The Upper Derwent

The Tarraleah Power Development was approved by the Tasmanian Parliament in 1934. It was seen as a way of both meeting future demands for electricity and helping to solve Tasmania's unemployment problem.

Early work on one of the Tarraleah canals

The area was largely inaccessible and the first task was to construct an access road. There were few machines and mechanical aids and living conditions were primitive.

A small weir with control gates was built at the southern end of Lake St Clair, raising its level by three metres and providing control over downstream flow. A pumping station was also constructed. The pumps had the ability to lower the level of the lake by six metres but were rarely used in recent years. They were removed from service in 1993.

Early work on the Tarraleah Power Development also involved the building of a small weir on the Derwent River at Butlers Gorge. Water flow in the river was diverted by the weir and sent some 25 kilometres overland in a combination of flume, canal and pipeline. It then dropped through steel penstocks, into the Tarraleah Power Station in the valley of the Nive River. Camps for construction workers were established at Tarraleah and Butlers Gorge as well as at five separate localities along the route of the overland channel. In 1938 the first three generators at Tarraleah were commissioned.

Clark Dam at Bulters Gorge

A further expansion of the scheme was hampered by serious labour shortages during the Second World War. The arrival of Polish and British migrants in 1947 allowed the completion of the 61-metre-high Clark Dam at Butlers Gorge in 1951. This created a second and larger storage for the development - Lake King William.

The small Butlers Gorge Power Station, with a capacity of 12.2 MW was constructed at the foot of the Clark Dam. The dam itself was raised a further six metres in 1964. A second overland channel between Lake King William and Tarraleah was completed in 1955. Extra water is diverted into it via an automatic pumping station on the Derwent River a few kilometres below the Clark Dam. Water is also diverted into the channel from three small tributaries of the Nive River. These works were completed in 1959.

The fourth, fifth and sixth generators at Tarraleah were commissioned in 1943, 1945 and 1951 respectively. All six operate with a head of about 290 metres and a total capacity of 90 MW.