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Disadvantages of Dams, Practice Problems and FAQs

A situation without water is unimaginable. We realise the value of water only when it is unavailable. But there are people around us who suffer in drought. If a place is not getting enough rain, the whole vegetation of the region is affected. It will also affect the agricultural practices and eventually it will affect the food production of that country. So are there any solutions to this problem? Dams are one of the solutions to prevent desertification of land. Through building a dam, the flow of the water of a river is blocked and the water is stored in a reservoir. This water can be used for irrigation purposes and other human needs when there is a scarcity of water.

Have you ever visited a dam? If yes, you might have an idea about the size of a dam and the amount of water it can hold. Each dam has its own unique water holding capacity. Kariba Dam in Zimbabwe has the largest water storage capacity.

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Fig: Kariba Dam

The dam should be strong enough to hold the water, since it is built across the flowing river or stream and has to experience a huge amount of pressure. A flowing water can apply a great amount of force on anything which tries to stop their flow. So while constructing a dam, we have to consider many things like the strength of the walls, capacity of the reservoir etc. Dams usually open in the rainy season, when the water in the river rises above the capacity of the dam.

Fig: The measuring scale showing the capacity of a dam

Dams are built for human needs. But don't you think that, just like every other human invention, dams also have some disadvantages. What are the disadvantages of a dam? Let's discuss more about it in this article.

Table of contents:

  • Dams
  • Disadvantages of dams
  • Practice Problems
  • FAQs

Dams

A structure built on rivers and streams as a barrier that can stop or restrict the flow of water are called Dams. The major function of a dam is to store water and provide it to the population.

Reservoirs created by the dams can suppress the flood. The collected water in the dam is distributed between different locations. The fields where the water of dams are utilised are as follows:

  • Agriculture
  • Domestic use
  • Industrial use
  • Aquaculture
  • Navigation
  • Generation of electricity (hydroelectric power)

Fig: Water from dam using for agricultural purposes

Dams also works as a tourist spot which encourages a site for fishing, boating and other recreational activities. When water scarcity or drought happens, then dams are a lifeline.

Fig: Dams as picnic spots

Disadvantages of Dams

A country invests a lot into the construction and maintenance of dams due to the numerous advantages associated with them. But there are some negative impacts of dams which can impact the biological, chemical and physical properties of the rivers and the environment surrounding them. The consequences can vary depending on the time and place.

The major disadvantages of dams can be explained under the following headings:

  • Impact on cost
  • Impact on relocation
  • Impact on aquatic animals
  • Impact on erosion
  • Impact on water bodies
  • Impact on groundwater
  • Impact on ecosystem
  • Risk of disaster
  •  

Impact on cost

The building cost of a dam is very high. The designing and construction of a dam is done by expert engineers and they need more time and a good pay scale. The construction works are labour intensive and it also adds more expenses to the total cost of the project. Strict guidelines have to be followed by the Government and a high standard has to be maintained while constructing dams. It would take many years or decades to compensate for the invested money, even if the dam is used for the generation of power and other recreational purposes.

Fig: Construction of dam

Impact on relocation

Constructing a dam on a river or stream causes instabilities to the life of people staying nearby. To prevent the population from catastrophic events like landslides, flood or earthquakes during the construction, the relocation of population should be done. This affects the business, lands and properties of a huge mass of people.

Fig: Relocation of people

Impact on aquatic animals

Through the construction of the dams, the reproduction of the aquatic animals which depend on the flow of water are affected. The dams also cause a block for the migratory fishes. This will negatively affect the whole aquatic life.

Fig: Aquatic life of river

Impact on erosion

Construction of dams and reservoirs for water conservation uses up a large mass of the surrounding land. Landslides are common in the shorelines near the water reservoirs. This causes loss of surrounding land mass and serious soil erosion, which affects the vegetation and consequently other living organisms.

Fig: Soil erosion

Impact on water bodies

The sediments carried by the water bodies are important for aquatic life and are important in the perpetuation of the carbon cycle. The erection of dams can block the path of these sediments causing the water bodies to create alternative paths or log over a single place. This will cause geological imbalance.

Impact on groundwater

The river bed deepens gradually because of the water reservoir of a dam which in turn reduces the groundwater. This will negatively affect the nearby trees and plants in the surrounding land mass as they won't have access to the ground water. Due to the stationary waterlog, the salts and minerals will form a rocky layer in the river bed. Both marine and terrestrial life forms get destroyed by this.

Fig: Aquatic and terrestrial life

Impact on ecosystem

The dams can affect the temperature, chemical composition, and physical conditions of their surroundings which may result in biological changes which can make the habitat unsuitable for the native organisms to live. As a result, extinction of many species occurs. Since this impact is irreversible over time, it is very important.

