Dams and Reservoirs
3 min read
Dams and Reservoirs
An overall view of the Katse hydroelectric power plant dam in Lesotho, South Africa.
A characteristic feature of many hydroelectric power plants is the dam wall, which forms a kind of plug in the lowest part of the basin, retaining the water. Dams are commonly constructed from concrete, earth or rock, depending on the site conditions and type of dam. Masonry, steel and wood have also been used, particularly for older or smaller dams. The dam structure must be frequently checked for wear and damage. It is very important that a watertight connection between the dam and the bedrock and the sloped banks is maintained. Dams are generally equipped with outlet structures and spillways that allow the water level to be regulated and excess water to be safely discharged during floods. Large dams with substantial reservoirs are commonly associated with storage hydropower plants and may also serve other purposes.
Aside from generating energy from watercourses, dammed reservoirs can also serve as sources of drinking and irrigation water. Dams can provide flood protection and facilitate navigation.
18 pictures
18 pictures
Dam Types
Dams can be classified according to their construction and the way they resist water pressure. Major types include embankment, gravity, arch and buttress dams.
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Embankment dams
Embankment dams resist water pressure primarily by their weight. They are constructed mainly from compacted earth or rock and are generally classified as earthfill or rockfill dams.
The upstream face of a rockfill dam is usually protected by a watertight layer made of concrete, stone or steel plates or other waterproof materials. Many embankment dams contain a low-permeability core, often made of compacted clay, to limit water seepage. Earthfill dams are protected against surface erosion by suitable materials such as rock or concrete and require special spillways that can withstand erosive water currents.
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Concrete arch dams
Concrete arch dams are relatively thin structures firmly anchored into the steep sides of narrow valleys or canyons. Their curved shape transfers much of the water load into the rock abutments on either side.
15 pictures
15 pictures
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Concrete gravity dams
Concrete gravity dams are massive structures that resist water pressure primarily through their own weight. Their cross-section is roughly triangular, with a wide base and a narrow crest. The upstream face of a gravity dam is typically nearly vertical.
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Buttress dams
Made of reinforced concrete, these dams are supported by a series of buttresses on the downstream side. This design requires less concrete than a conventional gravity dam of comparable size.
10 pictures
10 pictures
