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A stream is a continuous body of
surface water Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by prec ...
flowing within the bed and
bank A bank is a financial institution that accepts deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital markets. Beca ...
s of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long large streams are usually called
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 wate ...
s, while smaller, less voluminous and more
intermittent Intermittency is a behavior of dynamical systems: regular alternation of phases of apparently periodic and chaotic dynamics. Intermittent or intermittency may also refer to: *Intermittent river or stream, the one that ceases to flow every year or ...
streams are known as streamlets, brooks or creeks. The flow of a stream is controlled by three inputs –
surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the s ...
(from
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, Rain and snow mixed, sleet, snow, ice pellets, ...
or
meltwater Meltwater is water released by the melting of snow or ice, including glaciers, glacial ice, tabular icebergs and ice shelf, ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reduc ...
), daylighted subterranean water, and surfaced
groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit ...
(
spring water A spring is a point of exit at which groundwater from an aquifer flows out on top of Earth's crust (pedosphere) and becomes surface water. It is a component of the hydrosphere. Springs have long been important for humans as a source of fresh w ...
). The surface and subterranean 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. Streams are important as conduits in the
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly const ...
, instruments in
groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical ...
, and corridors for fish and wildlife migration. The biological
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
in the immediate vicinity of a stream is called a
riparian zone A riparian zone or riparian area is the interface between land and a 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 gro ...
. Given the status of the ongoing
Holocene extinction The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event during the Holocene epoch. The extinctions span numerous families of bacteria, fungi, plants, and animals, including mammals, birds, reptiles, amphibians, fish, ...
, streams play an important corridor role in connecting
fragmented habitat Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred Environment (biophysical), environment (Habitat (ecology), habitat), causing population fragmentation and ecosystem decay. Causes of habi ...
s and thus in conserving
biodiversity Biodiversity or biological diversity is the variety and variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem d ...
. The study of streams and
waterway A waterway is any Navigability, navigable body of water. Broad distinctions are useful to avoid ambiguity, and disambiguation will be of varying importance depending on the nuance of the equivalent word in other languages. A first distinction ...
s in general is known as ''surface
hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
'' and is a core element of environmental geography.


Types


Brook

A stream smaller than a creek, especially one that is fed by a spring or
seep A seep or flush is a moist or wet place where water, usually groundwater, reaches the earth's surface from an underground aquifer. Description Seeps are usually not of sufficient volume to be flowing beyond their immediate above-ground location. ...
. It is usually small and easily forded. A brook is characterised by its shallowness.


Creek

A creek () or crick (): * In
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
,
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world ...
,
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...
and the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
, a (narrow) stream that is smaller than a river; a minor tributary of a river; a brook. Sometimes navigable by motor craft and may be intermittent. * In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
, and parts of
Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; ...
,
New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət ...
, a tidal
inlet An inlet is a (usually long and narrow) indentation of a shoreline, such as a small arm, bay, sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In ...
, typically in a
salt marsh A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open Seawater, saltwater or brackish water that is regularly flooded by the tides. It is ...
or
mangrove swamp Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because Mangrove, mangroves cannot wit ...
, or between enclosed and drained former salt marshes or swamps (e.g. Portsbridge Creek separating
Portsea Island Portsea Island is a flat and low-lying natural island in area, just off the southern coast of Hampshire in England. Portsea Island contains the majority of the city of Portsmouth. Portsea Island has the third-largest population of all th ...
from the mainland). In these cases, the "stream" is the tidal stream, the course of the
seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approx ...
through the creek channel at low and high tide.


River

A
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 wate ...
is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a
navigable A body of water, such as a river, canal or lake, is navigable if it is deep, wide and calm enough for a water vessel (e.g. boats) to pass safely. Such a navigable water is called a ''waterway'', and is preferably with few obstructions against dir ...
waterway A waterway is any Navigability, navigable body of water. Broad distinctions are useful to avoid ambiguity, and disambiguation will be of varying importance depending on the nuance of the equivalent word in other languages. A first distinction ...
.


Runnel

The linear channel between the parallel ridges or bars on a shoreline beach or river floodplain, or between a bar and the shore. Also called a swale.


