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Geography NCERT

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Lesson 6, Topic 3
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Chapter- 3 Water Resources

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Multi-Purpose River Projects and Integrated Water Resources Management

  • Dams are built to impound rivers and rainwater that could be used later to irrigate agricultural fields.

  • 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.

  • Hence, dams are now referred to as multi-purpose projects. For example, in the Sutluj-Beas river basin, the Bhakra –Nangal project water is being used both for hydel power production and irrigation. Similarly, the Hirakud project in the Mahanadi basin integrates conservation of water with flood control.

  • A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment.

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 poorer habitats for the rivers’ aquatic life.

  • Dams also fragment rivers making it difficult for aquatic fauna to migrate, especially for spawning. The reservoirs that are created on the floodplains 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 social 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 getting benefited.

  • Irrigation 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.

  • 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.

  • Big dams have mostly been unsuccessful in controlling floods at the time of excessive rainfall.

  • 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.

  • 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.

Rainwater Harvesting

  • In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture.

  • ‘Rooftop rain water harvesting’ was commonly practised to store drinking water, particularly in Rajasthan.

  • In the flood plains of Bengal, people developed inundation channels to irrigate their fields.

  • In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stand and moisten the soil like the ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan.

  • Semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water.

  • The tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard. They were connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops would travel down the pipe and was stored in these underground ‘tankas’.

  • Rainwater, or palar pani, as commonly referred to in these parts, is considered the purest form of natural water.

  • Many houses constructed underground rooms adjoining the ‘tanka’ to beat the summer heat as it would keep the room cool.