The hydrosphere is one among the four spheres of the earth. It includes the water on the surface of the earth, the water below the surface called ground water and the water in the atmosphere. The atmosphere has water in all three forms (solid, liquid and gas). The total amount of water on the earth does not change over time; water is constantly transformed and reused, so the hydrosphere acts as a closed system. Over 90% of the world's fresh water is in Antarctica, and 85% of the world population lives in the driest half of the planet.
1. Distribution of Land and Water
| Item | Share |
|---|---|
| Water | 70.8% of the earth's area (361 million sq km) |
| Land | 29.2% (148 million sq km) |
| Salty water in seas and oceans | About 96.5% of water |
| Fresh water | Only 2.5% |
| Saline ground water and saline lakes | 1% |