Tributary

A
tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drainage b ...
is a contributory stream to a larger stream, or a stream which does not reach a static
body of water A body of water or waterbody (often spelled water body) is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as p ...
such as a
lake A lake is an area filled with water, localized in a Depression (geology), 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 World Ocean, oce ...
, bay or
ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distribution on Earth, Earth's water. An ocean can also refer to any of the ...
but joins another river (a parent river). Sometimes also called a branch or fork.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 United States Department of Agriculture, U.S. Department of Agriculture that administers the nation's 154 United States National Forest, national forests and 20 United States Nationa ...
, p. 15 (December 1, 2009).


Distributary

A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel, and the phenomenon is known as
river bifurcation River bifurcation (from la, furca, fork) occurs when a river flowing in a single stream separates into two or more separate streams (called distributary, distributaries) which then continue downstream. Some rivers form complex networks of distri ...
. Distributaries are common features of
river delta A river delta is a landform shaped like a triangle, created by deposition (geology), 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, res ...
s, and are often found where a
valley A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...
ed stream enters wide
flatland ''Flatland: A Romance of Many Dimensions'' is a satirical Satire is a genre of the visual arts, visual, literature, literary, and performing arts, usually in the form of fiction and less frequently Nonfiction, non-fiction, in which v ...
s or approaches the
coastal plain A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Coa ...
s around a
lake A lake is an area filled with water, localized in a Depression (geology), 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 World Ocean, oce ...
or an
ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distribution on Earth, Earth's water. An ocean can also refer to any of the ...
. They can also occur inland, on
alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but ...
s, or where a tributary stream bifurcates as it nears its
confluence In geography, a confluence (also: ''conflux'') 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 (main stem); o ...
with a larger stream. Common terms for individual river distributaries in
English-speaking countries The following is a list of English language, English-speaking population List of sovereign states, by country, including information on both First language, native speakers and second language, second-language speakers. List * The Europea ...
are ''arm'' and ''channel''.


Other names

There are a number of regional names for a stream.


Northern America

* ''Branch'' is used to name streams in Maryland and Virginia. * ''Creek'' is common throughout the United States, as well as Australia. * ''Falls'' is also used to name streams in Maryland, for streams/rivers which have waterfalls on them, even if such falls only have a small vertical drop. Little Gunpowder Falls and the
Jones Falls The Jones Falls is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed April 1, 2011 stream in Maryland. It is impounded to create Lake Roland (Maryland), Lake Roland before running thr ...
are actually rivers named in this manner, unique to Maryland. * '' Kill'' in New York,
Pennsylvania Pennsylvania (; (Pennsylvania Dutch language, Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appa ...
,
Delaware Delaware ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States, bordering Maryland to its south and west; Pennsylvania to its north; and New Jersey and the Atlantic Ocean to its east. The s ...
, and
New Jersey New Jersey is a U.S. state, state in the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. It is bordered on the north and east by the state of New York (state), New York; on the ea ...
comes from a
Dutch language Dutch ( ) is a West Germanic language spoken by about 25 million people as a first language and 5 million as a second language. It is the third most widely spoken Germanic language, after its close relatives German and English. '' Afrikaans' ...
word meaning "riverbed" or "water channel", and can also be used for the UK meaning of 'creek'. * ''Run'' in
Ohio Ohio () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Of the List of states and territories of the United States, fifty U.S. states, it is the List of U.S. states and territories by area, 34th-l ...
,
Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; ...
,
Michigan Michigan () is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the List of U.S. states and ...
, New Jersey, Pennsylvania, Virginia, or West Virginia can be the name of a stream. * ''Run'' in
Florida Florida is a U.S. state, state located in the Southeastern United States, Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia (U.S. state), Geo ...
is the name given to streams coming out of small natural springs. ''River'' is used for streams from larger springs like the Silver River and Rainbow River. * ''Stream'' and ''brook'' are used in Midwestern states, Mid-Atlantic states, and
New England New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət ...
.


