Disadvantages of Dams: Impact on Environment and People

Disadvantages of Dams Overview

Dams are one of the most magnificent and well-known features of modern infrastructure. Dams have played an important part in the expansion and evolution of civilization throughout history. Several ancient city designers depended on dams to channel water through their towns despite their remote location, but military leaders exploited dams to modify the area in which they intended to battle. With the growth in population and their insatiable wants, humanity began to build dams to hold extra water from rainfall once it entered the river stream. Dams are used to generate hydroelectricity in addition to storing water for direct use. Dams may also serve as tourist attractions; for example,the Nagarjuna Sagar dam in Andhra Pradesh is a popular tourist destination.

What are Dams?

A dam is a structure placed on a river, stream, or estuary to save water. It directly contributes to the provision of enough water for human consumption, industrial use, and agriculture. Modern dams are broadly grouped into two types-

Concrete Dams

Concrete or brick dams prevent streams from flowing through narrow gorges.

Embankments

Embankments regulate streams and rivers flowing over large valleys.

Example of Dams

The Nagarjuna Sagar Dam in Andhra Pradesh is an example of a masonry dam in India. The Tehri Dam in Uttarakhand is an example of an embankment dam in India. A huge portion of India's population is affected by a water crisis or poor water resource management. To begin with, many sections of the nation do not have adequate clean water for consumption or agriculture. Flash floods, on the other hand, are common in many areas. To address this recurrent issue, man-made structures such as dams and reservoirs have been built across streams and rivers.

List of 5 Largest Dams in India

The following are the 5 largest dams in India-

1. Tehri Dam, Uttarakhand
2. Hirakud Dam, Odisha
3. Sardar Sarovar Dam, Gujarat
4. Bhakra Nangal Dam, Himachal Pradesh
5. Nagarjuna Sagar Dam, Andhra Pradesh.

Disadvantages of Dams

Dams, despite their numerous advantages, have a substantial number of drawbacks. The following are some of the disadvantages of dams-

1. People are displaced during construction.
2. Reservoirs frequently produce a large proportion of greenhouse gases.
3. Often destroys local ecosystems.
4. It causes a disruption in the groundwater table.
5. Water cannot flow to other nations, states, or regions.

Read more about the Terrestrial Ecosystem and Importance of Ecosystem.

Disadvantages of Dams: Impact on the Environment 

Dams interrupt the normal water flow of rivers, disrupting the ecological balance of the related flora and animals. Environmentalists, human rights advocates, and concerned indigenous people have repeatedly protested dam development. The Narmada Bachao Andolan is a well-known social campaign spearheaded by locals opposing multiple dam development projects along the Narmada River, which is considered the lifeline of the Indian states of Gujarat and Madhya Pradesh. Dams, particularly large ones, can generate a slew of issues in the surrounding region, particularly in the zone behind the dam as the water rushes towards the obstruction. Some of the major disadvantages of dams that impact the environment are as follows-

Destruction of the Surrounding Habitat

Downstream reservoirs envelop the surrounding areas, flooding the habitats of the living forms that co-existed on the river's banks. This type of invasion damages plants and displaces wildlife and humans, lowering the overall quality of fauna and flora.

Habitat Fragmentation

Dams provide an artificial barrier to flowing rivers and the aquatic life that lives in them. particularly migratory fishes that nest and reproduce upstream and downstream along the river. This has a direct impact on the species' population and, as a result, reduces the number of preceding and succeeding life forms in the food chain. Dams must be specially designed to allow fish and other species to get over them.

Negative Impact on Aquatic Animals

There are several detrimental consequences for aquatic life. Because dams obstruct the flow of moving bodies of water, such as rivers, any creatures that rely on the flow to breed or as part of their life cycle are endangered. Migratory fish that mate in a completely different place from where they live the remainder of their lives, for example, are unable to reproduce and may go extinct. Water accumulation is also hazardous to flowers that grow on the water's natural limit. Plant life may become submerged and perish.

