| Marchlyn Mawr | |
|---|---|
 | |
  Marchlyn Mawr | |
| Location | Snowdonia, Wales |
| Coordinates | 53°8′12″N 4°4′9″W / 53.13667°N 4.06917°W |
| Type | reservoir, former natural lake |
| Basin countries | United Kingdom |
Marchlyn Mawr reservoir is a high level lake in Snowdonia behind Elidir Fawr mountain. It is used as the high level water source for Dinorwig power station, a closed-loop pumped storage hydroelectric generating facility.
It is said that nearby lies the cave containing Arthur's treasure,[citation needed] a source of bedazzlement to the wanderer who sees it, and of disaster to the pilferer who touches it. The lake itself lies in between two mountains Carnedd y Fillast and Elidir Fawr and lies at a height of 636m above sea level and the reservoir took four years to build (from 1975 to 1979). The reservoir holds about 9.2 million cubic metres (320 million cubic feet) of water. From the reservoir, a 10.5-metre (34 ft) diameter tunnel runs for 1.7 km (1.1 miles) to a 10 m (33 ft) diameter vertical shaft. From the bottom of the shaft, a 9.45 m (31 ft) diameter tunnel leads to the power station, 670 metres (2,200 ft) away.[1][2]
It is possible to cycle up the road to the reservoir[3] but a gate at the bottom prevents cars from driving on the road.
- ^ "First Hydro Analysts Conference, presentation 5" (PDF). Archived from the original (PDF) on 7 March 2014. Retrieved 8 April 2013.
- ^ SA Mathieson (16 May 2016). "Inside Electric Mountain: Britain's biggest rechargeable battery". The Register. Retrieved 27 June 2016.
- ^ Mitchell, Mathew (19 December 2019). "Climbing the Marchlyn Mawr Dam Road". ProCyclingUK.com. Retrieved 19 December 2019.