question_answer 6)

Answer the following questions in about 30 words.   (i) Explain how water becomes a renewable resource.   (ii) What is water scarcity and what are its main causes?   (iii) Compare the advantages and disadvantages of multi-purpose river projects.  

Answer:

(i) Water becomes a renewable resource through the hydrological cycle. Fresh water is mainly obtained from the surface run off and groundwater is continually being renewed and recharged through the hydrological cycle.   (ii) Water Scarcity Shortage of water as compared to its demand is known as water scarcity. The main causes of water scarcity are as follows—   (a) Growing Population A large population means more water requirement for cooking, washing and bathing.   (b) Industrialization The ever increasing number of industries pressure on the existing fresh water resources. Industries are heavy users of water.   (c) Commercialization of Agriculture Commercial crops need more water and other inputs. Assured means of irrigation like tube wells and canals are responsible for the falling of ground water levels. (iii) The various advantages and disadvantages of multi-purpose river projects can be compared as given in the table below—    

S.N.	Advantages	Disadvantages
1.	Irrigation of crops	Natural flow of river is affected causing poor flow of sediments also.
2.	Electricity generation	Excessive sedimentation of the reservoir.
3.	Water supply tor industrial and  domestic purposes	Stream   beds become rockier, affecting marine life.
4.	Flood control	Dam fragments a river thus making it difficult for aquatic fauna to migrate and spawn.
5.	Inland navigation	Reservoirs submerge the existing vegetation and soil leading to its decomposition over time.
6.	Fish breeding	Deforestation and displacement of local people.