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Important questions based on NCERT syllabus for Chapter 16 - Water: A Precious Resource:
Question-1: You must have seen many advertisements about conservation of water. We know that ¾ th of earth’s surface is filled with water. That is a huge amount of water. Then why should we conserve water?
Solution: It’s true that about ¾ th of earth’s surface is filled with water but not all of it can be used by us. The water in seas and oceans is saline water and cannot be used for day to day work. The fraction of usable water is very little and most of it is in the form of snow caps, glaciers. Only 0.006% water is available for use of all available in the form of rivers, lakes, ponds and ground water. Nowadays,
even these sources are being contaminated due to industrial and agricultural activities. Also, due to increasing population and uneven rainfall there is shortage of usable water. So, we need to conserve water.
Question-2: Akshit was very thirsty and went to draw water from his water purifier. But he found that the water tank was empty and needed to be refilled. Now, Akshit is wondering how come the water in rivers, lakes, seas and oceans never get over. Can you tell him why the water in these sources never gets over?
Solution: Water keeps flowing through nature according to the water cycle. Rivers, lakes, ponds and other sources get water through precipitation and melting of glaciers. The water from precipitation and these sources recharges the ground water through infiltration. The groundwater reaches the seas through ground water runoff and the water on surface reaches the seas through rivers. From the sea the water gets evaporated, reaches the atmosphere and forms clouds. Some ground water also
reaches the atmosphere through evaporation and transpiration. The clouds are responsible for precipitation and thus the water again reaches the rivers, lakes and ponds. So, the water keeps flowing and hence water never gets over in these sources.
Question-3: Find odd one out – Rainwater Harvesting, Agricultural activity, Drip irrigation
Solution: Agricultural activity. Rainwater Harvesting and Drip irrigation are methods to conserve water whereas Agricultural activity use a lot of water and pose a threat to water as a resource.