Product Code Database
A tributary, "tributary". PhysicalGeography.net, Michael Pidwirny & Scott Jones, 2009. Viewed 17 September 2012. or an affluent, "affluent". The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Viewed 30 September 2008. is a stream or river that flows into a larger stream ( main stem or "parent"), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they flow, drain the surrounding drainage basin of its surface water and groundwater, leading the water out into an ocean, another river, or into an endorheic basin.
The Irtysh is a chief tributary of the Ob river and is also the longest tributary river in the world with a length of . The Madeira River is the largest tributary river by volume in the world with an average discharge of .
A confluence, where two or more bodies of water meet, 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. "opposite to a tributary". PhysicalGeography.net, Michael Pidwirny & Scott Jones, 2009. Viewed 17 September 2012. Distributaries are most often found in .
An early tributary is a tributary that joins the main stem river closer to its source than its mouth, that is, before the river's midpoint; a late tributary joins the main stem further downstream, closer to its mouth than to its source, that is, after the midpoint.
In the United States, where tributaries sometimes have the same name as the river into which they feed, they are called forks. These are typically designated by compass direction. For example, the American River in California receives flow from its North, Middle, and South forks. The Chicago River's North Branch has the East, West, and Middle Fork; the South Branch has its South Fork, and used to have a West Fork as well (now filled in).
Forks are sometimes designated as right or left. Here, the handedness is from the point of view of an observer facing upstream. For instance, Steer Creek has a left tributary which is called Right Fork Steer Creek.
These naming conventions are reflective of the circumstances of a particular river's identification and charting: people living along the banks of a river, with a name known to them, may then float down the river in exploration, and each tributary joining it as they pass by appears as a new river, to be given its own name, perhaps one already known to the people who live upon its banks. Conversely, explorers approaching a new land from the sea encounter its rivers at their mouths, where they name them on their charts, then, following a river upstream, encounter each tributary as a forking of the stream to the right and to the left, which then appear on their charts as such; or the streams are seen to diverge by the cardinal direction (north, south, east, or west) in which they proceed upstream, sometimes a third stream entering between two others is designated the middle fork; or the streams are distinguished by the relative height of one to the other, as one stream descending over a Waterfall into another becomes the upper fork, and the one it descends into, the lower; or by relative volume: the smaller stream designated the little fork, the larger either retaining its name unmodified, or receives the designation big.
Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a tree data structure.
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