NCERT Class 10 Geography Chapter 3: Water Resources Completes Notes Part 3

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Water Resources

Dams Classification

  • Based on height – large, medium, small

  • Based on material - timber, embankment or masonry

Image of Dams Classification

Image of Dams Classification

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Now here you have the diagram that shows the Dams and you have the upstream areas and the Downstream areas, as you can see there is significant change of the gradient and because of this change in the gradient when water moves down. You have hydroelectric energy that is generated and this is the head or the initial part of the Dam and this is the toe, you have the spill away that is located within the Dam and through which water comes to the downstream level.

Now there are various types of Dams which we can classify. Based on the height we can say there are large dams, medium dams and small dams. Based on the material there can be timber dams, embankment dams or masonry dams.

Limitations of Damming

  • Poor sediment flow

  • Excessive sedimentation at the bottom of the reservoir - rockier stream beds and poorer habitats for the rivers’ aquatic life.

  • Fragment rivers – migration of aquatic fauna & spawning gets difficult

  • Reservoirs on floodplains - submerge existing vegetation and soil leading to its decomposition

  • Farmers move to water intensive crop – salinization

  • Rising gap b/w rich and poor

  • Gives rise to inter-state disputes (allowing Cauvery water/Indus water)

  • Displacement of local people

  • Narmada Bachao Andolan & Tehri Dam Andolan

Now let’s understand what are the basic limitation of a damming areas? Now since you are creating a dam on the naturally flowing river what would happen you would have immense water that would be stored in the upstream areas and this water would be used in the nearby agricultural lands. Since you would be ample of water you would be growing water intensive crops like rice which could be grown in the region close to the multi learning projects.

Now since you are growing water intensive crops what would happens, these regions would have problems of salinization that would gain. Then again most of the dams are between the borders of two states. So there are inter-state disputes that starts up you have excessive sedimentation that takes places at the bottom of the reservior again you are fragmenting the river stream into two, so you have upstream and downstream so the migration of the aquatic fauna and aquatic flora, becomes difficult so you are artificially creating a boundary that is preventing the migration of animals or plants to and fro, again building a reservior on the floodplains would lead to submergence of the with the existing vegetation and it would lead to decomposition of the soil so these are some of the primary concerns that the region has. besides this since you are building such a huge infrastructure it would lead to seismic imbalance so there would be a induction of earthquakes so there could be chances of seismic disturbances in that area.

Again for building such a structure you would have to displace the local people or the local tribes and communities. So those are again some of the prior concerns. So the Narmada Bachao Andolan & Tehri Dam Andolan are some of the major examples where you have kind of revolved from the local people who are living there.