Water Resources

The water cycle ,through evaporation and precipition,maintains hydrological systems which form rivers and lakes and supports a variety of aquatic ecosystems.Wet lands are the intermediate forms between terrestrial and aquatic ecosystems are used by a large number of people for their daily needs usch as drinking water,washing cooking watering animals and irrigating fiels.However the world depends on limited quantity of fresh water water covers 70% of the Earth's surface,but only 3% of this is fresh water .Of this 2% is present as polar ice caps and 1% is usable water in rivers,lakes and subsoil aquires.Only a fraction of this can be actually used.At global level,70% of the water is used agriculture 7% for industry and 3% for domestic use.
One of the greatest challenges facing the world in this century is the need to rethink the overall management of water resources.The world population has passed the billion mark based on the proporattion of young people in developing countries this will continues to increase significantly during the new few decades.This places enormous demands on the world's limited fresh water supply.The total annual fresh water withdrawls today are estimated at 3800 cubic kilometers twice as much as just 50 years ago (world commision on Dams,2000),Studies indiacate that a oerson needs a minimum of 20 to 40 liters of water per day for drinking and sanitation .However,more than one billion people worldwode have no access to clean water,and to many more,water supplies are unreliable