The realm of water is called Hydrosphere. It comprises various sources of water and different types of water bodies like lakes, rivers, seas, oceans etc. Water is a cyclic removable resource. Hydrological cycle is the circulation of water in different forms i.e. the liquid, solid and the gaseous phases. It is the continuous exchange of between the oceans, atmosphere, land surface and all organisms. There are six stages in water cycle. They are:
1. Evaporation: Transformation of water from the earth surface to the atmosphere is called Evaporation.
2. Transportation: The movement of water from the ocean to land through atmosphere is called transportation.
3. Condensation: It means condensing the transported water vapour forming tiny droplets and clouds.
4. Precipitation: It occurs in the form of rain, sleet or snow when the clouds meet cool air over land.
5. Run off: Most of the water returns to the land as run off. Some of it penetrates into the ground water and the rest returns to the oceans as river flow.
6. Ground water: Under special circumstances ground water flows upward in artesian wells.