
A stream is a continuous
body
Body may refer to:
In science
* Physical body, an object in physics that represents a large amount, has mass or takes up space
* Body (biology), the physical material of an organism
* Body plan, the physical features shared by a group of anima ...
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 p ...
flowing within the
bed
A bed is an item of furniture that is used as a place to sleep, rest, and relax.
Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many 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.
Because ...
s of a
channel
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
. 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 w ...
s, while smaller, less voluminous and more
intermittent 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 ...
(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, sleet, snow, ice pellets, graupel and hail. ...
or
meltwater),
daylighted subterranean water, and surfaced
groundwater (
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 fr ...
). 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 moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs ...
, and corridors for fish and wildlife migration. The biological
habitat in the immediate vicinity of a stream is called a
riparian zone. 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, fis ...
, streams play an important
corridor role in connecting
fragmented habitats and thus in conserving
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species (''species diversity''), and ecosystem ('' ecosystem diversity'' ...
. The study of streams and
waterway
A waterway is any 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 is necessary ...
s in general is known as ''surface
hydrology'' 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,
Canada
Canada is a country in North America. Its 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's second-largest country by total ...
,
New Zealand and the
United States, 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,
India, and parts of
Maryland
Maryland ( ) is a state in the 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; and Delaware and the Atlantic Ocean to ...
,
New England
New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces of ...
, a
tidal
Tidal is the adjectival form of tide.
Tidal may also refer to:
* ''Tidal'' (album), a 1996 album by Fiona Apple
* Tidal (king), a king involved in the Battle of the Vale of Siddim
* TidalCycles, a live coding environment for music
* Tidal (servic ...
inlet, typically in a
salt marsh 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 mangroves cannot withstand fr ...
, or between enclosed and drained former salt marshes or swamps (e.g.
Portsbridge Creek
Portsbridge Creek, also known as Portcreek, Portsea Creek, Canal Creek and Ports Creek, is a tidal waterway just off the southern coast of England that runs between Portsea Island and the mainland from Langstone Harbour to Tipner Lake. Throug ...
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 ...
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 appro ...
through the
creek
A creek in North America and elsewhere, such as Australia, is a stream that is usually smaller than a river. In the British Isles it is a small tidal inlet.
Creek may also refer to:
People
* Creek people, also known as Muscogee, Native Americans
...
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 w ...
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 di ...
waterway
A waterway is any 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 is necessary ...
.
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 ...
is a contributory stream to a larger stream, or a stream which does not reach a static
body of water such as 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 ...
,
bay
A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a ...
or
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 worl ...
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 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 (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 distributaries) which then continue downstream. Some rivers form complex networks of distributaries, typi ...
. Distributaries are common features of
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 rare ...
s, and are often found where a
valley
A valley is an elongated low area often running between hills or 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 or streams over ...
ed stream enters wide
flatlands or approaches the
coastal plains around 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 ...
or an
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 worl ...
. 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 a ...
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-speaking population by country, including information on both native speakers and second-language speakers.
List
* The European Union is a supranational union composed of 27 member states. The total ...
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 are actually rivers named in this manner, unique to Maryland.
* ''
Kill'' in
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
,
Pennsylvania
Pennsylvania (; (Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions of the United States. It borders Delaware to ...
,
Delaware
Delaware ( ) is a state in the 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 state takes its name from the adjacent ...
, and
New Jersey
New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware R ...
comes from a
Dutch language word meaning "riverbed" or "water channel", and can also be used for the UK meaning of 'creek'.
* ''Run'' in
Ohio,
Maryland
Maryland ( ) is a state in the 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; and Delaware and the Atlantic Ocean to ...
,
Michigan
Michigan () is a state in the Great Lakes region of the upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the 10th-largest state by population, the 11th-largest by area, and the l ...
, New Jersey, Pennsylvania, Virginia, or West Virginia can be the name of a stream.
* ''Run'' in
Florida 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
The Rainbow River is located in Dunnellon, Florida, United States, in the southwest corner of Marion County, about southwest of Ocala, northwest of Orlando and north of the Tampa Bay area. It is formed by a first-magnitude spring ( Rainbow ...
.
* ''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, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York to the west and by the Canadian provinces of ...
.
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 Lowlands diverged from the Late Middle Ages into the modern period, when Lowland Sco ...
.
* ''
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 and lo-fi style, and became known for creating musical collag ...
'' is used in
Lincolnshire to
Cumbria
Cumbria ( ) is a 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 Local Government Act 1972. Cumb ...
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.
* ''
Gill
A gill () is a respiratory organ that many 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 respiration on land provided they ar ...
