Hydrosphere

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 3. Hydrosphere


        

  • The entire body of water on the surface of the earth in various forms is termed the hydrosphere.  The hydrosphere is the combined mass of water found on, under, and above the surface of the earth. It has been estimated that there are 1386 million cubic kilometers of water on earth (Environemtal Geography 1996). This includes water in liquid and frozen forms in groundwater, oceans, lakes and streams. Approximately 75% of Earth’s surface, an area of some 361 million square kilometers, is covered by ocean.

   

Distribution of water on the Earth.


Water can be seen in different forms on earth as follows. 

  • Ocean water (in oceans and seas)
  • Surface water (on the surface of the land, rivers, streams, lakes and reservoirs)
  • Ground water (water deposited underground.)
  • Atmospheric water (Atmospheric humidity)
  • Soil water (water in soil)

Out of the total volume of global water only 1% or a very limited amount of fresh water found on the surface of land, can be utilized by man.





  • Water is essential for the sustenance of all the bio systems. Water is utilized for drinking and domestic purposes as well as for agricultural, industrial and transportation activities.


Hydrological Cycle


  • The continuous process by which water is circulated throughout the earth and the atmosphere through evaporation, condensation, precipitation, and the transpiration of plants is known as the water cycle.

  • The atmosphere gets the water that is evaporated from the surface of the land and water bodies and also the water transpired from plants. This water which exists as water vapor in the atmosphere is subjected to condensation and returns to the earth as rainfall through the process of precipitation.

  • A part of the water received on the surface of the earth flows as surface runoff and another part of it is infiltrated into the land. The infiltrated water is stored in the earth as ground water and the springs and wells are fed by this infiltrated water.





  • In fact, Solar Energy is the source of heat and light, and gravity causes the transfer from one state to another over periods from hours to thousands of years. Most evaporation comes from the oceans and is returned to the earth as snow or rain.




Impact of human activities on the hydrosphere


  • The activities of modern society are having a severe impact on the hydro local cycle. The dynamic steady state is being disturbed by the discharge of toxic chemicals radioactive substances and other industrial wastes and by the seepage of mineral fertilizer, herbicides, and pesticides into surface and subsurface aquatic systems. Inadvertent and deliberate discharge of petroleum, improper sewage disposal, and thermal pollution also are seriously affecting the quality of the hydrosphere.

  • The present discussion focuses on three major problems-eutrophication, acid rain, and the buildup of the so-called greenhouse gases. Each exemplifies human interference in the hydrologic cycle and its far-reaching effects.









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