United Kingdom

* ''Allt'' is used in the
Scottish Highlands The Highlands ( sco, the Hielands; gd, a’ Ghàidhealtachd , 'the place of the Gaels') is a historical region of Scotland. Culturally, the Highlands and the Scottish Lowlands, Lowlands diverged from the Late Middle Ages into the modern period ...
. * ''
Beck Beck David Hansen (born Bek David Campbell; July 8, 1970) is an American musician, singer, songwriter, and record producer. He rose to fame in the early 1990s with his Experimental music, experimental and Lo-fi music, lo-fi style, and became ...
'' is used in
Lincolnshire Lincolnshire (abbreviated Lincs.) is a Counties of England, county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-we ...
to
Cumbria Cumbria ( ) is a ceremonial counties of England, ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the ...
in areas which were once occupied by the Danes and Norwegians. * '' Bourne'' or '' winterbourne'' is used in the chalk
downland Downland, chalkland, chalk downs or just downs are areas of open chalk hills, such as the North Downs. This term is used to describe the characteristic landscape in southern England where chalk is exposed at the surface. The name "downs" is deriv ...
of southern England for ephemeral rivers. When permanent, they are '' chalk streams''. * ''Brook''. * ''Burn'' is used in Scotland and
North East England North East England is one of nine official regions of England at the first level of ITL (UK), ITL for Office for National Statistics, statistical purposes. The region has three current administrative levels below the region level in the regi ...
. * ''
Gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...
'' or ''ghyll'' is seen in the north of England and
Kent Kent is a Counties of England, county in South East England and one of the home counties. It borders Greater London to the north-west, Surrey to the west and East Sussex to the south-west, and Essex to the north across the estuary of the River ...
and
Surrey Surrey () is a ceremonial county, ceremonial and non-metropolitan county, non-metropolitan counties of England, county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant ur ...
influenced by
Old Norse Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic languages, North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and t ...
. The variant "ghyll" is used in the
Lake District The Lake District, also known as the Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous for its lakes, forests, and mountains (or ''fells''), and its associations with William Wordswort ...
and appears to have been an invention of
William Wordsworth William Wordsworth (7 April 177023 April 1850) was an English Romantic poetry, Romantic poet who, with Samuel Taylor Coleridge, helped to launch the Romanticism, Romantic Age in English literature with their joint publication ''Lyrical Balla ...
. * ''Nant'' is used in Wales. * '' Rivulet'' is a term encountered in
Victorian era In the history of the United Kingdom and the British Empire, the Victorian era was the period of Queen Victoria's reign, from 20 June 1837 until her death on 22 January 1901. The era followed the Georgian era, Georgian period and preceded ...
publications. * ''Stream'' * ''Syke'' is used in the
Scottish Lowlands The Lowlands ( sco, Lallans or ; gd, a' Ghalldachd, , place of the foreigners, ) is a cultural and historical region of Scotland. Culturally, the Lowlands and the Scottish Highlands, Highlands diverged from the Late Middle Ages into the moder ...
and Cumbria for a seasonal stream.


