Rivers Anduin & Entwash

River Anduin and its famous tributary, river Entwash

A tributary or affluent is a stream or river which flows into a "main stem" (or parent) river. A tributary does not flow directly into a sea, ocean, or lake. Tributaries and their main stem river serve to drain the surrounding drainage basin of its surface water and groundwater by leading the water out into an ocean or some other large body

A confluence is where two or more bodies of water meet together, usually referring to the joining of tributaries

The Anduin had many tributaries (about eight or nine known), the river Entwash being the greatest of them. A mighty delta was formed where the two rivers met, measuring a hundred miles from the splitting of the Entwash to its final inflow into the Anduin. This delta formed the Mouths of Entwash.


'Right tributary' and 'left tributary' (or 'right-bank tributary' and 'left-bank tributary') are terms stating the position of the tributary relative to the flow of the mainstem river. These terms are defined from the perspective of looking downstream (in the direction the water current is going).

Reciprocal to a tributary is a "distributary", a river that branches off of and flows away from the main stream.

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