A dam is a barrier structure constructed to stop, divert or control the flow of a river (or other water bodies). Primarily, dams are constructed as a part of a hydroelectric power project. The water impounded by the dam in a reservoir is used for the generation of electricity in the future. This water stored in the dam reservoirs is also used for irrigation and drinking purposes. In this article, we will discuss the different dam types classified based on their structure and use.
The different dam types
Dam types based on the structure
Gravity dam as the name suggests uses gravity to resist the horizontal pressure of water. These are made of concrete or masonry which is heavy enough to resist external forces. Gravity dams can be constructed in any geographical location as long as calculations are done right and the foundation bedrock is strong enough.
Embankment dams are made from materials obtained nearby construction site. These dams have an impervious core and a semi impervious outer structure which supports the core. If the embankment dam is constructed mainly from the soil, clay, and alluvial material, it is termed an earth-filled dam. If the embankment dam is mainly made from rocks, stones, and other granular material, it is termed a rock-filled embankment dam.
These dams are constructed in the shape of an arch with bulging curvature facing the upstream reservoir. The pressure of water is absorbed mainly by the abutments. The water pressure pushes the arch strengthening the dam.
Arch dams are built with concrete or masonry and are most suitable for narrow canyons and valleys. Large length dams may have multiple arches and buttresses.
A buttress is a structure built to provide support to other structures. Buttress dams have a solid concrete wall on the reservoir side which is supported by the buttresses on the downstream side.
Dam types based on the use
Storage dams are the most common types of dams. They are used to store water in reservoirs during the rainy season. The water stored is used for irrigation, household use, and often for electricity production. These dams lower the risk of flooding in the areas downstream of the river.
These dams as the name suggests are used to divert the river water to a canal. The canal goes deep in the inland areas and provides water for irrigation.
Diversion dams are also used for electricity generation in river-diversion power plants. A portion of the river is diverted to a tunnel or a pipeline by a diversion dam. Generators placed in the tunnel produce electricity and the water is channeled back into the main stream.
Detention dams are used for flood control or managing the flow of a river. They are built in flood-prone areas. The water from the detention dams is released at a slow controlled rate so as to maintain a constant flow of the river downstream.
These dams are built while constructing a structure above or below a water body such as bridges or underwater pipelines. A cofferdam is an enclosure constructed within a water body that is made watertight and dried out with the help of pumps.
Advantages and disadvantages of Dams
Advantages of dams
- Dams are part of hydroelectric projects which produce electricity using hydropower which is a renewable resource. Hydropower is the most researched and developed alternative to fossil fuels nowadays.
- Dams reservoirs provide water for drinking, irrigation and other household uses.
- Dams are used to divert water into canals which can reach the drier regions.
- Dams are used for flood control and managing the flow of a river.
Disadvantages of dams
- Dams blocks the natural flow of a river which can badly affect the fish species.
- The organic matter under the water in reservoirs decomposes to produce green house gases. Though, this emission is not as large as that from fossil fuels. Moreover, a lot of trees may be cut while constructing a reservoir.
- Dams reservoirs may affect the quality of water in the river. The salinity of the river may increases overtime.