[Biology Class Notes] on Disadvantages of Dams Pdf

Dams are one of the foremost spectacular and well-noticed aspects of contemporary infrastructure. Throughout history, dams have played a vital role in the growth and enlargement of civilization. Many ancient town planners relied on dams to funnel water through their cities even though it was far-off, whereas military leaders used dams to change the parcel that they planned to fight on. However, their existence is contentious.

As the population grows, so do human needs. With the increase in population and their infinite needs, humans started constructing dams to store the excess water from rainfall after the water joins the river stream. Apart from storing water to consume it directly as a resource, dams are also used to generate hydroelectricity. Dams also act as a tourist spot, for example, Nagarjuna Sagar dam in Andhra Pradesh is one of the major tourist destinations. They provide a livelihood to the fishing communities living near the dams. They are the major source on which we can fall back in case of flood or drought. 

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Impact on Environment and People

The environmental consequences of huge dams vary from time to time and from place to place and include direct impacts to the biological, chemical and physical properties of rivers and bank (or “stream-side”) environments.

Dams, particularly the giant ones, may cause a lot of problems for the surrounding areas, especially the zone behind the dam where the water flows toward the blockage.

1. Negative Impact on Aquatic Animals: There are many negative effects on aquatic life. Since dams block up flowing bodies of water, such as rivers, any animals that depend on the flow to reproduce or as part of their life cycle are put in danger. Migratory fish that mate in a very completely different location than they live the rest of their lives, for instance, are unable to mate and may decline in population. The build-up of water is additionally dangerous for flowers that grow on the natural boundary of the water. The plant life may get submerged and die.

2. Impact on the Waterbody: The beneficial sediment that normally is washed down the river is blocked, which decreases the fertility of the soil downriver from the dam. The alteration of a river’s flow and sediment transport downstream of a dam often causes the greatest sustained environmental impacts. When a watercourse is devoid of water then its sediment load increases, it tends to recollect it by eroding the downstream river bed and banks (which can undermine bridges and alternative bank structures, as well as riverside woodlands). Riverbeds downstream of dams are typically eroded by several meters within the decade of first closing a dam; the damage can extend for tens or even hundreds of kilometers below a dam.

The dam additionally captures sediments, which are extremely important for maintaining physical processes and other habitats downstream of the dam. These also include the formation and maintenance of productive deltas, fertile floodplains, coastal wetlands, and barrier islands.

3. Impact on the Overall Aquatic Ecosystem: Another significant and obvious impact is the transformation upstream of the dam from a free-flowing river ecosystem to an artificial slack-water reservoir habitat. Changes in temperature, chemical composition, dissolved element levels and therefore the physical properties of a reservoir are typically not appropriate to the aquatic plants and animals that evolved with a given river system. Indeed, reservoirs typically host non-native and invasive species (e.g. snails, algae, predatory fish) that further undermine the river’s natural communities of plants and animals. Large dams have junction rectifiers to the extinction of the many fish and alternative aquatic species, huge losses of forest, the disappearance of birds in floodplains, erosion of deltas, wetland, and farmland, and many other irreversible impacts. Fish ladders have been built at some dams to help fish migrate, but some are not able to use the ladder properly, especially if they are used to fast-moving water.

4. Impact on the Groundwater Table: Riverbed deepening will also lower groundwater tables along a river, lowering the water table accessible to plant roots (and to human communities drawing water from wells). The building of the Dyke in Egypt has altered the amount of formation. This is slowly resulting in harm to the many of its ancient monuments as salts and damaging minerals are deposited within the stonework from rising damp caused by the changing water table level.

5. Impact on Biosphere: In aggregate, dammed rivers have also impacted processes in the broader biosphere. Most reservoirs, particularly those within the tropical zones, contribute tons to gas emissions (a recent study pegged world gas emissions from reservoirs on par with the aviation trade, about 4% of human-caused GHG emissions). Recent studies on the Congo have shown that the sediment and nutrients carried by the Congo drive biological processes badly into the Atlantic, that include serving as a carbon sink for atmospheric greenhouse gases.

6. Erosion of Encompassing Soil: With the development of the many dams, erosion of the surrounding land has been noticed. The large reservoir at China’s 3 Gorges Dam has worn near the boundary, which has led to landslides along the side of the reservoir. The Nile Delta has older erosion thanks to the reduction of sediment with the development of the urban centers. Much of the sediment has fallen into the reservoir, which implies there’s less land around to farm and work on.

7. High Price & Risk for Disaster: The price of building a dam usually reaches a level that may become difficult to recover. The engineering and technical aspects, alongside the particular construction, could be time intensive. Moreover, the heavy method used in the construction should be through with absolute exactness and precision. China’s Three Gorges Dam was built in an area with seismic activity, and small cracks have already been found in the infrastructure. A dam collapse or break would be an absolute catastrophe, especially from one the size of the Three Gorges Dam. After Hurricane Harvey hit Texas, dams in the Houston area were pushed to their limit by massive floodwaters.

According to the American state Observer, worries are that water may overflow from a number of the dam’s spillways, and not be controlled. If a dam is removed, rivers and alternative waterways would possibly attempt to reclaim its recent chann
el, which means that expensive river training structures, like bank protection, needs to be implemented in order to keep the river on the desired course. This is usually difficult to try and do and depends on the accuracy of hydraulic modeling studies and alternatively advanced analytics.

 

Some Other Disadvantages Include

• Relocation is another big concern. People living in villages and cities that are within the natural depression zone that might be flooded, should move out. Hence, they lose their farms and businesses. In some countries, people are forcibly removed so that hydro-power plant constructions can go ahead. This happens to be an ethical concern.

• The building of large dams can result in serious ecological damage. For example, the building of the Hoover Dam in the USA prompted a number of earthquakes and has depressed the earth’s surface at its location. This is an alarming matter as it may lead to devastation.

• Although modern planning and design of dams have been less prone to the devastating results, in the past old dams have been known to be ruptured. This has led to deaths and flooding in several places.

• Dams built on or near the border between two countries may also block the progress of a river in one country. This means that the water supply from the same river in the neighboring country is not under their control anymore. This can result in serious issues between neighboring countries. For example, the neighboring countries like India and Pakistan on one hand and West Bengal, an eastern state of India and Bangladesh are at constant conflict due to the water supply from the Indus river and Teesta River respectively.

• Building dams need huge amounts of money and resources, this might strain the government’s budget if the economy of the country is really small. The government needs to take care of the strict implementation of the rules and regulations while constructing such huge structures. 

• When people are relocated from their original places where the dam is being constructed, they not only lose their home but also have to find a new livelihood in a new place. 

• Ethical issues arise out of these constructions when the people are forcibly shifted to another place without following strict guidelines.

• Such huge dams might trigger natural disasters like earthquakes which will have bad repercussions 

• As the dams are built with huge resources, they have to run for many years to generate enough income to cover up the costs incurred for construction.

Life in and around a stream or any waterbody evolves and is conditioned on the temporal order and quantities of stream flow. Disrupted and altered water flows can be as severe as the completely de-watering river reaches and the life they contain may be a danger. Yet even refined changes within the amount and temporal order of water flow impact aquatic and bank life, which can unravel the ecological web of a river system.

 

Conclusion

It may be difficult to imagine what civilization would be like if there was no presence of dams to regulate waterways and build reservoirs of water. Even though dams are a significant part of the trendy infrastructure, their positives and negatives on society and also the surroundings are still being studied.