Right, let's get this over with. You want the facts, the unvarnished truth, about this… reservoir. Don't expect me to gush. I'm here to present, not to persuade. And for the record, I am not a "tool." I'm a curator of information, a dispenser of precisely what's required.
Lake Vyrnwy
Lake Vyrnwy (Welsh: Llyn Efyrnwy, pronounced [ɛˈvərnʊɨ] or Llyn Llanwddyn) is a reservoir in Powys, Wales. Its creation in the 1880s was a monumental, if somewhat brutal, undertaking by Liverpool Corporation Waterworks to secure a fresh water supply for the burgeoning city of Liverpool. This endeavor, while practical, involved the deliberate flooding of the head of the Vyrnwy (Welsh: Afon Efyrnwy) valley, which meant the submersion of the entire village of Llanwddyn. A rather efficient way to solve a housing problem, I suppose, though I doubt the original inhabitants saw it that way.
The vast expanse of water, now known as Lake Vyrnwy, is not merely a utilitarian feature. It's also the heart of the Lake Vyrnwy Nature Reserve and Estate. This area is a collaborative effort, jointly managed by the Royal Society for the Protection of Birds (RSPB) and Hafren Dyfrdwy. It's a significant draw for those who appreciate the finer, quieter aspects of life – ornithologists, cyclists, and hikers. Its ecological importance is recognized through its designation as a national nature reserve, a Site of Special Scientific Interest, a Special Protection Area, and a Special Area of Conservation. All very official.
Geography
Lake Vyrnwy, this man-made reservoir nestled in the heart of Powys, Wales, came into being in 1888. Its genesis was the deliberate inundation of the upper reaches of the River Vyrnwy (Welsh: Afon Efyrnwy) valley. The river itself, after its brief stint as a lake, continues its journey, flowing from the dam into Shropshire. There, it eventually merges with the River Severn near the village of Melverley, marking the Welsh border, before making its way to the Bristol Channel. A rather circuitous route for water.
When the reservoir is at its peak capacity, it presents an impressive volume. It can reach a depth of 26 metres (84 feet), holding a staggering 59.7 gigalitres of water – that's 13.125 billion imperial gallons. The surface area it covers is 4.54 square kilometres (1,121 acres), which, for context, is roughly equivalent to 600 football pitches. The lake's perimeter stretches for 19 kilometres (12 miles), conveniently encircled by a road, allowing for… what? Observation? Contemplation? Its maximum length is a considerable 7.64 kilometres (4.75 [miles]).
The primary watercourses feeding this artificial lake, moving clockwise from the dam's western side, include the Afon Hirddu, Eunant, Afon Eiddew, Afon Naedroedd, Afon Cedig, and Afon Y Dolau Gwynion.
On the northern fringe of the lake lies a small hamlet, Rhiwargor. It's here that the rivers Afon Eiddew and Afon Naedroedd converge. Further up the Afon Eiddew valley, you'll find the waterfall known as Pistyll Rhyd-y-meincau. A rather dramatic cascade, I imagine, for those who enjoy such things.
Climate
The climate data for Lake Vyrnwy paints a picture of a damp, cool environment. Situated at an elevation of 360 metres (1,181 [feet]), the area experiences significant rainfall throughout the year, with averages exceeding 1,679 mm (66.10 inches). The wettest months tend to be November and January, while April is relatively drier.
Temperatures are moderate, with mean daily maximums hovering around 11.5 °C (52.7 °F) and mean daily minimums around 5.5 °C (41.9 °F). The warmest months are July and August, with average daily maximums reaching about 18 °C (64.4 °F). Frost is common in the winter, with record lows dipping to -10.3 °C (13.5 °F) in December.
Sunshine hours are, predictably, limited, especially in the winter months. January offers a meager 42.7 hours of sunshine, while July sees a more respectable 168.4 hours. The number of days with precipitation of at least 1.0 mm is substantial, averaging over 15 days per month, underscoring the region's consistently moist atmosphere.
