A tributary, or affluent, is a stream or

river A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...

that flows into a larger stream or main stem (or parent) river or a

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...

. A tributary does not flow directly into a sea or

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

. Tributaries and the main stem river drain the surrounding

drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

of its surface water and

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidat ...

, leading the water out into an ocean. 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 The Madeira River ( pt, Rio Madeira, link=no ) is a major waterway in South America. It is estimated to be in length, while the Madeira-Mamoré is estimated near or in length depending on the measuring party and their methods. The Madeira is ...

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 river deltas.

Terminology

"Right tributary", or "right-bank tributary", and "left tributary", or "left-bank tributary", are terms stating the orientation of the tributary relative to the flow of the main stem river. These terms are defined from the perspective of looking downstream (in the direction the water current of the main stem is going).Bisson, Peter and Wondzell, Steven
"Olympic Experimental State Forest Synthesis of Riparian Research and Monitoring"

United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...

, p. 15 (1 December 2009). An early tributary is a tributary that joins the main stem river closer to the main river's source than its end. Similarly, a "late tributary" joins the main river much further downstream, closer to the main river's end point. In the U.S., 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 The Chicago River is a system of rivers and canals with a combined length of that runs through the city of Chicago, including its center (the Chicago Loop). Though not especially long, the river is notable because it is one of the reasons for ...

'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.

Ordering and enumeration

Tributaries are sometimes listed starting with those nearest to the source of the river and ending with those nearest to the mouth of the river. The Strahler stream order examines the arrangement of tributaries in a hierarchy of first, second, third and higher orders, with the first-order tributary being typically the least in size. For example, a second-order tributary would be the result of two or more first-order tributaries combining to form the second-order tributary. Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

data structure.

Gallery

File:Amazonriverbasin basemap.png, The basin of the Amazon River is a system made up of many tributary streams. The streams shown on the map besides the Amazon are tributaries of the Amazon. File:Benuerivermap.png, The Benue River is fed by multiple tributaries originating in the Adamawa Plateau; many of the highest tributaries are seasonal streams. The Benue is itself a major tributary of the

Niger ) , official_languages = , languages_type = National languagesHuai River (itself a tributary of the

Yangtze The Yangtze or Yangzi ( or ; ) is the longest river in Asia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains (Tibetan Plateau) and flow ...

) and tributaries File:Jialingrivermap.png, Jialing River (itself a tributary of the

) and tributaries File:Liaorivermap.png, The Liao River is a much simpler example of a river basin with tributaries. The main tributaries noted on this map are the Hun River, Taizi River, Dongliao River, Xinkai River, Xiliao River, Xar Moron River and the Laoha River. The Xiliao River's tributaries are the Xar Moron and Laoha rivers. File:Mekongbasin.jpg, The Mekong is a trans-boundary river, originating in the Tibetan Plateau. Its upper tributary river systems (e.g. ) are restricted to narrow gorges, but the tributaries that feed its lower reaches (e.g. the Mun River) cover larger areas. File:Vermilion wabashrivermap.png, The water basin of the Wabash River; the other rivers (not including the Ohio River) are tributaries of the Wabash River. The Vermillion River (and its forks) is a highlighted example of a tributary of the Wabash River. The Wabash River is also a tributary of the Ohio River, which in turn is a tributary of the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it ...

. File:Yamunarivermap.jpg, The Yamuna is the second-largest tributary river of the Ganges and the longest tributary in

India India, officially the Republic of India ( Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the ...

. It flows almost parallel to the Ganges about its right bank for before merging with it at the Triveni Sangam,

Allahabad Allahabad (), officially known as Prayagraj, also known as Ilahabad, is a metropolis in the Indian state of Uttar Pradesh.The other five cities were: Agra, Kanpur (Cawnpore), Lucknow, Meerut, and Varanasi (Benares). It is the admin ...

References

{{Authority control Physical geography River morphology Rivers Water streams

Terminology

Ordering and enumeration

Gallery

See also

References