A hydrosphere (Greek hydro means ‘water’) in physical geography described the collective mass of water found on, under, and over the surface of a planet. Hydrosphere covers more than two-thirds of the earth’s surface either as ocean (salt water) or as fresh water, which includes seas, rivers, lakes, ponds, etc. The oceans account for about 95 per cent of earth’s water supply. This is unfit for consumption due to its high salt content. The polar ice caps and glaciers account for about two per cent of the remaining water. Fresh potable water is available only to the extent of about one per cent in rivers, lakes and as groundwater.
In hydrosphere, water is present in all the three forms, viz., solid, liquid and gaseous. The major portion of hydrosphere are the oceans. Besides oceans, water is also present in inland seas, lakes, rivers, underground water, water vapor in the atmosphere and glaciers (in which water is present as snow) on an average, the depth of oceans is about 3, 794 m.
The hydrosphere is called the ‘Blue planet’; this is due to the looking at sea, which looks blue. In hydrosphere, approximately 70.8 per cent of earth is covered by water. Out of this water, about 97 per cent is the sea water. The availability of fresh water in the hydrosphere is only 3 per cent.
Water is the most essential component of life. It is unique liquid in the sense that without it no life is possible. Though on a global scale, there is abundance of water, but the main problem is the availability of water in the right place at the right time and in the right from.
The survival of mankind has always depended on water. It is well known that in earlier times, civilizations flourished on river beds. Also, the river beds were responsible for wiping out the populations due to floods. Water can be found in liquid, solid or gaseous form in a number of place Depending on the specific location, the residence time may vary from a few day to thousands of years (Figure Below).
Water has a high value of latent heat and it is this property that moderates the temperature of the biospheres. It is a universal solvent. The solubility of oxygen in water is responsible for survival of aquatic life. Though there is loss of water by evaporation, but its amount remains constant.
This is because there is a continuous circulation of water including water bodies and natural processes which use water. Due to rapid industrialization, human beings are responsible for the discharge of waste materials into water bodies like seas, oceans, rivers, etc. This has created serious problems for the survival of life not only on the land but also the survival of aquatic life.