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Looking upstream, the Shenandoah River (left) is a tributary of the larger Potomac River (right) Aerial Photo of Harpers Ferry (15646790473).jpg
Looking upstream, the Shenandoah River (left) is a tributary of the larger Potomac River (right)

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.


A confluence, where two or more bodies of water meet together, 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.


Looking downstream, the Shenandoah River (bottom right) meets the Potomac River which flows from bottom left to top right, so the Shenandoah is a right tributary of the Potomac, not a left tributary Harpers Ferry WV aerial.jpg
Looking downstream, the Shenandoah River (bottom right) meets the Potomac River which flows from bottom left to top right, so the Shenandoah is a right tributary of the Potomac, not a left tributary

"Right tributary" and "left tributary" (or "right-bank tributary" and "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 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.

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

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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.


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.

Distributary River branching off from main river

A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distributary is a tributary. Distributaries are found where a stream nears a lake or an ocean. 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 become the main route.

River delta Silt deposition landform at the mouth of a river

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position.

Xiang River

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 Guangxi and Hunan two provinces, its tributaries reach into Jiangxi and Guangdong.

Salmon River (Idaho)

The Salmon River is located in Idaho in the western United States, also known as "The River of No Return." It flows for 425 miles (685 km) through central Idaho, draining a rugged, thinly populated watershed of 14,000 square miles (36,000 km2). The river drops more than 7,000 feet (2,100 m) from its headwaters, near Galena Summit above the Sawtooth Valley in the Sawtooth National Recreation Area, to its confluence with the Snake River. Measured at White Bird, its average discharge is 11,060 cubic feet per second. It is one of the largest rivers in the continental United States without a single dam on its mainstem.

Feather River

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 together—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.

Body of water Any significant accumulation of water, generally on a planets surface

A body of water or waterbody is any significant accumulation of water, generally on a planet's surface. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ponds, wetlands, or more rarely, puddles. A body of water does not have to be still or contained; rivers, streams, canals, and other geographical features where water moves from one place to another are also considered bodies of water.

Huai 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 largest rivers 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 is now a major tributary of the Yangtze. The Huai is notoriously vulnerable to flooding.

Liao River

The Liao River is the principal river in southern Northeast China, and one of the seven main river systems in mainland 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.

Payette River

The Payette River is an 82.7-mile-long (133.1 km) river in southwestern Idaho and is a major tributary of the Snake River.

River island Exposed land within a river.

A river island is any exposed land surrounded by river water. Properly defined it excludes shoals between seasonally varying flows and may exclude semi-coastal islands such as in deltas.

Confluence Meeting of two or more bodies of flowing water

In geography, a confluence occurs where two or more flowing bodies of water join together 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.

Kaweah River

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).

River bifurcation

River bifurcation occurs when a river flowing in a single stream separates into two or more separate streams which continue downstream. Some rivers form complex networks of distributaries, especially in their deltas. If the streams eventually merge again or empty into the same body of water, then the bifurcation forms a river island.

Crooked River (Oregon)

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.

Drainage system (geomorphology)

In geomorphology, drainage systems, also known as river systems, are the patterns formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. Geomorphologists and hydrologists often view streams as part of drainage basins. This is the topographic region from which a stream receives runoff, throughflow, and its saturated equivalent, groundwater flow. The number, size, and shape of the drainage basins varies and the larger and more detailed the topographic map, the more information is available.

Stream Body of surface water flowing down a channel

A stream is a body of water with surface water flowing within the bed and banks of a channel. The flow of a stream is controlled by three inputs - surface water, subsurface water and groundwater. The surface and subsurface water are highly variable between periods of rainfall. Groundwater, on the other hand, has a relatively constant input and is controlled more by long-term patterns of precipitation. The stream encompasses surface, subsurface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls.

River Natural flowing watercourse

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 water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.

Hoquiam River

The Hoquiam River is a stream in the U.S. state of Washington. It has three main tributaries, the East Fork, West Fork, and Middle Fork Hoquiam Rivers. The main stem Hoquiam River is formed by the confluence of the West and East Forks. The Middle Fork is a tributary of the West 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 Sep. 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 (December 1, 2009).