Risk of disaster

By the construction of a dam, many disasters like earthquakes, landslides, extinction, and erosion happen over time. Major catastrophes like earthquakes can occur as a result of the large reservoirs of dams. Dams can also cause territorial and political issues between two countries or states if they share the flow of a particular river.

Fig: Collapsing of a dam

Practice Problems

1. Which of the following is not a true statement regarding the dams?

  1. Dams are the structures that are built on rivers and streams as a barrier that can stop or restrict the flow of water.
  2. The major function of a dam is to store water and provide it to the population.
  3. Dams do not work as a tourist spot.
  4. The water of dams are utilised for the generation of electricity (hydroelectric power).

Solution: A structure built on rivers and streams as a barrier that can stop or restrict the flow of water are called Dams. The major function of a dam is to store water and provide it to the population. Reservoirs created by the dams can suppress the flood. The collected water in the dam is distributed between different locations. The fields where the water of dams are utilised are agriculture, domestic use, industrial use, aquaculture, navigation and generation of electricity (hydroelectric power). Dams also works as a tourist spot which encourages a site for fishing, boating and other recreational activities. When water scarcity or drought happens, then dams are a lifeline. Hence the correct option is c.

2. Which of the following is a disadvantage of dams?

A) Heavy cost

B) Relocation of population

C) Impact on aquatic animals

D) Soil erosion

E) Geological imbalance in water bodies

  1. A, B C and E
  2. A, B and E
  3. A, C, D, E
  4. All the above

Solution: A country invests a lot into the construction and maintenance of Dams, because there are numerous advantages like we discussed above. But there are some disadvantages for the dams which can impact the biological, chemical and physical properties of the rivers and the environment surrounding them. The consequences can vary depending on the time and place. The major disadvantages of dams are high cost, impact on relocation of nearby populations, negative impact on reproduction and migration of aquatic animals, soil erosion, geological imbalance in water bodies due to stagnation of sediments, reduction in groundwater, habitat destruction and biodiversity loss in an ecosystem and risks of disaster. Hence the correct option is d.

3. Suppose a dam construction is going on in your place and the authorities are informing you and your family to relocate from your place. What are the negative impacts which will affect your family?

Answer: Constructing a dam on a river or stream causes instabilities to the life of people staying nearby. To prevent the population from catastrophic events like landslides, flood or earthquakes during the construction, the relocation of population should be done. This affects the business, lands and properties of a huge mass of people.

4. Assertion: The construction of dams will affect the life of organisms.

Reason: A dam can affect the temperature, chemical composition, and physical conditions of its surroundings.

Which of the following options are correct for the given assertion and reason?

  1. Both assertion and reason are true and the reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is the correct explanation of assertion.
  3. Assertion is true, but the reason is false.
  4. Both assertion and reason are false.

Solution: The river bed deepens gradually because of the water reservoir of a dam which in turn reduces the groundwater. This will negatively affect the nearby trees and plants in the surrounding land mass as they won't have access to the ground water. Due to the stationary waterlog, the salts and minerals will form a rocky layer in the river bed. Both marine and terrestrial life forms get destroyed by this. The sediments carried by the water bodies are important for aquatic life and are important in the perpetuation of the carbon cycle. The erection of dams can block the path of these sediments causing the water bodies to create alternative paths or log over a single place which can cause geological imbalance. The dams can affect the temperature, chemical composition, and physical conditions of their surroundings which can cause biological changes that make the habitat unsuitable for the native organisms to live. As a result, extinction of many species occurs. Since this impact is irreversible over time, it is very important. Hence the correct option is a.

FAQs

1. How do dams cause earthquakes?

Answer: Earthquake is triggered by large reservoirs and this phenomenon is called Reservoir-induced Seismicity. This mainly depends on the water pressure created in the micro cracks and fissures in the foundation units of the dam. The earthquake occurs because of the tectonic strain released prematurely by the reservoirs.

Fig: Earthquake

2. What are floodgates?

Answer: The adjustable gates used to control the flow of water in the reservoir are called flood gates or stop gates. They are also used in flood barriers, rivers, streams etc. They can adjust the flow of water or can stop it.

3. Which is the largest dam in the world?

Answer: The largest dam in the world is the Three Gorges Dam situated in China. It is a hydroelectric gravity dam that spans the river called Yangtze.

4. What is a dam safety act?

Answer: The act aiming the surveillance ensurance, inspection, operation and maintenance of the specified dam is called a dam safety act. This act prevents the dam-failure related disasters and also provides an institutional mechanism to ensure the safe functioning of the dam.

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