From the beginning rivers have played an important in the life of man.Man of the earliest times used the rivers as a means of travel.Today rivers still serve as a great waterway for the transport and people. In ancient times, man settled near rivers or on river banks and built up large empires. Water is nature's most valuable gift to man.Man needs water to irrigate his crops, to cook and to wash.In nations all over the world, rivers mean life and wealth.They feed and clothe the nations around them. Water is also a source of energy and power.Man build huge dams across the rivers to control the water for irrigation and get the energy needed to drive generators.The electrical power is then directed to homes, cities, factories and television stations. Man uses water each day.In a small way rivers help to keep man in good health and provide for his amusements.Various forms of water sports keep man strong and healthy. Man in old times traveled from one continent to another   _  .
by air by sea by train by bus