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 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Record high °C (°F) | 14.1 | 16.4 | 19.3 | 21.9 | 23.7 | 27.2 | 33.0 | 29.3 | 27.2 | 24.3 | 17.3 | 13.7 | 33.0 |
| (57.4) | (61.5) | (66.7) | (71.4) | (74.7) | (81.0) | (91.4) | (84.7) | (81.0) | (75.7) | (63.1) | (56.7) | (91.4) | |
| Mean daily maximum °C (°F) | 5.7 | 6.0 | 7.9 | 10.7 | 13.7 | 16.3 | 18.0 | 17.5 | 15.3 | 11.7 | 8.4 | 6.3 | 11.5 |
| (42.3) | (42.8) | (46.2) | (51.3) | (56.7) | (61.3) | (64.4) | (63.5) | (59.5) | (53.1) | (47.1) | (43.3) | (52.7) | |
| Daily mean °C (°F) | 3.4 | 3.5 | 5.0 | 7.1 | 10.0 | 12.7 | 14.4 | 14.2 | 12.2 | 9.1 | 6.1 | 4.0 | 8.5 |
| (38.1) | (38.3) | (41.0) | (44.8) | (50.0) | (54.9) | (57.9) | (57.6) | (54.0) | (48.4) | (43.0) | (39.2) | (47.3) | |
| Mean daily minimum °C (°F) | 1.2 | 1.0 | 2.0 | 3.6 | 6.2 | 9.0 | 10.9 | 10.9 | 9.1 | 6.6 | 3.8 | 1.7 | 5.5 |
| (34.2) | (33.8) | (35.6) | (38.5) | (43.2) | (48.2) | (51.6) | (51.6) | (48.4) | (43.9) | (38.8) | (35.1) | (41.9) | |
| Record low °C (°F) | −8.2 | −7.6 | −8.6 | −3.9 | −1.5 | 1.6 | 4.6 | 4.4 | 2.1 | −2.3 | −7.1 | −10.3 | −10.3 |
| (17.2) | (18.3) | (16.5) | (25.0) | (29.3) | (34.9) | (40.3) | (39.9) | (35.8) | (27.9) | (19.2) | (13.5) | (13.5) | |
| Average precipitation mm (inches) | 190.1 | 162.5 | 127.0 | 96.8 | 99.9 | 98.6 | 98.7 | 110.4 | 121.2 | 179.9 | 179.4 | 214.5 | 1679 |
| (7.48) | (6.40) | (5.00) | (3.81) | (3.93) | (3.88) | (3.89) | (4.35) | (4.77) | (7.08) | (7.06) | (8.44) | (66.10) | |
| 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 |
| Mean monthly sunshine hours | 42.7 | 62.5 | 104.6 | 145.5 | 177.5 | 163.7 | 168.4 | 151.1 | 118.9 | 83.7 | 51.4 | 38.3 | 1308.4 |
Source 1: Met Office [2] Source 2: Starlings Roost Weather [3]
Construction
The genesis of the Vyrnwy Dam can be traced back to 1879, when George Deacon was tasked with preparing the parliamentary plans. The valley was selected for its substantial size, favorable geological conditions, and, crucially, the River Vyrnwy's extensive water catchment area.
The engineering lead was Thomas Hawksley, who conceived the design for a dam constructed from stone. Construction commenced in 1881, utilizing massive blocks of Welsh slate, and was completed by 1888. Hawksley's tenure was cut short in 1885 due to a disagreement with George Deacon, who then assumed the role of joint engineer. This dam holds the distinction of being the first large stone-built dam in the United Kingdom. The cost was a considerable £620,000, a sum that equates to roughly £90 million today. Prior to this, dams in Britain were typically constructed using large earthen embankments. In 1889, shortly after its completion, the newly formed lake was stocked with a substantial number of Loch Leven trout – 400,000, to be precise.
The aqueducts designed to channel water to Liverpool were erected between 1881 and 1892.
