Kavana Sarma Kaburlu

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I am against aseries of dams all along the length of the river

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Sea water tries to intrude on to the land, below ground level always, and into the river at times when bottom of the river at the sea river junction is lower than the water level in the sea This is called intrusion of the Saline Wedge .The river water flowing above the ground and fresh water flowing under the ground level , try to arrest this intrusion. The ability to arrest depends on flow velocity and density difference . In the case of an unobstructed river, the soil which got saline due to salt wedge intrusion in lean flow season , gets flushed . Large dams attenuate floods greatly reducing velocities of fresh water and permit salinity intrusion deep into the land side. Anicuts cause damage to a less degree Series of dams along the length to store "every drop of water going wastefully into the sea " cause greatest salinity intrusion. There is another aspect., that is, drying up of seas due to damming of rivers or diverting rivers flowing into them.
River Darya in USSR was flowing into Aral sea . For irrigation purpose the river was completely diverted to agricultural fields.Now the sea has dried up more than 75% . The exposed land due to the sea drying , is several hundred sq.km in area and it is covered with white salt flakes . The salt flakes now rise hundreds of meters high under windy condition, travel hundreds of km and cover the land which was never under the sea causing salt pollution
84 % of evapouration of the water takes place from seas and 16 % from land area. 77 % of precipitation occurs on the seas and 23 % on the land . The excess 7% of precipitation flows as surface water( Rivers , streams etc.,) to the sea. When this water is stopped from flowing, the surface area of seas decrease until eventually the evapouration matches the precipitation. The exchange between the surface waters and ground water is assumed to be in equilibrium .Melting of polar ice caps is also not taken into consideration . The damage is likely to be more serious if all aspects are considered but in a different way .
So the idea floated by Sir Arthur Cotton that water should not be allowed to flow wastefully to the sea, which is reasonable in the case of an anicut very close to
the sea , becomes untenable in the case of series of dams all along the length of the river.
Most of the damages occur not during the life time of the experts advocating and govt.s implementing them but a generation later.!

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Written by kavanasarma

June 25, 2016 at 2:05 pm

Posted in Uncategorized

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