Some rivers begin where a natural spring releases water from underground. The source of the River Thames is a spring. Some rivers begin in mountains or hills, where rain water or snowmelt collects and forms small channels, . At first, the channels are small and are called rills.Feb 12, 2018
Rivers carry water and nutrients to areas all around the earth. They play a very important part in the water cycle, acting as drainage channels for surface water. Rivers drain nearly 75% of the earth's land surface. Rivers provide excellent habitat and food for many of the earth's organisms.
A river usually ends by flowing into an ocean, a lake or a bigger river. The place where the river flows out into a bigger body of water is called the 'mouth' of the river.