'' or ''ghyll'' is seen in the north of England and
Kent and
Surrey
Surrey () is a ceremonial and non-metropolitan county in South East England, bordering Greater London to the south west. Surrey has a large rural area, and several significant urban areas which form part of the Greater London Built-up Area. ...
influenced by
Old Norse
Old Norse, Old Nordic, or Old Scandinavian, is a stage of development of North Germanic dialects before their final divergence into separate Nordic languages. Old Norse was spoken by inhabitants of Scandinavia and their overseas settlement ...
. The variant "ghyll" is used in the
Lake District and appears to have been an invention of
William Wordsworth
William Wordsworth (7 April 177023 April 1850) was an English Romantic poet who, with Samuel Taylor Coleridge, helped to launch the Romantic Age in English literature with their joint publication '' Lyrical Ballads'' (1798).
Wordsworth's ' ...
.
* ''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 period and preceded the Edwardian ...
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 Highlands diverged from the Late Middle Ages into the modern period, when L ...
and Cumbria for a seasonal stream.
Other terminology
;
Bar
Bar or BAR may refer to:
Food and drink
* Bar (establishment), selling alcoholic beverages
* Candy bar
* Chocolate bar
Science and technology
* Bar (river morphology), a deposit of sediment
* Bar (tropical cyclone), a layer of cloud
* 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 the fluid flow
* River bifurcation, the for ...
: A fork into two or more streams.
;
Channel
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
: A depression created by constant
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
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, the ...
: (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 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 ( 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 of the discipline hydrolo ...
ing when a stream overflows its banks.
[
]
;
Headwaters 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.
;
Knickpoint: The point on a stream's profile where a sudden change in
stream gradient Stream gradient (or stream slope) is the grade (or slope) of a stream measured by the ratio of drop in elevation per unit horizontal distance, usually expressed as meters per kilometer or feet per mile.
Hydrology and geology
A high gradient indic ...
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 ...
: 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: A
turbulent
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by 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 disruption between ...
, 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 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 disruption between ...
.
;
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 ...
: A large natural stream, which may be a
waterway
A waterway is any 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 is necessary ...
.
; Run: A somewhat smoothly flowing segment of the stream.
;
Spring: The point at which a stream emerges from an underground course through unconsolidated
sediments 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). The lateral confines or channel margins are known as the stream banks or river banks, during all but flood ...
: 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 in streams and other channels, and is a major element of the water cycle. It is one component of the movement of water from the land to waterbodies, the other component being surface runoff. Wate ...
: 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 terrestrial bodies of water. Hydrometric measurements of water level surface elevation (" stage") and/or vo ...
: 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 bo ...
: 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 or stem of the watercourse and rejoins the main stem downstream. Local anabranches can be the result of small islands in the watercourse. In larger anabranches, ...
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 flow un ...
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 ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...
, followed by one less so. The stream expends
kinetic energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its accel ...
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 humidi ...
from soil and water bodies, or by the
evapotranspiration 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 over many years, often centuries. It acquires distinguishing features, such as ...
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 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 erosion ...
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 of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank) and deposits sediments on an inner, convex ba ...
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 pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are call ...
'' or ''
bayou
In usage in the Southern United States, a bayou () is a body of water typically found in a flat, low-lying area. It may refer to an extremely slow-moving stream, river (often with a poorly defined shoreline), marshy lake, wetland, or creek. They ...
''. 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 {{page numbers needed, date=November 2020
Stream load is a geologic term referring to the solid matter carried by a stream (Strahler and Strahler, 2006). Erosion and bed shear stress continually remove mineral material from the bed and banks of ...
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 speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is ...
of the stream.
Perennial and non-perennial
Perennial streams
A ''
perennial stream'' 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 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 saturated.
T ...
.
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 acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are so ...
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 atmospheric circulation and precipitation associated with annual latitudinal oscill ...
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, sanitation and hygiene". It is used widely by non-governmental organizations and aid agencies in developing countries. The purposes of providing access to WASH services include achi ...
,'' ''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, New Mexico, and adjacent portions of California, Colorado, N ...
, 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 onl ...
in the Arabic
Arabic (, ' ; , ' or ) is a 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. E.Watson; Walter ...
-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 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 hydrographic divide in eastern North America that separates the easterly Atlantic Seaboard watershed from the westerly Gulf of Mexico watershed. The divide nearly spa ...
.) Similarly, the Gulf of Mexico basin may be divided into 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 ...
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 and Alabama. Together with the Alabama, it merges to form the short Mobile River before the latter empties int ...
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 and Southern United States, flowing southwesterly from western Pennsylvania to its mouth on the Mississippi River at the southern tip of Illinoi ...
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 improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation.
There are many types of ...
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 tracks. In contrast to road transport, where the vehicles run on a pre ...
, 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)
* Environmental flow
* Head cut
* Playfair's Law
* River ecosystem
* Rock-cut basin
References
External links
Glossary of stream-related terms
StreamNet
{{Authority control
Bodies of water
Fluvial landforms
Geomorphology
Hydrology
Rivers