The Crotty Dam, also known during construction as the King Dam, or the King River Dam on initial approval, is a rockfill

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface ...

with a controlled and uncontrolled spillway across the King River, between Mount Jukes and Mount Huxley, located in

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

, Australia. The impounded

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

is called

Lake Burbury Lake Burbury is a man-made water reservoir created by the Crotty Dam inundating the upper King River valley that lies east of the West Coast Range. Discharge from the reservoir feeds the John Butters Hydroelectric Power Station, owned and ...

. The dam was constructed in 1991 as part of the King River Power Development Scheme, by the

Hydro Electric Commission Hydro Tasmania, formerly the Hydro-Electric Commission (HEC), is a Tasmanian Government business enterprise which is the main electricity generator in Tasmania, Australia. Originally oriented towards hydro-electricity, owing to Tasmania's dr ...

for the purpose of generating

hydro-electric power Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other renewable sources combined and also ...

via the John Butters Power Station located below the dam wall.

Features and location

The Crotty Dam, together with the Darwin Dam, are two major dams that form the headwaters for the King River Hydroelectric Power Development. The dam is located in the upper reaches of the King River gorge where the river breaks through the

West Coast Range The West Coast Range is a mountain range located in the West Coast, Tasmania, West Coast region of Tasmania, Australia. The range lies to the west and north of the main parts of the Franklin-Gordon Wild Rivers National Park. The range has h ...

. It captures the high rainfall in the catchment of the King River and allows diversion of water through a tunnel to the John Butters Power Station downstream of the dam. The Crotty Dam wall, constructed with of concrete faced rock and gravel fill core, is high and long. At 100% capacity the dam wall holds back (43,000×106 cu ft) of water. The surface area of Lake Burbury is and the catchment area is . The single uncontrolled and controlled spillway is capable of discharging .

Spillway

A unique feature of the dam is its spillway. The spillway is located on the embankment, rather than on one of the rock abutments. This had never been successfully attempted before in the design of dams of any significant height, due to problems in making allowance for embankment settlements. In the case of Crotty Dam, the embankment was partly composed of well graded gravels, and thus a very high modulus of embankment deformation was achieved. The high modulus limits embankment settlements. Additionally, the spillway was designed to articulate in order to accommodate any settlement that ''did'' occur. The spillway is designed to allow sufficient time for a large jet flow valve located in the diversion tunnel to be opened so that larger floods can be safely handled. The spillway designers, Sergio Giudici, also the chief engineer on the

Gordon Dam The Gordon Dam, also known as the Gordon River Dam, is a major gated double curvature concrete arch dam with a controlled Spillway#Types, spillway across the Gordon River, located in Southwest National Park, Tasmania, Australia. The impounded r ...

, Frank Kinstler, Steven Li, Tony Morse and Graeme Maher were acknowledged within the engineering community because the spillway was the first known to provide for articulation of the spillway structure so that movements in its foundations could occur without damage to the overlying structure.

Power station

The water from Lake Burbury is conveyed through a long unlined tunnel that runs through Mount Jukes to the John Butters Power Station, which is located on the King River downstream of the dam and King River gorge, near the confluence with the Queen River.

History

The dam was constructed in the 1980s following the abandonment of the Gordon-below-Franklin power development scheme, part of the

Franklin Dam The Gordon-below-Franklin Dam (or simply Franklin Dam) project was a proposed dam on the Gordon River in Tasmania, Australia, that was never constructed. The movement that eventually led to the project's cancellation became one of the most sign ...

. The Crotty Dam was commissioned in 1991, with the King River Power development being completed by 1992. The dam is named in honour of James Crotty who founded the North Mount Lyell Copper Mine at the turn of the 20th century. A ghost town site of the same name Crotty was submerged by the waters of Lake Burbury. In the 1910s the

Mount Lyell Mining & Railway Company Mount Lyell Mining and Railway Company was a Tasmanian mining company formed on 29 March 1893, most commonly referred to as ''Mount Lyell''. Mount Lyell was the dominant copper mining company of the West Coast, Tasmania, West Coast from 1893 to 1 ...

had investigated and surveyed a site very close to this dam for a proposed hydro electric scheme.

Charles Whitham Charles Whitham was an Australian writer. He wrote the oft-reprinted ''Western Tasmania: A land of Riches and Beauty'', which was a comprehensive study of the geographical features of West Coast, Tasmania and the conditions of the region in the ...

also wrote of the inevitability of the dam in 1927 and even proposed "Lake Dorothy" as a name for the reservoir. In 2001,

Engineers Australia Engineers Australia (EA), known formally as the Institution of Engineers, Australia, is an Australian professional body and Non-profit organization, not-for-profit organisation whose purpose is to advance the science and practice of engineerin ...

selected Crotty Dam as one of the 25 dams with the greatest Australian heritage value. It was awarded a Historic Engineering Marker as part of the Engineering Heritage Recognition Program.

References

External links

King Catchment

Hydro Tasmania Hydro Tasmania, formerly the Hydro-Electric Commission (HEC), is a Tasmanian Government business enterprise which is the main electricity generator in Tasmania, Australia. Originally oriented towards hydro-electricity, owing to Tasmania's dr ...