River is a naturally flowing water body where Lake is any large area of water body surrounded by land from all sides. A confluence, where two or more bodies of water meet together, usually refers to the joining of tributaries. The opposite to a tributary is a distributary, a river or stream that branches off from and flows away from the main stream. Delta are located at the mouth of rivers which are formed due to the deposition of sediments. A river basin is the portion of land drained by a river and its tributaries. The overflow of river water over surface is termed as flood. Rivers also form valleys which are low land between two mountains or hill.

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