A dam is a barrier structure constructed across a river or other water body to stop, divert, or control the flow of water. While dams are often built as part of hydroelectric power projects, their functions extend beyond electricity generation. The water stored in the reservoir behind a dam can also be used for irrigation, drinking water supply, flood control, and recreational purposes. In this article, we will discuss the different types of dams, classified based on their structure and use.
Types of dams
Types of dams based on structure
Gravity dams
A gravity dam, as the name suggests, relies on its own weight to resist the horizontal pressure of water. These dams are usually constructed from concrete or masonry, which is heavy enough to withstand external forces. Gravity dams can be built in a variety of locations, provided that proper engineering calculations are carried out and the foundation consists of strong, stable bedrock.
Arch dams
Arch dams are curved structures with the convex side facing the upstream reservoir. The curvature allows water pressure to be transferred laterally to the abutments (the valley walls), which absorb most of the load. In fact, the water pressure itself helps to strengthen the structure by pressing the arch firmly against the abutments.
These dams are typically built of concrete or masonry and are most suitable for narrow, steep-sided canyons or valleys with strong rock foundations. In cases where a single arch is not sufficient, multiple arches supported by buttresses may be used to cover a larger span.
Embankment dams
Embankment dams are constructed using natural materials, usually obtained from areas close to the construction site. They typically consist of an impervious core, which prevents water seepage, and a semi-pervious outer shell that provides stability and support.
When an embankment dam is built mainly with soil, clay, or alluvial material, it is called an earth-fill dam. On the other hand, if it is primarily made from rocks, stones, or other granular material, it is called a rock-fill dam.
Buttress dams
A buttress is a structural support built to strengthen or reinforce another structure. A buttress dam consists of a relatively thin concrete wall on the upstream (reservoir) side, which is supported at intervals by buttresses on the downstream side. These buttresses transfer the water pressure from the wall to the foundation, allowing the dam to resist large forces while using less construction material compared to a gravity dam.
Types of dams based on use
Storage dams
Storage dams are the most common type of dams. Their primary purpose is to store excess water in reservoirs during periods of high flow, such as the rainy season. The stored water can then be used later for irrigation, domestic supply, industrial needs, and hydroelectric power generation. In addition to water supply, storage dams also help reduce the risk of floods by regulating river flow and releasing water in a controlled manner.
Diversion dams
Diversion dams, as the name suggests, are built to divert the flow of a river into canals, tunnels, or pipelines. The diverted water is typically used for irrigation, supplying inland areas with a steady water source.
Apart from irrigation, diversion dams are also important in hydropower projects. In river-diversion or run-of-the-river power plants, a portion of the river is diverted through a tunnel or pipeline, where it passes through turbines to generate electricity before being returned to the main river channel.
Detention dams
Detention dams are primarily constructed for flood control and for regulating river flow in flood-prone areas. Unlike storage dams, they are not designed to retain water permanently. Instead, they temporarily hold back excess floodwater and then release it at a controlled rate. This gradual release helps maintain a steady flow downstream, reducing the risk of flash floods and damage to surrounding areas.
Cofferdams
Cofferdams are temporary dams built to create a dry working environment during the construction or repair of structures in or near water, such as bridges, piers, or underwater pipelines. A cofferdam is essentially a watertight enclosure constructed within a water body. Once the enclosure is in place, water is pumped out to expose the riverbed or seabed, allowing construction activities to be carried out safely and efficiently.
Advantages and disadvantages of Dams
Advantages of dams
- Dams play a key role in hydroelectric projects, producing electricity from hydropower, which is a clean and renewable energy resource. Hydropower is one of the most established and widely developed alternatives to fossil fuels.
- 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 submerged in reservoirs decomposes and releases greenhouse gases. However, these emissions are relatively small compared to those from fossil fuels. Additionally, constructing a reservoir often requires cutting down large numbers of trees.
- Dams reservoirs may affect the quality of water in the river. The salinity of the river may increases overtime.
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Very informative post covering all of the different types of dam in the world. Not many people know the names of the different types nor any information about them really, so thank you for this post raising more awareness.
Thank you