Sediment Deposition behind the Dam

It occurs as rivers and streams deposit sediments, enhancing the fertility of the soil along the banks. Yet, when the dam is built, the sediment load is deposited behind the dam, forming new deltas, banks, braided channels, and so on. Plant life and distribution are affected by variations in sedimentation.

Sediment Erosion Downstream

Sediments that would have settled downstream accumulate behind the dam. As a result, it reduces the sediment load downstream and promotes downstream erosion. Because of the absence of silt, the riverbed deepens and shrinks with time. During the first decade of damming, this riverbed deepens by several meters. Changes in sediment buildup have a detrimental influence on a variety of physical processes and downstream life forms' habitats. Also, seasonal farmlands that developed before as a result of downstream sedimentation are becoming increasingly rare.

Serving as a source of Methyl-Mercury Production

The stagnant water in the reservoirs is remineralized and can serve as a source of methylmercury. The reservoirs generate an environment in which decaying organic matter may convert mercury into methyl-mercury. Methylmercury is an exceedingly poisonous chemical that accumulates in plants, aquatic creatures, and people.

Water Gas Composition Changes

The submerged region near dams kills trees and plants, and their decomposition depletes the oxygen content in the water. Because the decomposition of plants and trees releases a significant quantity of carbon into the atmosphere. When stagnant river water depletes natural oxygen levels, a situation emerges in which methane, a greenhouse gas, is created at the bottom of reservoirs and eventually released into the atmosphere, contributing to global warming.

Disadvantages of Dams: Impact on People

Along with lowering the quality of life in and around the dam, it has also had an impact on the people who live around the reservoirs. The following are some of the effects of dams on people-

Relocation

Residents in the depression zone are frequently displaced when water from reservoirs encroaches on their houses and properties. And they lose their farms and companies, causing an economic downturn. In certain circumstances, indigenous people are forcibly evicted in order to acquire land for dam building.

Man-Made Flood

When reservoirs reach dangerously high levels, dam managers unleash floodgates, potentially causing an untimely flood downstream. These man-made floods have an impact on city transportation and economic loss.

Ecological Harm

As witnessed in the case of the Hoover Dam in the United States. The dam's construction caused regular earthquakes and lowered the earth's surface. This is very concerning, as it would otherwise result in widespread damage.

Dam Longevity

Old dams are known to burst and bring massive floods down the river, killing many people. Despite the fact that new technology and safety standards are addressed in freshly built dams.

Dam Building and Upkeep

It continues to be an expensive and time-consuming operation. In India, a dam project might cost anywhere from Rs 372 crore to Rs 7,777 crore, imposing a financial strain on the country.

Dams created Disputes among Countries

Dams that are erected over rivers that run between two countries have generated national disputes. The dammed river may cause water scarcity in neighboring countries, prompting them to respond. As shown in the cases of India and Pakistan, or West Bengal, India's easternmost state, and Bangladesh.

Points to Remember

1. Dams provide hydroelectricity while also preventing waterlogging in flood-prone locations. Furthermore, the reservoir water is used for home and industrial uses, to channel water into dry spell areas, and for leisure activities like rafting, boating, and so on.
2. The production of methane at the bottom of reservoirs contributes to global climate change.
3. The reservoirs have been remineralized and may now be used as a supply of methylmercury. Methylmercury is a very poisonous chemical that accumulates in the body.
4. The temperature of the water in the reservoirs changes dramatically across depth and surface, making aquatic life difficult to sustain.
5. Dammed rivers overwhelm the creatures' habitats and nearby territories. Such invasions damage flora and force wildlife and humans to relocate.
6. The decomposing stuff in reservoirs' stagnant water creates significant amounts of carbon, decreasing the water's oxygen content.
7. Dams force people to evacuate, while man-made floods destroy towns and assets and place an economic burden on the country.