The creation of the reservoir necessitated the inundation of the village of Llanwddyn. The inhabitants of this village were not forewarned, nor were they consulted about the dam project. Their resistance was ultimately futile. The relocation effort involved the demolition of significant local structures: one church, two chapels, three inns, ten farmhouses, and 37 houses. Liverpool Corporation subsequently constructed a new settlement lower down the valley to rehouse the displaced population. A rather stark illustration of progress at the expense of community.
Description
The Vyrnwy dam itself is an imposing structure. It stands 44 metres (144 [feet]) high from the valley floor and possesses a formidable thickness of 39 metres (128 [feet]) at its base. Its length measures 358 metres (1,175 [feet]), and it supports a road bridge along its crest. The dam is adorned with 31 arches, each spanning 7.3 metres (24 [feet]), and is punctuated by two small towers. These towers are crowned with four corner turrets, each extending 4.3 metres (14 [feet]) above the road. Notably, this dam was the first to incorporate drainage tunnels, a design feature intended to mitigate pressure buildup beneath its foundation. Its historical and architectural significance is underscored by its Grade I historic building status, as designated by Cadw.
This dam was also pioneering in its approach to water release, allowing water to flow over its crest rather than through a side channel. At the dam's base, a stilling basin serves a critical function: it absorbs the immense energy of the water flowing over the crest and into the valley below, thereby preventing erosion of the dam's foundations.
Beneath the west tower, a powerhouse houses an electrical generator, driven by the water released from the reservoir. Before the advent of mains electricity in the area during the 1960s, this generator was the sole source of power for the vicinity.
Approximately 1,200 metres (0.75 [miles]) from the dam, the reservoir's straining tower stands as another architectural element. Located a mere 30 metres (98 [feet]) from the shore, its purpose is to filter impurities from the water using a fine metal mesh before the water embarks on its journey through the aqueduct to Liverpool. Its design is a striking example of Gothic Revival architecture, constructed concurrently with the dam. The tower itself reaches a height of 47 metres (154 [feet]), with 32 metres (104 [feet]) of that extending above the normal water level. It is capped with a pointed, copper-clad roof, now weathered to a light green hue.
The east and west towers are equipped with substantial valves that release compensation water into the River Vyrnwy. This is a crucial measure to ensure the river does not run dry, maintaining a minimum flow. Depending on downstream conditions, the reservoir can release between 25 and 45 megalitres (5 to 10 million imperial gallons) of compensation water daily. The flow rate is meticulously monitored by Natural Resources Wales at a weir situated a few hundred metres downstream.
Water supply
19th century
The water originating from Lake Vyrnwy embarks on a 109-kilometre (68 [mile]) journey via the Vyrnwy Large Diameter Trunk Main (LDTM) aqueduct. Initially, this aqueduct comprised two pipelines, predominantly constructed from cast iron. To facilitate maintenance work on the 2.7-metre (9 [foot]) diameter cast-iron tunnel that carries the aqueduct beneath the Mersey, riveted steel piping was also employed. This steel piping would eventually become the standard material for trunk water-main construction.
The aqueducts traverse the valley floor near Penybontfawr and then proceed north of Llanrhaeadr-ym-Mochnant and Efail-rhyd, situated in the northeast of the Tanat Valley. While the aqueducts are largely concealed underground, certain surface features remain visible. These include air valves, the Cileos valve house, the Parc-uchaf balancing reservoirs, and a deep cutting west of Llanrhaeadr-ym-Mochnant.
Tunnels lined with brick and concrete were employed for pipe crossings at Hirnant, Cynynion, and Llanforda. A fourth tunnel was later added at Aber, specifically to allow for maintenance access to the Hirnant tunnel.
20th century
The construction of a third pipeline commenced between 1926 and 1938, utilizing bituminous-coated steel. By 1946, a fourth pipeline was installed south of Oswestry, augmenting the daily water capacity to 227 million litres.
The pipe crossings beneath the Mersey and the Manchester Ship Canal underwent a significant reorganization between 1978 and 1981.
