A tributary, or affluent, is a stream or

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

that flows into a larger stream or

main stem In hydrology, a mainstem (or trunk) is "the primary downstream segment of a river, as contrasted to its tributaries". Water enters the mainstem from the river's drainage basin, the land area through which the mainstem and its tributaries flow.. A ...

(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 large ...

. A tributary does not flow directly into a

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

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 unconsolidated ...

, leading the water out into an ocean. The

Irtysh The Irtysh ( otk, 𐰼𐱅𐰾:𐰇𐰏𐰕𐰏, Ertis ügüzüg, mn, Эрчис мөрөн, ''Erchis mörön'', "erchleh", "twirl"; russian: Иртыш; kk, Ертіс, Ertis, ; Chinese: 额尔齐斯河, pinyin: ''É'ěrqísī hé'', Xiao'e ...

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 delta A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more ra ...

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 A current in a fluid is the magnitude and direction of flow within that fluid, such as a liquid or a gas. Types of fluid currents include: * Air current * Boundary current * Current (stream), a current in a river or stream * Longshore 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 in ...

, 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 , name_etymology = , image = American River CA.jpg , image_size = 300 , image_caption = The American River at Folsom , map = Americanrivermap.png , map_size = 300 , map_caption ...

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 A tree structure, tree diagram, or tree model is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, although the chart is genera ...

, 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 The Adamawa Plateau (french: Massif de l'Adamaoua) is a plateau region in west-central Africa stretching from south-eastern Nigeria through north-central Cameroon ( Adamawa and North Provinces) to the Central African Republic. The part of the pl ...

; 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 The Huai River (), formerly romanized as the Hwai, is a major river in China. It is located about midway between the Yellow River and Yangtze, the two longest rivers and largest drainage basins in China, and like them runs from west to ea ...

(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 flows ...

) and tributaries File:Jialingrivermap.png,

Jialing River The Jialing River, formerly known by numerous other names, is a major tributary of the Yangtze River in the Sichuan Basin. It is named after the Jialing Valley in Feng County, Shaanxi through which it flows. The Jialing River's most notable c ...

(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 The Taizi River () is a major river in the Liaoning province of Northeastern China. The river was historically also known as Yan River (衍水) or Liang River (梁水). It was originally the third largest tributary of the Liao River, southern ...

, Dongliao River, Xinkai River,

Xiliao River The Xiliao or West Liao River () is a river in Inner Mongolia and Liaoning province, in northeast China. Its source is the Xilamulun River in Inner Mongolia. It is one of the headwaters of the Liao River. The Xiliao or "Western Liao River", hi ...

Xar Moron River The Xar Moron river ( mn, Shar mörön Шар мөрөн, "Yellow River";the X is used roughly like in Hanyu Pinyin here, i.e. to present an "sh"-like sound. The cyrillic spelling, as used in Outer Mongolia, would be Шар Мөрөн. Outer Mong ...

and the Laoha River. The Xiliao River's tributaries are the Xar Moron and Laoha rivers. File:Mekongbasin.jpg, The

Mekong The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...

is a trans-boundary river, originating in the

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the ...

. 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 The Mun River ( th, แม่น้ำมูล, , ), sometimes spelled ''Moon River'', is a tributary of the Mekong River. It carries approximately of water per year. Geography The river begins in the Khao Yai National Park area of the Sankam ...

) cover larger areas. File:Vermilion wabashrivermap.png, The water basin of the

Wabash River The Wabash River (French: Ouabache) is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed May 13, 2011 river that drains most of the state of Indiana in the United States. It flows from ...

; 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 fl ...

. File:Yamunarivermap.jpg, The

Yamuna The Yamuna ( Hindustani: ), also spelt Jumna, is the second-largest tributary river of the Ganges by discharge and the longest tributary in India. Originating from the Yamunotri Glacier at a height of about on the southwestern slopes of B ...

is the second-largest tributary river of the

Ganges The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...

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 so ...

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

Triveni Sangam In Hindu tradition, Triveni Sangam is the confluence (Sanskrit: ''sangama'') of three rivers that is also a sacred place, with a bath here said to flush away all of one's sins and free one from the cycle of rebirth. Triveni Sangam in Allaha ...

, Allahabad.

References

{{Authority control Physical geography River morphology Rivers Water streams

Terminology

Ordering and enumeration

Gallery

See also

References