Multipurpose Dams

Hydroelectricity is the electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy. In the early 21st century, hydroelectric power was the most widely utilized form of renewable energy; in 2019 it accounted for more than 18 percent of the world’s total power generation capacity.

Benefits of Hydropower Projects

  • Renewable
    • It is considered renewable because it uses earth’s natural water flow to generate electricity. Due to natural water cycle, water is recycled back to Earth and will never run out of supply.
    • The amount of hydroelectricity produced can vary because of drought and lower water levels, but this is seasonal.
  • Clean and safe
    • Unlike fossil fuels, biomass and nuclear power, hydroelectric power is a clean and green alternative source of energy. Since hydroelectric dams do not use fuel, they do not release any greenhouse gases or toxins into the environment.
  • Flexible
    • It is a flexible source of electricity as hydro plants can be scaled up and down quickly to meet the changing energy demands.
    • Compared to gas turbines or steam plants, the start-up time taken by hydro turbines is very less.
  • Cost-competitive energy source
    • Despite expensive upfront building costs, hydroelectric power is a cost-competitive source of energy.
    • Hydropower plants require low cost of maintenance and operation. Since they have few parts, the plants need minimal replacements.
    • Also, dams are typically designed for long-term use and are therefore capable of producing hydroelectric power up to an average lifetime of 50 – 100 years.
  • Additional benefits
    • Provide water for irrigation if the command area is developed.
    • Ground-water recharge in the area.
    • Assured source of drinking water.
    • The pond created is good source for fisheries and serves many ecological functions such as saving biodiversity. For ex. Pong Dam and Harike Dam have been recognized as Ramsar sites.
    • Tourist and water & adventure sports developments.
    • Flood moderation
pros and cons of hydropower

Concerns with hydropower projects

  • Failure risks
    • As dams hold back large volumes of water, a sub-standard construction, natural disasters or sabotage, and the extreme influx of water can be catastrophic to downriver settlements and infrastructure. For ex. There is concern over the safety of Mullaperiyar Dam between Kerala and Tamil Nadu. 
    • These failures not only affect the supply of power but also affect the flora, fauna and other forms of life.
    • Risk of reservoir induced seismicity. For ex. Koyna dam
  • Methane emissions
    • Hydroelectric dams contribute more to global warming than previously estimated by the anaerobic oxidation of plant material in inundated material which leads to substantial methane emissions.
  • May lead to local droughts
    • One of the main downsides of setting up hydroelectric power plants is the occurrence of local droughts.
    • The overall cost of energy is calculated depending on the availability of water and a drought could potentially affect this, causing people not to acquire the power they need.
  • Ecosystem damage and loss of wetlands
    • Big reservoirs cause submersion of extensive areas upstream of the dams, sometimes destroying lowland and riverine valley forests, marshland and grasslands rich in biodiversity.
    • They affect the natural hydrological cycle and threaten the surrounding aquatic ecosystems both upstream and downstream.
    • Since turbine gates are often opened intermittently, interruptions of natural water flow can have a great impact on the river ecosystem and the environment.
    • Fish in the river is affected by the draining of the water from the dam as well as the fish that is in the dam.
    • Animals such as birds, cranes and other aquatic birds, and some plant species thrive in marshy habitats. However, because of the hydroelectric power plant construction, these habitats will be destroyed.
  • Displacement of large population
    • People are forced to relocate to facilitate the construction of the dams needed to generate hydroelectricity often without comprehensive resettlement and rehabilitation. 
    • Local populations living downstream can become vulnerable to flooding due to the possible strong water currents that might be released from the dams.
    • The World Commission on Dams estimated in 2000 that dams had physically displaced 40-80 million people worldwide.
  • Other concerns
    • Substantial time and cost overruns.
    • Lack of completion of command area leads to suboptimal realization of irrigation potential.
    • Often in some areas, there is problem of water logging and soil salinity, leading to degradation of good agricultural lands.
    • Construction of large number of dams has reduced the amount of sediments reaching the delta regions particularly in Eastern India. This has led to increasing risk of submergence of these coastal areas.
    • Construction of dams involves use of lots of explosives and drilling which increases the risks of landslides particularly in Himalayan region.
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