When the Earth was created and when mountains and seas had just been formed, the falling rain-water formed zigzag paths while coming down-hill.
Over the years, the continuous flow of water made these tracks deeper and wider. These streams of water underwent many changes and subsequently became rivers.
Today most rivers start from mountains. They get their water from the melting snow and glaciers. For example, the river Ganga originates from a glacier in the Himalayas called Gangotri.
During the summer months, when the temperature rises, ice melts and the river Ganga flows down into the plains. It passes through many cities of northern and eastern India before falling into the Bay of Bengal.
Interestingly, a river does not move at the same speed all the time. Typically, a river flows very fast from its point of origin, but as it advances, it slows down.
A river is slowest near the end of its journey, before it finally drains into other water bodies.
A flowing river carries a lot of sediments with it. This soil gets collected at the point where a river meets the sea or a lake. The place where a river meets the sea or ocean is called a delta. The sediments deposited by rivers make deltas very fertile. The largest delta in India is the Sunderbans.
