Distribution of the Earth's water
Topic: Oceans: Hydrological Cycle, Relief of the Ocean Floor, Temperature and Salinity · NCERT: Class 11, Ch 12 "Water (Oceans)"
Meaning
The distribution of the Earth's water describes where all the planet's water is kept. About 97% is salt water in the oceans. NCERT gives an older figure of 91%, and USGS gives 96.5%. Only about 2.5% is fresh water. Of this fresh water, about 69% is frozen in glaciers and ice caps and about 30% is groundwater (water stored under the ground). Only about 1% is in lakes, rivers, soil, the air and living things. This explains why a "water planet" can still run short of usable water.
Example
Most of the world's fresh water is frozen in the ice sheets of Antarctica and Greenland, so people cannot easily use it. In India, Himalayan glaciers store fresh water that feeds rivers like the Ganga. Even so, the share people can actually use from rivers and lakes is small.
Don't confuse with
- NCERT's 91% figure: this is an older value. In a statement question, "oceans hold 91% of Earth's water" is false by current data (about 97%).