Other terminology

; Bar: A shoal that develops in a stream as sediment is deposited as the current slows or is impeded by wave action at the confluence. ;
Bifurcation Bifurcation or bifurcated may refer to: Science and technology * Bifurcation theory, the study of sudden changes in dynamical systems ** Bifurcation, of an incompressible flow, modeled by squeeze mapping#Fluid flow, squeeze mapping the fluid flow ...
: A fork into two or more streams. ; Channel: A depression created by constant
erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...
that carries the stream's flow. ;
Confluence In geography, a confluence (also: ''conflux'') 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 (main stem); o ...
: The point at which the two streams merge. If the two tributaries are of approximately equal size, the confluence may be called a fork. ;
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 ...
: (also known as a ''watershed'' in the United States) The area of land where water flows into a stream. A large drainage basin such as the
Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the List of rivers by discharge, largest river by Discharge (hydrology), discharge volume of water in the world, and the disputed List of river systems by length, ...
contains many smaller drainage basins. ;
Floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
: Lands adjacent to the stream that are subject to
flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study o ...
ing when a stream overflows its banks. ;
Headwaters The headwaters of a river or stream is the farthest place in that river or stream from its estuary or downstream confluence with another river, as measured along the course of the river. It is also known as a river's source. Definition The ...
or source: The part of a stream or river proximate to its source. The word is most commonly used in the plural where there is no single
point source A point source is a single identifiable ''localised'' source of something. A point source has negligible extent, distinguishing it from other source geometries. Sources are called point sources because in Mathematical model, mathematical modelin ...
. ; Knickpoint: The point on a stream's profile where a sudden change in
stream gradient Stream gradient (or stream slope) is the grade (slope), grade (or slope) of a stream measured by the ratio of drop in elevation per unit horizontal distance, usually expressed as metre, meters per kilometre, kilometer or Foot (length), feet per mile ...
occurs. ;
Mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...
: The point at which the stream discharges, possibly via an
estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
or delta, into a static body of water such as a lake or ocean. ; Pool: A segment where the water is deeper and slower moving. ;
Rapids Rapids are sections of a river where the river bed has a relatively steep stream gradient, gradient, causing an increase in water velocity and turbulence. Rapids are hydrology, hydrological features between a ''run'' (a smoothly flowing part of ...
: A
turbulent In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by Chaos theory, chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disrup ...
, fast-flowing stretch of a stream or river. ;
Riffle A riffle is a shallow landform in a flowing channel. Colloquially, it is a shallow place in a river where water flows quickly past rocks. However, in geology a riffle has specific characteristics. Topographic, sedimentary and hydraulic indica ...
: A segment where the flow is shallower and more
turbulent In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by Chaos theory, chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disrup ...
. ;
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 wate ...
: A large natural stream, which may be a
waterway A waterway is any Navigability, navigable body of water. Broad distinctions are useful to avoid ambiguity, and disambiguation will be of varying importance depending on the nuance of the equivalent word in other languages. A first distinction ...
. ; Run: A somewhat smoothly flowing segment of the stream. ; Spring: The point at which a stream emerges from an underground course through unconsolidated
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...
s or through caves. A stream can, especially with caves, flow aboveground for part of its course, and underground for part of its course. ;
Stream bed A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow (Channel (geography), channel). The lateral confines or channel margins are known as the stream Bank (geography), banks ...
: The bottom of a stream. ; Stream corridor: Stream, its floodplains, and the transitional upland fringe ;
Streamflow Streamflow, or channel runoff, is the flow of water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of E ...
: The water moving through a stream channel.:
Stream gauge A stream gauge, streamgage or stream gauging station is a location used by hydrologists or environmental scientists to monitor and test surface water, terrestrial bodies of water. hydrometry, Hydrometric measurements of water level surface elevat ...
: A site along the route of a stream or river, used for reference marking or water monitoring. ;
Thalweg In geography and fluvial geomorphology, a thalweg or talweg () is the line of lowest elevation within a valley or watercourse. Under international law, a thalweg is the middle of the primary navigable channel of a waterway that defines the bounda ...
: The river's longitudinal section, or the line joining the deepest point in the channel at each stage from source to mouth. ; Watercourse: The channel followed by a stream (a flowing body of water) or the stream itself. In the UK, some aspects of criminal law, such as the Rivers (Prevention of Pollution) Act 1951, specify that a watercourse includes those rivers which are dry for part of the year. In some jurisdictions, owners of land over which the water flows may have the legal right to use or retain some or much of that water. This right may extend to estuaries, rivers, streams,
anabranch An anabranch is a section of a river or stream that diverts from the main channel (geography), channel or main stem, stem of the watercourse and rejoins the main stem downstream. Local anabranches can be the result of small River island, islands ...
es and
canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flo ...
s. ;
Waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in several wa ...
or cascade: The fall of water where the stream goes over a sudden drop called a knickpoint; some knickpoints are formed by erosion when water flows over an especially resistant
stratum In geology and related fields, a stratum (plural, : strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separate ...
, followed by one less so. The stream expends
kinetic energy In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical sci ...
in "trying" to eliminate the knickpoint. ; Wetted perimeter: The line on which the stream's surface meets the channel walls.


Sources

A stream's source depends on the surrounding landscape and its function within larger river networks. While perennial and intermittent streams are typically supplied by smaller upstream waters and groundwater, headwater and ephemeral streams often derive most of their water from precipitation in the form of rain and snow. Most of this precipitated water re-enters the atmosphere by
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...
from soil and water bodies, or by the
evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of water to the air directly from soil, Canopy interception, ...
of plants. Some of the water proceeds to sink into the earth by infiltration and becomes groundwater, much of which eventually enters streams. Some precipitated water is temporarily locked up in snow fields and
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
s, to be released later by evaporation or melting. The rest of the water flows off the land as runoff, the proportion of which varies according to many factors, such as wind, humidity, vegetation, rock types, and relief. This runoff starts as a thin film called sheet wash, combined with a network of tiny rills, together constituting sheet runoff; when this water is concentrated in a channel, a stream has its birth. Some creeks may start from ponds or lakes.


