Tamilnadu BoardEnglish MediumSTD 8Social ScienceGEOGRAPHY CH3 Hydrologic Cycle5 Marks
Question
Water on the Earth – Explain.
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Answer
About 71 % of the earth’s surface is covered by water.
The quantity of water present on the earth is about 326 million cubic miles.
It is hard to visualise this massive quantity of water.
Most of the water on the earth is saline and is found in seas and oceans.
The salt water constitutes about 97.2% and the fresh water is only about 2.8%.
Out of this 2.8%, about 2.2% is available as surface water and the remaining 0.6% is groundwater. From this 2.2% of surface water, 2.15% is available in the form of glaciers and icecaps, 0.01% in lakes and streams and the remaining 0.04% is in other forms.
Only about 0.25% of the total ground water of 0.6% can be economically extracted with the present drilling technology.
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