About 71% of the earth's surface is covered with water. Water is present in oceans, seas, lakes, rivers, ice caps, as groundwater and in the atmosphere. Water exists in different forms. On the earth's surface, there are three different forms of water namely solid, liquid and gaseous.
The Earth's water cycle is the global mechanism by which water moves from the air to the Earth (precipitation) and eventually back to the atmosphere (evaporation).