The hydrosphere refers to the water bodies that are found on the earth’s surface. More than 71% of the earth is covered with water. This water is found in all its forms—ice, water and water vapour. Running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere. More than 97% of the earth’s water is found in oceans. The ocean water is very salty, hence not of human utility. A large proportion of the rest of water is in the form of the icesheets and glaciers or under the ground. A very small percentage (0.03%) is available as fresh water. It is this water that we use.