Blackwater Reservoir  The Blackwater Reservoir is a reservoir created behind a dam in the mountains above Kinlochleven, Lochaber, Highland, Scotland. At over 914 m long, the dam is the longest in the Highlands. The hydroelectric scheme was constructed in the early 1900s for the British Aluminium Company (later: British Alcan) for the purpose of smelting aluminium and was designed by engineers Patrick Meik and Charles Meik. Chief assistant resident engineer was William Halcrow. The dam, at 27 m high, was built at an elevation of over 305m in rugged and almost inaccessible terrain, and involved the construction of some 6 km of concrete aqueduct and nearly 13 km of steel pipe in total (four parallel pipelines). The dam was built using hand tools, without the benefit of mechanical earth moving machinery, and has been described as the last major creation of the traditional 'navvy' whose activities in the construction of canals and railways left an indelible mark on the British countryside. The power house and aluminium smelting plant were situated in Kinlochleven, which is adjacent to the sea loch Loch Leven. In recent years the smelting works has closed and has mostly been demolished albeit that a few buildings remain and have been given over to other uses, including a climbing wall which - unusually - has a refrigerated face so that people can practice ice climbing. The power station now produces electricity for the aluminium smelter in Fort William, supplementing the supply from the Lochaber hydroelectric scheme. Any surplus energy is sold to the national grid for public supply. Consequently, the dam, penstocks and other works associated with it remain in use. A number of workers lost their lives constructing the dam; their graves, which are marked by concrete markers, are close to the dam. During the First World War, German prisoners worked on laying a pipe down the hillside from the dam.