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

"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]

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 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.

Other Languages
Alemannisch: Nebenfluss
العربية: رافد (نهر)
aragonés: Afluent
বাংলা: উপনদী
Bân-lâm-gú: Pun-lâu
беларуская: Прыток
български: Приток
bosanski: Pritoka
català: Afluent
čeština: Přítok
dansk: Biflod
Deutsch: Nebenfluss
eesti: Lisajõgi
Ελληνικά: Παραπόταμος
español: Afluente
Esperanto: Alfluanto
estremeñu: Afluenti
euskara: Ibaiadar
فارسی: ریزابه
français: Affluent
Gaeilge: Craobhabhainn
Gàidhlig: Leas-abhainn
galego: Afluente
한국어: 지류
Հայերեն: Վտակ
हिन्दी: उपनदी
hrvatski: Pritok
Bahasa Indonesia: Anak sungai
italiano: Affluente
עברית: יובל (נהר)
ქართული: შენაკადი
қазақша: Сала
Kiswahili: Tawimto
kurdî: Mil (çem)
latviešu: Pieteka
lietuvių: Intakas
lumbaart: Aflüent
македонски: Притока
मराठी: उपनदी
მარგალური: ნადუ
Nederlands: Zijrivier
norsk: Sideelv
norsk nynorsk: Sideelv
occitan: Afluent
Oromoo: Tributary
oʻzbekcha/ўзбекча: Irmoq
polski: Dopływ
português: Afluente
română: Afluent
русский: Приток
Simple English: Tributary
slovenščina: Pritok
српски / srpski: Притока
srpskohrvatski / српскохрватски: Pritoka
suomi: Sivujoki
svenska: Biflod
தமிழ்: துணை ஆறு
тоҷикӣ: Шохоб
Türkçe: Kol (akarsu)
українська: Притока
Tiếng Việt: Phụ lưu
Võro: Harojõgi
ייִדיש: בייטייך
žemaitėška: Ėntaks
中文: 支流