Characteristics


Ranking

To qualify as a stream, a body of water must be either recurring or perennial. Recurring (intermittent) streams have water in the channel for at least part of the year. A stream of the first order is a stream which does not have any other recurring or perennial stream feeding into it. When two first-order streams come together, they form a second-order stream. When two second-order streams come together, they form a third-order stream. Streams of lower order joining a higher order stream do not change the order of the higher stream.


Gradient

The ''gradient'' of a stream is a critical factor in determining its character and is entirely determined by its
base level In geology and geomorphology a base level is the lower limit for an erosion, erosion process. The modern term was introduced by John Wesley Powell in 1875. The term was subsequently appropriated by William Morris Davis who used it in his cycle of ...
of erosion. The base level of erosion is the point at which the stream either enters the ocean, a lake or pond, or enters a stretch in which it has a much lower gradient, and may be specifically applied to any particular stretch of a stream. In geological terms, the stream will erode down through its bed to achieve the base level of erosion throughout its course. If this base level is low, then the stream will rapidly cut through underlying strata and have a steep gradient, and if the base level is relatively high, then the stream will form a flood plain and meander.


Meander

Meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank) and deposits sedimen ...
s are looping changes of direction of a stream caused by the erosion and deposition of bank materials. These are typically serpentine in form. Typically, over time the meanders gradually migrate downstream. If some resistant material slows or stops the downstream movement of a meander, a stream may erode through the neck between two legs of a meander to become temporarily straighter, leaving behind an arc-shaped body of water termed an ''
oxbow lake An oxbow lake is a U-shaped lake or stream pool, pool that forms when a wide meander of a river is meander cutoff, cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called ''resaca (channel), re ...
'' or ''
bayou In usage in the Southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, or simply the South) is a geographic and cultural List of regions of the United ...
''. A flood may also cause a meander to be cut through in this way.


Profile

Typically, streams are said to have a particular ''profile'', beginning with steep gradients, no flood plain, and little shifting of channels, eventually evolving into streams with low gradients, wide flood plains, and extensive meanders. The initial stage is sometimes termed a "young" or "immature" stream, and the later state a "mature" or "old" stream.


Stream load

The stream load is defined as the solid matter carried by a stream. Streams can carry sediment, or alluvium. The amount of load it can carry (capacity) as well as the largest object it can carry (competence) are both dependent on the
velocity Velocity is the directional derivative, directional speed of an physical object, object in motion as an indication of its time derivative, rate of change in position (vector), position as observed from a particular frame of reference and as m ...
of the stream.


Perennial and non-perennial


Perennial streams

A ''
perennial stream A perennial stream is a stream that has continuous flow of surface water throughout the year in at least parts of its catchment during seasons of normal rainfall, Water Supply Paper 494. as opposed to intermittent river, one whose flow is interm ...
'' is one which flows continuously all year. Water Supply Paper 494. Some perennial streams may only have continuous flow in segments of its stream bed year round during years of normal rainfall. Blue-line streams are perennial streams and are marked on topographic maps with a solid blue line.


Non-perennial streams


Ephemeral stream

Generally, streams that flow only during and immediately after precipitation are termed ''ephemeral''. There is no clear demarcation between surface runoff and an ephemeral stream, and some ephemeral streams can be classed as intermittent—flow all but disappearing in the normal course of seasons but ample flow (backups) restoring stream presence such circumstances are documented when stream beds have opened up a path into mines or other underground chambers. According to official U.S. definitions, the channels of intermittent streams are well-defined, as opposed to ephemeral streams, which may or may not have a defined channel, and rely mainly on storm runoff, as their aquatic bed is above the
water table The water table is the upper surface of the Phreatic zone, zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is ...
. An ephemeral stream does not have the biological, hydrological, and physical characteristics of a continuous or intermittent stream. The same non-perennial channel might change characteristics from intermittent to ephemeral over its course.


