Question

What is the percentage of water held by the seas and oceans?
(A) 50%
(B) 75%
(C) 88%
(D) 97%

Answer 1

Hint: 71% of Earth’s surface is covered by water therefore, earth is known as ‘blue planet’. Water exists below the land surface and as water vapor in the air. It is a finite source. The Earth is a closed system, meaning that very little matter, including water, may leaves or enter the atmosphere; the water that was here billions of years ago is still here now. But, the Earth replenishes the water supply through the hydrologic cycle. Humans can use both underground water as well as surface water. Surface water constitutes approximately 80% of water used on a daily basis. It makes up the majority of the water used for public supply and irrigation. It plays less of a role in mining and livestock industries.

Complete answer:
The earth has an abundance of water but only a small portion (0.3%) is available for human use. The other 99.7 percent of water is present in Ocean, soil, ice caps and in the atmosphere in the form of water vapor. Water bodies which are visible are referred to as surface water. Majority of freshwater is actually found underground. Groundwater feeds the streams ,that’s why a river can flow even when there is no precipitation.
Distribution of the water on Earth: Distribution of water is extremely uneven.
Ocean water: 97.2 percent
Glaciers and other ice: 2.15 Percent
Groundwater, : 0.61 percent
Freshwater lakes: 0.009 percent
Inland seas: 0.008 percent
Soil Moisture: 0.005 percent
Atmosphere: 0.001 percent
Rivers: 0.0001 percent.

So, the correct option is (D). Ocean is the largest source of surface water, but because of high salinity, the water is not useful as drinking water. Efforts are being done to remove the salt from the water (desalination), but it is very costly. Salt water is used in industries, in the mining process, and in Power generation.

Note:
Though the salty water of the ocean is not of enough use but ocean plays a very important role in the hydrologic cycle ( water cycle). It provides habitats for thousands of marine species. Ocean regulates the global climate. People depend on water for drinking, washing, cooking, for waste removal, and for other domestic purposes. Water supply system must also meet requirements for public, industrial and commercial activities. In all cases, water must fulfill both qualitative and quantitative requirements.