Copeton Dam
Encyclopedia
Copeton Dam is a 113 metres high, earth and rock fill embankment dam
on the Gwydir River
near Inverell, New South Wales
, Australia
. The dam was built by the New South Wales Water Conservation & Irrigation Commission and the Department of Water Resources to supply water for irrigation. Construction commenced in 1968, was commissioned in 1973 and completed in 1976.
In 2007, it was decided the dam would need an upgrade for safety reasons. The A$70 million upgrade is expected to take 10 years to complete and involves the construction of a fuse plug
at Diamond Bay. Once the fuse plug is installed the dam wall will be raised and the spillway gate modified.
discharge channel was caused by rock failure under high in-situ compressive
stress. This type of erosion due to high in-situ stress has not been reported elsewhere in the world.
Remedial works involved building a training wall to separate the original single spillway into a service spillway and a secondary (emergency) spillway. A concrete slab, anchored to the underlying rock was constructed in the floor of the main scour channel to provide some additional protection on those rare occasions when the secondary spillway will discharge water over this area. The smaller, more frequent flood events will be discharged through the service spillway onto more scour resistant rock which has performed satisfactorily to date. The secondary spillway will operate very infrequently and will only discharge when the capacity of the service spillway is exceeded.
Geological investigations for the design of these remedial works included surface stress measurements in the unlined spillway discharge channel as well as geological mapping and diamond core drilling.
Embankment dam
An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof...
on the Gwydir River
Gwydir River
The Gwydir River is a large inland river in the northern part of the Australian state of New South Wales which is part of the Murray-Darling Basin. The river has two main tributaries—the Horton River and the Rocky River...
near Inverell, New South Wales
Inverell, New South Wales
Inverell is a town in northern New South Wales, Australia, situated on the Macintyre River. It is also the centre of Inverell Shire. Inverell is located on the Gwydir Highway on the western slopes of the Northern Tablelands. It has a temperate climate...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. The dam was built by the New South Wales Water Conservation & Irrigation Commission and the Department of Water Resources to supply water for irrigation. Construction commenced in 1968, was commissioned in 1973 and completed in 1976.
In 2007, it was decided the dam would need an upgrade for safety reasons. The A$70 million upgrade is expected to take 10 years to complete and involves the construction of a fuse plug
Fuse plug
A fuse plug is a collapsible dam installed on spillways in dams to increase the dam's capacity.The principle behind the fuse plug is that the majority of water that overflows a dam's spillway can be safely dammed except in high flood conditions. The fuse plug may be a sand-filled container, a...
at Diamond Bay. Once the fuse plug is installed the dam wall will be raised and the spillway gate modified.
Irrigation
Together with a series of diversionary weirs and regulatory works downstream from the dam, Copeton is able to provide a reliable flow of water to 30,000 ha of land. This amount is much less than the 50,000 ha originally planned because of higher rates of absorption and evaporation along some of the irrigation channels. Despite these over-estimates irrigated agriculture in the Gwydir Valley saw the area become Australia's major cotton producing region.Spillway
Unexpected erosion of hard, sound, unweathered granite in the unlined spillwaySpillway
A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...
discharge channel was caused by rock failure under high in-situ compressive
Compression member
A compression member is a general class of structural elements of which a column is the most common specific example.-Description:For a compression member, such as a column, the principal stress comes mainly from axial forces, that is forces that fall along one line, usually the centerline.The...
stress. This type of erosion due to high in-situ stress has not been reported elsewhere in the world.
Remedial works involved building a training wall to separate the original single spillway into a service spillway and a secondary (emergency) spillway. A concrete slab, anchored to the underlying rock was constructed in the floor of the main scour channel to provide some additional protection on those rare occasions when the secondary spillway will discharge water over this area. The smaller, more frequent flood events will be discharged through the service spillway onto more scour resistant rock which has performed satisfactorily to date. The secondary spillway will operate very infrequently and will only discharge when the capacity of the service spillway is exceeded.
Geological investigations for the design of these remedial works included surface stress measurements in the unlined spillway discharge channel as well as geological mapping and diamond core drilling.
See also
- Irrigation in AustraliaIrrigation in AustraliaIrrigation in Australia is a widespread practice to supplement low rainfall levels in Australia with water from other sources to assist in the production of crops or pasture. As the driest inhabited continent, irrigation is required in many areas for production of crops for domestic and export use...
- List of dams and reservoirs in Australia