English: Top of Haweswater Dam. The construction of the dam to provide drinking water for Manchester was highly controversial, as it necessitated the drowning of two hamlets. The enabling legislation was passed in 1919, but construction was not commenced until 1930, with completion in 1940 although it took a further two years for the reservoir to fill completely. The dam (when the reservoir is full) raised the level of the existing lake by 29 metres, and extended the surface area of the lake to three times its previous size. Unusually a flume runs along the top of the dam, and unlike most dams there is no path across the top. Even if it was permitted, anyone attempting to pick their way along the top of the dam would need nerves of steel!