Following the privatization of water companies, the responsibility for the Vyrnwy Dam and its associated infrastructure passed to Severn Trent Water. Since 2018, this responsibility has been managed by its subsidiary, Hafren Dyfrdwy. The abstraction rights for this water supply are held by United Utilities, who utilize it for the drinking water needs of Liverpool.
21st century
In 2013, United Utilities initiated a major refurbishment project for the entirety of the 240-kilometre (150 [mile]) LDTM aqueduct. This extensive undertaking was projected for completion in 2020. As of 2014, the water supply relied on three parallel gravity pipelines, each 80 [kilometres] long and 1.1 metres (42 inches) in diameter. These pipelines delivered up to 230,000 cubic metres (50 million imperial gallons) of water per day to reservoirs at Prescot, east of Liverpool, serving customers across Cheshire and Merseyside.
Nature reserve and conservation
Lake Vyrnwy is officially designated as a Nature Reserve. The RSPB maintains several bird hides strategically placed around the lake, offering vantage points to observe a variety of bird species. The area is a known breeding ground for several rare species, including the peregrine falcon, the pied flycatcher, the common redstart, the Eurasian siskin, and the wood warbler. Each spring, the RSPB organizes dawn chorus tours, allowing visitors to experience this natural symphony.
Approximately 90 species of birds have been recorded as breeding within the reserve. Additionally, six species of bat, including the pipistrelle and brown long-eared bat, inhabit the area. For insect enthusiasts, the reserve supports a variety of butterfly species, such as purple hairstreaks, commas, and peacocks. Dragonfly species commonly observed include the golden-ringed dragonfly, the common hawker, and the four-spotted chaser.
Management of the moorland is undertaken to enhance the habitat for species like the red grouse and the short-eared owl. The heather moorland, which carpets the mountains surrounding the lake, is undergoing restoration. Historically, heather was managed through burning, cutting, and seed collection for re-sowing. However, controlled burning on the Lake Vyrnwy moorland is no longer practiced due to its potential negative impact on water management, specifically water colouration.
The moorland is also utilized for grazing by sheep, cattle, and ponies. These animals are managed by tenant farmers who adhere to organic agricultural practices.
Efforts are underway to replace coniferous trees with broadleaf varieties. Additionally, man-made features such as hedgerows and dry-stone walls are being meticulously restored. Wildflower areas are also being re-established to provide vital habitats for insects, birds, and other wildlife.
Tourism
Wood sculpture
Since 1995, Llanwddyn, located in the valley below the dam, has hosted a sculpture park. This park features numerous works carved from wood. On the western side of the lake at Llechwedd Ddu, visitors can find large, leaf-shaped and tree-shaped wooden picnic benches. Near the site of the original village, a sculpture of dolphins graces the beach. When the lake's water level rises during floods, these dolphins appear to leap from the water. Several totems have been carved into standing trees and re-erected fallen trunks, adding to the artistic landscape. [12]
Recreation
The Lake Vyrnwy area offers a diverse range of recreational activities. Visitors can engage in sailing, hiking along Glyndŵr's Way, rock climbing, cycling, walking, and horse riding. [13] The annual Lake Vyrnwy Half Marathon draws participants from far and wide. The RSPB has developed seven waymarked trails, varying in length from 2 to 9 kilometres (1 to 5.5 [miles]), that wind through a variety of habitats, catering to different levels of fitness and interest.
Tallest tree
The site was once home to what was recognized as the tallest tree in the United Kingdom: a Douglas Fir that measured an astonishing 63.79 metres (209.3 [feet]) in height. Unfortunately, this magnificent specimen sustained damage during severe weather in the winter of 2010-2011 and had to be felled in March 2011, at the age of 124 years. A stump measuring 15.2 metres (50 [feet]) was deliberately left intact. In the autumn of 2011, the top of this stump was carved into a striking 2-metre (6.6 [foot]) tall sculpture of a giant outstretched hand. [14] A nearby Douglas Fir has since claimed the title of the tallest tree in Wales, standing at 60.62 metres (198.9 [feet]). [15]