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Compare the advantages and disadvantages of multi-purpose river projects.


Multipurpose river projects help in irrigation, electricity production, flood control, inland navigation and fish breeding.

At the same time the multi-purpose river projects also destroy local flora and fauna. Many native villages get submerged, and people lose their livelihood, with little or no hope of rehabilitation.

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Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out. 


Rain water harvesting was commonly practised to store drinking water, particularly in Rajasthan.

(i) In the 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.

(ii) The tanks could be as large as a big room; one household in Phalodi had a tank that was 6.1 metres deep, 4.27 metres long and 2.44 metres wide. The tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard. 

(iii) 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’. The first spell of rain was usually not collected as this would clean the roofs and the pipes. The rainwater from the subsequent showers was then collected.

(iv) The rainwater can be stored in the tankas till the next rainfall making it an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers.

(v) 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.

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Describe how modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.


Fortunately, in many parts of rural and urban India, modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.


(i) In Gendathur, a remote backward village in Mysore, Karnataka, villagers have installed, in their household’s rooftop, rainwater harvesting system to meet their water needs. Nearly 200 households have installed this system and the village has earned the rare distinction of being rich in rainwater. Gendathur receives an annual precipitation of 1,000 mm, and with 80 per cent of collection efficiency and of about 10 fillings, every house can collect and use about 50,000 litres of water annually. From the 20 houses, the net amount of rainwater harvested annually amounts to 1,00,000 litres.


(ii) Tamil Nadu has made roof top rainwater harvesting structure compulsory to all the houses across the state. There are legal provisions to punish the defaulters.


(iii) In Meghalaya, a 200-year-old system of tapping stream and spring water by using bamboo pipes, is prevalent. About 18-20 litres of water enters the bamboo pipe system, gets transported over hundreds of metres, and finally reduces to 20-80 drops per minute ate the site of the plant.

Roof top rain water harvesting is the most common practice in Shillong, Meghalaya. It is interesting because Cherapunjee and Mawsynram situated at a distance of 55 km. from Shillong receive the highest rainfall in the world, yet the state capital Shillong faces acute shortage of water. Nearly every household in the city has a roof top rain water harvesting structure. Nearly 15-25 per cent of the total water requirement of the household comes from roof top water harvesting.

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