Intermittent or seasonal stream

Washes can fill up quickly during rains, and there may be a sudden torrent of water after a
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms ...
begins upstream, such as during
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in Atmosphere of Earth, atmospheric circulation and precipitation associated with annu ...
al conditions. In the United States, an ''intermittent'' or ''seasonal stream'' is one that only flows for part of the year and is marked on topographic maps with a line of blue dashes and dots. A ''
wash WASH (or Watsan, WaSH) is an acronym that stands for "Water supply, water, sanitation and hygiene". It is used widely by non-governmental organizations and Aid agency, aid agencies in Developing country, developing countries. The purposes of prov ...
,'' ''desert wash, or arroyo'' is normally a dry streambed in the
desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one ...
s of the
American Southwest The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ...
, which flows after sufficient rainfall. In Italy, an intermittent stream is termed a torrent ( it, torrente). In full flood the stream may or may not be "torrential" in the dramatic sense of the word, but there will be one or more seasons in which the flow is reduced to a trickle or less. Typically torrents have Apennine rather than Alpine sources, and in the summer they are fed by little precipitation and no melting snow. In this case the maximum discharge will be during the spring and autumn. An intermittent stream can also be called a winterbourne in Britain or a
wadi Wadi ( ar, وَادِي, wādī), alternatively ''wād'' ( ar, وَاد), North African Arabic Oued, is the Arabic term traditionally referring to a valley. In some instances, it may refer to a wet ( ephemeral) riverbed that contains water ...
in the
Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...
-speaking world. In Australia, an intermittent stream is usually called a creek and marked on topographic maps with a solid blue line.


Drainage basins

The extent of land basin drained by a stream is termed its drainage basin (also known in North America as the watershed and, in British English, as a catchment). A basin may also be composed of smaller basins. For instance, the
Continental Divide A continental divide is a drainage divide A drainage divide, water divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topograph ...
in North America divides the mainly easterly-draining Atlantic Ocean and Arctic Ocean basins from the largely westerly-flowing Pacific Ocean basin. The Atlantic Ocean basin, however, may be further subdivided into the Atlantic Ocean and Gulf of Mexico drainages. (This delineation is termed the
Eastern Continental Divide The Eastern Continental Divide, Eastern Divide or Appalachian Divide is a drainage divide, hydrographic divide in eastern North America that separates the easterly Atlantic Seaboard drainage basin, watershed from the westerly Gulf of Mexico wat ...
.) Similarly, the Gulf of Mexico basin may be divided into the
Mississippi River The Mississippi River is the List of longest rivers of the United States (by main stem), second-longest river and chief river of the second-largest Drainage system (geomorphology), drainage system in North America, second only to the Hudson B ...
basin and several smaller basins, such as the
Tombigbee River The Tombigbee River is a tributary of the Mobile River, approximately 200 mi (325 km) long, in the U.S. states of Mississippi Mississippi () is a U.S. state, state in the Southeastern United States, Southeastern region of the Uni ...
basin. Continuing in this vein, a component of the Mississippi River basin is the
Ohio River The Ohio River is a long river in the United States. It is located at the boundary of the Midwestern United States, Midwestern and Southern United States, flowing southwesterly from western Pennsylvania to its river mouth, mouth on the Mississip ...
basin, which in turn includes the Kentucky River basin, and so forth.


Crossings

Stream crossings are where streams are crossed by
road A road is a linear way for the conveyance of traffic that mostly has an road surface, improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are ro ...
s, pipelines,
railways Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in Track (rail transport), tracks. In contrast to road transport, where the ...
, or any other thing which might restrict the flow of the stream in ordinary or flood conditions. Any structure over or in a stream which results in limitations on the movement of fish or other ecological elements may be an issue.


See also

*
Aqueduct (water supply) An aqueduct is a watercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the term ''aqueduct'' is used for any system of pipes, ditches, canals, tunnels, and other structures used for this p ...
* Environmental flow * Head cut * Playfair's Law *
River ecosystem River ecosystems are flowing waters that drain the landscape, and include the Biotic component, biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its man ...
*
Rock-cut basin A rock-cut basin is a natural cylindrical depression cut into stream or river beds, often filled with water. Such plucked-bedrock pits are created by kolk (vortex), kolks; powerful vortices within the water currents which spin small boulders around ...


References


External links


Glossary of stream-related terms
StreamNet {{Authority control Bodies of water Fluvial landforms Geomorphology Hydrology Rivers