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Nam Khan flows into the Mekong at Luang Prabang in Laos Mouth of Nam Khan.JPG
Nam Khan flows into the Mekong at Luang Prabang in Laos

A tributary, [1] or affluent, [2] is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. [3] A tributary does not flow directly into a sea or ocean. [4] Tributaries and the main stem river drain the surrounding drainage basin of its surface water and groundwater, 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 4,248 km (2,640 mi). The Madeira River is the largest tributary river by volume in the world with an average discharge of 31,200 m3/s (1.1 million cu ft/s).


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. [5] Distributaries are most often found in river deltas.


At Harpers Ferry, West Virginia looking downstream, the Shenandoah River (bottom right) meets the Potomac River, which flows from bottom left to top right, making the Shenandoah a right tributary of the Potomac, not a left tributary. Harpers Ferry WV aerial.jpg
At Harpers Ferry, West Virginia looking downstream, the Shenandoah River (bottom right) meets the Potomac River, which flows from bottom left to top right, making the Shenandoah a right tributary of the Potomac, not a left tributary.

"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). [6]

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'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. [6]

Another method is to list tributaries from mouth to source, in the form of a tree structure, stored as a tree data structure.[ citation needed ]

See also

Related Research Articles

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The Madeira River is a major waterway in South America. It is estimated to be 1,450 km (900 mi) in length, while the Madeira-Mamoré is estimated near 3,250 km (2,020 mi) or 3,380 km (2,100 mi) in length depending on the measuring party and their methods. The Madeira is the biggest tributary of the Amazon, accounting for about 15% of the water in the basin. A map from Emanuel Bowen in 1747, held by the David Rumsey Map Collection, refers to the Madeira by the pre-colonial, indigenous name Cuyari.

The River of Cuyari, called by the Portuguese Madeira or the Wood River, is formed by two great rivers, which join near its mouth. It was by this River, that the Nation of Topinambes passed into the River Amazon.

<span class="mw-page-title-main">IJssel</span> River in the Netherlands

The IJssel is a Dutch distributary of the river Rhine that flows northward and ultimately discharges into the IJsselmeer, a North Sea natural harbour. It more immediately flows into the east-south channel around the Flevopolder, Flevoland which is kept at 3 metres below sea level. This body of water is then pumped up into the IJsselmeer.

<span class="mw-page-title-main">Distributary</span> Stream branching off from main stream channel

A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel, a phenomenon known as river bifurcation. A distributary is effectively the opposite of a tributary, a stream that flows towards and into another, larger stream or river. Distributaries are often found where a stream approaches a lake or an ocean; as such, they are a common feature of river deltas. They can also occur inland, on alluvial fans, or where a tributary stream bifurcates as it nears its confluence with a larger stream. In some cases, a minor distributary can divert so much water from the main channel that it can later become the main route.

<span class="mw-page-title-main">Xiang River</span> River in China

The Xiang River is the chief river of the Lake Dongting drainage system of the middle Yangtze, the largest river in Hunan Province, China. It is the 2nd largest tributary in terms of surface runoff, the 5th largest tributary by drainage area of the Yangtze tributaries. The river flows generally northeast through the provinces of Guangxi and Hunan, its tributaries reaching into Jiangxi and Guangdong.

<span class="mw-page-title-main">Feather River</span> River in California, United States

The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about 73 miles (117 km) long. Its length to its most distant headwater tributary is just over 210 miles (340 km). The main stem Feather River begins in Lake Oroville, where its four long tributary forks join—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley. The total drainage basin is about 6,200 square miles (16,000 km2), with approximately 3,604 square miles (9,330 km2) above Lake Oroville.

<span class="mw-page-title-main">Huai River</span> River in Central China

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 east. Historically draining directly into the Yellow Sea, floods have changed the course of the river such that it now primarily discharges into the Yangtze. The Huai is notoriously vulnerable to flooding.

<span class="mw-page-title-main">Liao River</span> Major river in Northeast China

The Liao River is the principal river in southern Northeast China, and one of the seven main river systems in China. Its name derived from the Liao region, a historical name for southern Manchuria, from which the Liaoning province, Liaodong Peninsula and Liao dynasty also all have derived their names. The river is also popularly known as the "mother river" in Northeast China. Coursing 1,345 kilometres (836 mi) long, the Liao River system drains a catchment basin of over 232,000 square kilometres (90,000 sq mi), but its mean discharge is quite small at only about 500 cubic metres per second (18,000 cu ft/s), about one-twentieth that of the Pearl River. The Liao River has an exceedingly high sediment load because many parts of it flow through powdery loess.

<span class="mw-page-title-main">River island</span> Exposed landmass within a river.

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<span class="mw-page-title-main">Confluence</span> Meeting of two or more bodies of flowing water

In geography, a confluence occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river ; or where two streams meet to become the source of a river of a new name ; or where two separated channels of a river rejoin at the downstream end.

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The Kaweah River is a river draining the southern Sierra Nevada in Tulare County, California in the United States. Fed primarily by high elevation snowmelt along the Great Western Divide, the Kaweah begins as four forks in Sequoia National Park, where the watershed is noted for its alpine scenery and its dense concentrations of giant sequoias, the largest trees on Earth. It then flows in a southwest direction to Lake Kaweah – the only major reservoir on the river – and into the San Joaquin Valley, where it diverges into multiple channels across an alluvial plain around Visalia. With its Middle Fork headwaters starting at almost 13,000 feet (4,000 m) above sea level, the river has a vertical drop of nearly two and a half miles (4.0 km) on its short run to the San Joaquin Valley, making it one of the steepest river drainages in the United States. Although the main stem of the Kaweah is only 33.6 miles (54.1 km) long, its total length including headwaters and lower branches is nearly 100 miles (160 km).

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The Crooked River is a tributary, 125 miles (201 km) long, of the Deschutes River in the U.S. state of Oregon. The river begins at the confluence of the South Fork Crooked River and Beaver Creek. Of the two tributaries, the South Fork Crooked River is the larger and is sometimes considered part of the Crooked River proper. A variant name of the South Fork Crooked River is simply "Crooked River". The Deschutes River flows north into the Columbia River.

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Beaver Creek is a tributary of the Crooked River in the U.S. state of Oregon. It is formed by the confluence of its two forks in southeastern Crook County, a sparsely populated part of Central Oregon. North Fork Beaver Creek flows south and then west around Laughlin Table. South Fork Beaver Creek drains the slopes of Snow Mountain and Funny Butte in southwestern Grant County before joining the North Fork.


  1. "tributary"., Michael Pidwirny & Scott Jones, 2009. Viewed 17 September 2012.
  2. "affluent". The American Heritage Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. Viewed 30 September 2008.
  3. "Definition of TRIBUTARY". Merriam-Webster .
  4. Krebs, Robert E. (2003). The Basics of Earth Science. Greenwood Publishing Group. ISBN   978-0-313-31930-3.
  5. "opposite to a tributary"., Michael Pidwirny & Scott Jones, 2009. Viewed 17 September 2012.
  6. 1 2 Bisson, Peter and Wondzell, Steven. "Olympic Experimental State Forest Synthesis of Riparian Research and Monitoring", United States Forest Service, p. 15 (1 December 2009).