The Blackwater Reservoir is a reservoir created behind a dam in the mountains above Kinlochleven, Lochaber, Highland, Scotland. The dam is 914 m long, the longest in the Highlands. The hydroelectric scheme was constructed in the early 1900s for the British Aluminium Company for the purpose of smelting aluminium and was designed by engineers Patrick Meik and Charles Meik. Chief assistant resident engineer was William Halcrow. The 27 m high dam was built at an elevation of about 305m in rugged terrain. 6 km of concrete aqueduct was constructed, and nearly 13 km of steel pipe was laid (six 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'. The power house and aluminium smelting plant were situated in Kinlochleven, which is adjacent to the sea loch Loch Leven. The power station now produces electricity for the aluminium smelter in Fort William, supplementing the supply from the Lochaber hydroelectric scheme. Surplus energy is sold to the national grid for public supply. 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.