Construction of dams have been done since the time of human civilization. The first dam was built by the King Seti in 1319 BC. Those ancient dams are operational till today and offer the much-required water for hydropower and irrigation. Building of dams need loads of natural resources and materials. It also has a widespread influence on fauna and flora of an aquatic world. Let us see how dams impact the environment in positive and negative ways.
Positive impact of dam on the environment:
Construction of dams in rivers impact processes in the wider biosphere. Most of the reservoirs significantly contribute towards emissions of greenhouse gases. According to the recent studies, the flow of nutrient and sediment drives biological process that serves as a “carbon sink” for greenhouse gases.
Dams provides a good source of water for the purpose of irrigation. This is the prime reason for the construction of dams. Majority of countries are scarce on water resources and rely on monsoon water for irrigation purpose.
However, due to sudden changes in seasonal weather conditions, dam building is seen to be an essentiality to offer much-needed water to the local population. Dams help them to combat any kind of water scarcity that is not fulfilled by a poor monsoon.
Provision of drinking water:
There is one more reason why countries encourage construction of dams. It is because dams act as a major source for drinking water. It provides population with essential drinking water throughout the year. In some cities, due to poor rains, natural calamities like earthquakes and depleted water resources, river gets dried up very soon.
This makes it necessary to build dams to combat shortage of water. Most of the dams provide fresh drinking water and electricity to people in the local area.
Use of dam for the generation of hydro-electricity is another modern invention by scientists. Now dams can be built for generation of hydroelectric power. The water gets passed under high pressure through turbines. It causes them to rotate at high speeds that produces electricity. One dam can provide a lot of electricity that is sufficient to power up one small town, for one complete year. Also, this energy is devoid of any greenhouse gases and toxic fumes. This makes it a lot more beneficial for a nation.
Negative effects of dam on environment:
Construction of dams negatively impacts the environment in various ways. The adverse environmental outcome caused by a large dam is varied, and numerous. It directly influences the chemical, physical and biological properties of environment and rivers. Let us see more about them.
Restricts migration of fishes
The walls of the dam hinder migration of fishes, that separates rearing habitats and spawning habitats. It also traps sediment that are vital for maintaining physical procedures and habitats. Some of these procedures include the upkeep of useful deltas, fertile floodplains, barrier islands, and wetlands.
Altered flow of water
The deviation of the flow of river and transport of sediment causes immense continued impacts on the environment. Life inside a river is conditioned on the amounts and timing of flow of river. Changed or disturbed water flow can cause a lot of harm to the marine life. Subtle changes in the timing and quantity of water flow influences marine life, that can loosen the environment of a river.
Results in inappropriate survival conditions
Dam transforms the free-flowing ecosystem to an unnatural slack-water pool habitat. It brings modifications in temperature, dissolved oxygen levels, the physical attributes of a reservoir and its chemical composition that are not appropriate for the survival of marine animals. Dams host invasive and non-native species such as snails, predatory fish and algae that destabilize the natural groups of marine habitats.
Erodes river beds
Dam will replenish downstream ecosystems naturally. It deprives a river from the load of sediment, and seek to capture it again by corroding the river bed and banks. Deepening of riverbed lowers groundwater table that makes it inaccessible to the roots of aquatic plants. Such alteration in the riverbed lowers habitat that breeds in the bottom of river.
To save the environment from its negative impact, it becomes essential to evaluate and maintain dams, on a regular basis. This will help a lot in avoiding a few of its negative impacts, like large-scale flooding that is the outcome of complete dam failure.
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