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- 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 .
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
- 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?”.
Irrigation
- 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
- 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 .
