Clark Dam at Butler's Gorge, 1965 (AOT, PH30/1/9022)

There are 84 large dams (15 metres or more in height) in Tasmania and many hundreds of smaller ones. The earliest dams were built along the Hobart Rivulet from about 1809. They diverted the flow by race or pipe to water mills which produced flour, sawn timber and other products. These low weirs were often made from timber logs spiked together and sealed with clay, cheap structures with a limited life.

The first large dam in Tasmania was Lower Reservoir (18 metres high, earthfill) built in 1861 for Hobart's water supply. Upper Reservoir (also 18 metres, earthfill) followed in 1888 and Ridgeway (61 metres, concrete arch) in 1919. Glenorchy had its own water supply from Tolosa Dam (17 metres, earthfill) built in 1890 and Lime Kiln Gully Dam (26 metres, earthfill) in 1924. Dams for Queenstown and Burnie and the next dams for Hobart and Glenorchy came after the Second World War.

Tin mining in the north-east led to the construction of Frome Dam (18 metres, rockfill) near Pioneer in 1908 and Briseis Dam (24 metres, rockfill) near Derby in 1926. After the Briseis Dam disaster, in which the dam was washed away, it was rebuilt as Cascade Dam (27 metres, rockfill) in 1936. In 1918 the Mount Lyell Mining & Railway Company built Lake Margaret Dam (17 metres, concrete gravity) to supply electricity to the mine and Queenstown.

Starting with Miena Dam (27 metres, multiple arch) on the Great Lake in 1922, the government began 70-odd years of dam building to develop the state's hydro-electric resources. The Hydro-Electric Department and Commission built 43 large dams. Trevallyn Dam (33 metres, concrete gravity) in Launceston is a spectacular example when spilling. Cethana Dam (110 metres, rockfill) on the Forth River attracted international attention and its design has been copied in many countries. Gordon Dam (140 metres, concrete arch) in the south-west is the highest arch dam and has the largest storage in Australia.

Dams for irrigation began with the 4-metre high Tooms Lake Dam in 1840 to improve the reliability of the Macquarie River flow. Nearby the much more ambitious Long Marsh Dam was never finished. All the large irrigation dams have been built since 1960. The largest, Craigbourne Dam (24 metres, concrete gravity), was built in 1986 to supply farms in the Coal River valley.

Further reading: F Kinstler, 'Dams in Early Australia', Proceedings of the 9th national conference on engineering heritage, Ballarat, 1998; P Crawford & K Ryan, The history of the early water supply of Hobart, Hobart, [1988]; B Cole, Australia's 500 large dams, Melbourne, 2003.

Bruce Cole