• Archeological and historical records show that from ancient times we have been constructing sophisticated hydraulic structures like dams built of stone rubble, reservoirs or lakes , embankments and canals for irrigation .
  • We have continued this tradition in modern India by building dams in most of our river basins .

What are Dams?

  • A dam is a barrier across flowing water that obstructs , directs or retards the flow , often creating a reservoir , lake or impoundment.
  • “Dam” refers to the reservoir rather than the structure.
  • Most dams have a section called a spillway or weir over which or through which it is intended that water will flow either intermittently or continuously .
  • Dams are classified according to structure , intended purpose or height
  • Based on structure and the materials used , dams are classified as timber dams , embankment dams or masonry dams , with several subtypes.
  • According to the height , dams can be categorised as large dams and major dams or alternatively as low dams , medium height dams and high dams .

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How do dams help in conserving and managing water?

  • Dams were traditionally built to impound rivers and rainwater that could be used later to irrigate agricultural fields .
  • Today, dams are built not just for irrigation but for electricity generation , water supply for domestic and industrial uses , flood control , recreation , inland navigation and fish breeding .
  • Dams are now referred to as multi-purpose projects where the many uses of the impounded water are integrated with one another.
  • For example, in the Sutluj-Beas river basin , the Bhakra-Nangal project water is being used both for hydel power production and irrigation .
  • The Hirakud Project in the Mahanadi basin integrates conservation of water with flood control .
  • Multipurpose projects , launched after Independence with their integrated water resources management approach, were thought of as the vehicle that would lead the nation to development and progress , overcoming the handicap of its colonial past . Jawaharlal Nehru proudly proclaimed the dams as the ‘ temples of modern India’ .
  • The reason being that it would integrate development of agriculture and the village economy with rapid industrialisation and growth of the urban economy .

Negative Impacts of Dams

  • In recent years, multi-purpose projects and large dams have come under great scrutiny and opposition for a variety of reasons.
  • Regulating and damming of rivers affect their natural flow causing poor sediment flow and excessive sedimentation at the bottom of the reservoir , resulting in rockier stream beds and poor habitats for the river's aquatic life
  • Dams also fragment rivers making it difficult for aquatic fauna to migrate , especially for spawning .
  • The reservoirs that are created on the flood plains also submerge the existing vegetation and soil leading to its decomposition over a period of time.
  • Multi-purpose projects and large dams have also been the cause of many new environmental movements like the ‘Narmada Bachao Andolan’ and the ‘Tehri Dam Andolan’ etc.
  • Resistance to these projects has primarily been due to the large-scale displacement of local communities .
  • Local people often had to give up their land, livelihood and their meagre access and control over resources for the greater good of the nation .
  • Perhaps, the landowners and large farmers , industrialists and few urban centres are only benefitting from such projects .    

Narmada Bachao Andolan

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  • Narmada Bachao Andolan or Save Narmada Movement is a Non Governmental Organisation (NGO) that mobilised tribal people , farmers , environmentalists and human rights activists against the Sardar Sarovar Dam being built across the Narmada river in Gujarat .
  • It originally focused on the environmental issues related to trees that would be submerged under the aim to enable poor citizens , especially the oustees (displaced people ) to get full rehabilitation facilities from the government .
  • People felt that their suffering would not be in vain.
  • Accepted the trauma of displacement believing in the promise of irrigated fields and plentiful harvests .
  • So, often the survivors of Rihand told us that they accepted their suffering as sacrifice for the sake of their nation .
  • But now, after thirty bitter years of being more precarious, they keep asking: “Are we the only chosen to make sacrifices for the nation?”.


Negative Impacts of Irrigation - Teachoo.png

  • Irrigation has also changed the cropping pattern of many regions with farmers shifting to water intensive and commercial crops .
  • This has great ecological consequences like salinisation of the soil .
  • At the same time, it has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor .
  • In Gujarat , the Sabarmati-basin farmers were agitated and almost caused a riot over the higher priority given to water supply in urban areas , particularly during droughts .
  • Inter-state water disputes are also becoming common with regard to sharing the costs and benefits of the multi-purpose project .

Disadvantages of Multi-purpose projects

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  • Most of the objections to the projects arose due to their failure to achieve the purposes for which they were built .
  • Ironically, the dams that were constructed to control floods have triggered floods due to sedimentation in the reservoir .
  • Moreover, the big dams have mostly been unsuccessful in controlling floods at the time of excessive rainfall
  • The release of water from dams during heavy rains aggravated the flood situation in Maharashtra and Gujarat in 2006 .
  • The floods have not only devastated life and property but also caused extensive soil erosion .
  • Sedimentation also meant that the flood plains were deprived of silt , a natural fertiliser , further adding on to the problem of land degradation .
  • It was also observed that the multi-purpose projects induced earthquakes , caused water-borne diseases and pests and pollution resulting from excessive use of water .
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Davneet Singh's photo - Co-founder, Teachoo

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.