Dams – Environmental Effects

Oct 31, 2012   //   by admin   //   Knowledge Base  //  No Comments

Dams – Environmental Effects


Since prehistoric times Dams and Reservoirs are a medium of generating power, supply drinking water and irrigational purposes. Dams have very useful for the social and economic development of the area. Local people depend on dams for many purposes like irrigation, electricity generation, drinking water supply, fishery, tourism etc. They have very important role in development of under developed areas.  No doubt dams are very useful to human society but, environmental and social impacts of these can’t be ignored.

Although they have so many benefits but there is also a loss to environment in certain aspects irrespective of the place. Therefore it becomes important to consider all the positive and negative aspects of constructing a dam. Given below  are the negative impacts of dams on environment:-

•           The main purpose of constructing a dam to moderate floods in the area. But this agenda is hardly achieved. The natural habitat gets flooded and disturbs the environment and agriculture badly. The newly constructed dams have large surface area hence an increase in evaporation. Hence, adds to climate change.

•           The initial filling floods may submerge many of plants and trees. The carbon rich plants and trees later on decompose and releases CO2 and other greenhouse gases in the atmosphere.

•           Since dams need a large mass of land all archaeological and historical places with exceptional beauties disappear underlying in water.

•           Further the decaying plant material settles down in the anoxic bottom of the reservoir ultimately releases methane gases leading to biomass degradation by anaerobic processes.

•           In some cases, where flooded basins are wide and biomass volumes are high the amount of biomass converted to methane results in pollution potential 3.5 times more than an oil-fired power plant would for the same generation capacity.

•           The construction of dams blocks the sedimentation downwards that leads to an increased sedimentation in the reservoir and reduced water capacity. With reduced water storage capacity there’s decrease in the ability to produce electricity, less water availability for irrigation, and expiration of dam if ignored.

•           Since the rate of sediment deposition is highly concentrated and the rate of flow is constant the water erodes the river shores threatening ecosystems, excavating the river bed and contracting river channels.

•           Slow water movement of rivers responds to an increase of no of diseases in the area especially in tropical areas. As it is a home for several trajectories of diseases such as mosquitos, snails etc.

•           When water is released to maintain the flow will cause an adverse effect on fisheries. They act as an obstacle between the upstream and downstream movement of migratory river animals and give rises to illegal transportation of migratory fishes.

•          These have negative impact on the reproduction of the aquatic animals as egg beds are destroyed or deteriorated.

•           There will be serious changes in the water quality as a result of drainage water returning from irrigation.

•           These have effect on rotation of earth seismically because the change in movement of water.

•           As a result of increased surface area there will be more evaporation hence resulting into climate change.

•           The flow of river becomes stationary in its downstream since the water level in the stream bed does not change significantly. Therefore, energy flow characteristics modify in the living ecosystem.

•           As a result of downstream & slow movement of water the surface layer of water is likely to absorb heat from the sun resulting into warmer temperature while the bottom part remains cold. This results into ‘Starification’ which further have adverse effects on aquatic life as there as oxygen-depleted depths.

•           There’ll be changes in temperature of river water as well as chemical qualifications depending upon the reservoir depth hence changing the biological ecosystem.

•           Dams and the construction of reservoirs also require relocation of potentially large human population if are near to residential areas. The construction of dam needs a large land mass that may lead to thousands of peoples of evacuate from that place that leads mental trauma, economic catastrophe. They hardly get a compensation for leaving their native places.

•           Territorial ecosystems are severely effected during the dam construction as a result of changes in water-land boundary.

After summing up all benefits and negative aspects of Dam construction it becomes important to take initiatives towards minimising these negative effects for a sustainable development. May be the benefits in future subside these negative effects still Precaution is much better then cure. Any change in ecosystem will result in to ultimate destruction.

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