what is the material source of river?
Answers
The source of a river is its beginning. A river's source is the point on the river that is farthest from its mouth. Many rivers are generated when rain falls from the mountains, but they can also originate from a lake, a marsh, or a bog, or a spring where water rises from the earth.
"The distance from the mouth to the farthest distant headwater source (irrespective of stream name), or from the mouth to the headwaters of the stream popularly known as the source stream" is how a river's length is calculated. The USGS sometimes considers the Missouri River to be a tributary of the Mississippi River, as an example of the second definition above. However, it (like with practically all other geographic authorities and publications) uses the combined Missouri—lower Mississippi length figure in listings of river lengths all around the world, as does the first definition above. [1] The majority of rivers have several tributaries and frequently change names.