Manly Dam

Manly Dam Reserve – also known as the Manly Warringah War Memorial Park – is an area of urban bushland in the Northern Beaches region of Sydney, Australia. Located among the suburbs of Allambie Heights, North Balgowlah, Frenchs Forest and Manly Vale in the Northern Beaches Council local government area.

The area of the reserve is 376 hectares, which includes the dam water surface area of approximately 30 hectares. The reserve adjoins the south-eastern edge of Garigal National Park.

The Northern Beaches area has long been recognised as being part of the traditional lands of the Kuringgai people. There are a number of Aboriginal heritage sites found within the Park.

The Reserve is centred on a lake known as Manly Dam that was formed by the construction of a dam across Curl Curl Creek

Curl Curl Creek was originally dammed in 1892 to create a reservoir with a capacity of 68.2 million imperial gallons (310 Ml) to provide a permanent supply of fresh water for the nearby village of Manly. The original 37 feet (11 m) high dam wall was subsequently raised in 1909, 1914 and 1922 to a final height of 115 feet (35 m), increasing the capacity to 441 million imperial gallons (2.00 Gl). However, as the population of the area grew, the dam's capacity became insufficient.

Water supply from Manly Dam had been augmented with supply from the main metropolitan system starting in 1906, initially from Mosman reservoir. By 1928 it was realised that Manly Dam had reached its limits and all future expansion would rely on the main metropolitan system. A trunk main was therefore laid from the Pymble reservoir and pumping from Manly Dam ceased in 1933. Briefly in 1942 after a period of drought, pumps were reinstalled and Manly Dam was brought back into service for nearly 10 months.

In the early 1990s engineers installed a large enclosed powered propeller against the dam wall on the reservoir side to prevent silt building up against the wall and causing damage to the structure. The propeller's purpose is also to prevent stratification of the water body, thereby improving the water quality by preventing eutrophication.

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Wikipedia