Water dams are found in different parts of the world and they are constructed for various uses, some dams are small while others could be as large as a river. The immediate temperature within an area are modified because of the presence of a dam, an area that has dam near it tends to be colder than areas that are far apart. A dam could also serve as an ecosystem that accommodates few numbers of living organisms, and could be used for local fishing and boating.

What is a dam?

Picture of a dam

A dam is a constructed barrier used for limiting water flow and in turn raises the level of water; it is usually built to serve as a reservoir for water storage and for generating electricity. A wall is usually built around a dam to prevent overflow of water and flooding within an area. Most dams are built close to a river or stream and may serve a as storage that provides water for different purposes. One of the uses of dam is for recreational activity such as swimming. Many people normally go to the dam to relax by the bank, due to its quietness and the chill air it sends to the immediate environment, however some dams could be as deep as 200 ft depending on the use; such depth could be very dangerous for an inexperienced swimmer.

Types of dams

Dams are basically classified based their purpose, such dams include

1. Storage dam– this is constructed to prevent the overflow of water especially when there is a large flow of water from the river, storage dam usually stores water so that it can be used during dry season. This water is particularly used for irrigation, hydro-power supply and for domestic water supply etc.
2. Diversion dam:A diversion dam is a dam constructed for diverting water from the river and then channeling it into irrigation canal (or a conduit); it has a low height with a small storage reservoir. This dam has a sufficient pressure for pushing water into ditches, canals, or other conveyance system and it is used for irrigation, and for diversion from a stream to a distant storage reservoir.
3. Coffer dam- a coffer dam is a temporary enclosure constructed around an on-going construction site to keep flowing water away, so that the construction can be carried out in a dry ground. This dam is usually constructed on the upstream of an existing dam, to divert water into a diversion tunnel during the construction process of the dam.
4. Detention dam– this is constructed to control flood; this dam retards the flow in the river on its downstream during floods by storing some floodwater thereby, reducing the effect of sudden flood. The water retained in the reservoir is later released in a gradual process based on the carrying capacity of the channel downstream of the detention dam. This construction is done to protect the entire region of the downstream on the side of the dam from possible damage, due to floods. Detention dam may be used as a storage dam.
5. Debris dam:Debris dam is usually constructed to catch and filter debris such as sand, gravel, and drift wood flowing in the river together with water. This usually leave the river clean and clear after collecting all the debris.
6. Gravity dam– is a dam constructed from concrete or stone masonry and it is designed to hold backwater by primarily utilizing the weight of the material alone to resist the horizontal pressure of water pushing against it. Gravity dam is constructed in such way that each section of the dam is stable and able to hold back large volumes of water. Gravity essentially holds the dam down to the ground, preventing water from pushing it over. Gravity dam is well suited for blocking river in wide valleys or narrow gorge ways. Since gravity dam must rely on its own weight to hold back water, it is necessary that it be built on a solid foundation of bedrock.

This is an example of a large dam used for hydroelectric power generation

Important features or parts of a dam

1. Crest- crest is the top of the dam that is used as a walkway across the dam.
2. Parapet walls- low protective walls on either side of the walkway on the crest.
3. Heel- this is a portion of dam that is in contact with the ground or a river-bed near the upstream side.
4. Toe: a portion of dam in contact with ground or river-bed at downstream side.
5. Spillway- it is an arrangement made (a kind of passage) near the top of a dam for the passage of excess water flowing out from the reservoir.
6. Abutments- this are the valley slopes located on either side of the dam wall to which the left &
7. Sluice way- it is an opening in the dam near the base; it is constructed to clear the silt accumulation in the reservoir.
8. Free board- this is the space between the highest level of water in the reservoir and the top of the dam, in which the right ends of dam are connected.
9. Gallery- a level or gently sloping tunnel- like passage (a small room like space) at transverse or longitudinal within the dam with drain on floor for seepage water. This may also be used to keep all the instruments used for studying the performance of dam.
10. Dead Storage level- this is the level of permanent storage below which prevents the withdrawal of water.
11. Diversion Tunnel- it is a tunnel constructed to divert or change the direction of water to bypass the dam construction site.

Importance of dam

1. A dam is constructed to provide access to safe and sufficient water supply to rural areas.
2. A dam provides rural energy to meet the cultural, social and economic developmental need of the communities.
3. Dams may also be seen as man-made habitats for fish and other wildlife
4. Dams are popular sites for boating and fishing and they are used for many other recreational activities.
5. They may be used to store water for hydroelectric power generation, irrigation and could be used to control floods within and area.
6. For provision of water for domestic purposes, such as washing, cleaning, cooking and drinking.