily. The flow is measured by Natural Resources Wales at a weir a few hundred metres downstream.
Water supply
19th century
The water from Lake Vyrnwy is carried 109 kilometres (68 mi) in the Vyrnwy Large Diameter Trunk Main (LDTM) aqueduct which originally consisted of two pipelines, made largely of
The aqueducts cross the valley floor near
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.[8] in 1946, a fourth pipeline was added south of Oswestry to increase capacity to 227 million litres per day.[8]
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
21st century
In 2013, United Utilities commenced a major refurbishment of the entire 240 km (150 mi) of the LDTM aqueduct, which was scheduled for completion in 2020.[9] As of 2014 water provision relied on three parallel, 80 km long gravity pipelines, 1.1 metres (42 in) in diameter delivering up to 230,000 cubic metres (50×10 6 imp gal) per day into reservoirs at Prescot, east of Liverpool, which supplied customers in Cheshire and Merseyside.[10]
Nature reserve and conservation
Lake Vyrnwy is a designated
Around 90 species of bird have been recorded as breeding on the reserve, and six species of bat, including the
Managing the moorland helps improve the habitat for red grouse and the short-eared owl. Heather moorland which grows on the mountains around the lake is now[when?] being restored. In the past, heather was burnt, cut and the seeds collected to be sowed where the heather has gone. Burning at the Lake Vyrnwy moorland is no longer carried out, as the burning can have negative consequences for water management, namely water colouration.
Sheep, cattle and ponies also graze on the heather, managed by tenant farmers who farm the moorland in accordance with organic agriculture.
Broadleaf trees are being planted to replace
Tourism
Wood sculpture
Llanwddyn has had since 1995 a sculpture park in the valley below the dam, containing many wooden carved works. There are large wooden picnic benches in the shape of leaves and trees on the west side of the lake at Llechwedd Ddu. Near the old village on the beach is a sculpture of dolphins which, when the lake rises in a flood, appear to be jumping out of the water. Several totems are carved into standing trees and re-erected fallen trunks.[11]
Recreation
Activities in the area include sailing, hiking on
Tallest tree
The site was once home to the tallest tree in the UK, a
References
- ^ "Lake Vyrnwy". The Practical Engineer. V. Technical Publishing Company. 1891. Retrieved 11 June 2014.
- ^ "Lake Vyrnwy Climate". Met Office. Retrieved 25 April 2024.
- doi:10.1093/ref:odnb/12691. Retrieved 7 November 2017. (Subscription or UK public library membershiprequired.)
- Gross Domestic Product deflator figures follow the MeasuringWorth "consistent series" supplied in Thomas, Ryland; Williamson, Samuel H. (2018). "What Was the U.K. GDP Then?". MeasuringWorth. Retrieved 2 February 2020.
- ^ Hadfield, Charlotte (11 October 2020). "Remains of lost village hidden beneath reservoir used to supply Liverpool with drinking water". Liverpool Echo. Liverpool.
- ^ "Lake Vyrnwy Dam, Llanwddyn (32442)", Coflein, RCAHMW, retrieved 24 April 2021
- ^ Lake Vyrnwy Dam, British Listed Buildings, retrieved 24 April 2021
- ^ a b "Engineering Timelines - Vyrnwy Aqueduct (1892)". engineering-timelines.com. nd. Retrieved 3 November 2019.
- ^ "Vyrnwy water pipe works". United Utilities. Archived from the original on 18 August 2014. Retrieved 3 July 2013.
- ^ Harvey, Kevin (2014). "Vyrnwy Aqueduct Refurbishment" (PDF). WaterProjectsOnline.com. Archived from the original (PDF) on 3 November 2019.
- ^ "The Sculpture Park at Vyrnwy". Glyn-yr-Aur. Archived from the original on 22 February 2014. Retrieved 3 July 2013.
- ^ "Lake Vyrnwy". positivelynorthwales.com. 29 March 2016.
- ^ "Ex-tallest tree carved into hand". BBC News. 11 November 2011. Retrieved 27 July 2020.
- ^ "Neighbour inherits 'tallest tree' title". Archived from the original on 6 January 2014. Retrieved 15 March 2014.