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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 pre ...
flowing within the bed and
bank A bank is a financial institution that accepts Deposit account, 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 m ...
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 ...
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 t ...
(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 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). 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 co ...
, 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 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. Given the status of the ongoing Holocene extinction, streams play an important
corridor Corridor or The Corridor may refer to: Arts, entertainment, and media Films * ''The Corridor'' (1968 film), a 1968 Swedish drama film * ''The Corridor'' (1995 film), a 1995 Lithuanian drama film * ''The Corridor'' (2010 film), a 2010 Canadia ...
role in connecting
fragmented habitat Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological process ...
s 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 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 call ...
'' and is a core element of environmental geography.


Types


Brook

A stream smaller than a creek, especially one that is fed by a
spring Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a h ...
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 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 to ...
,
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 smaller islands. It is the sixth-largest island coun ...
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 continental mainland. It comprises England, Scotland, Wales and ...
,
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 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 t ...
,
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 ...
, a tidal inlet, 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 saltwater or brackish water that is regularly flooded by the tides. It is domin ...
or mangrove swamp, 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. Thro ...
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 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 ...
is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a navigable
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 drai ...
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 na ...
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 wor ...
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. 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 ove ...
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 wor ...
. They can also occur inland, on alluvial fans, 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 E ...
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 The Gunpowder River is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed April 1, 2011 tidal inlet on the western side of Chesapeake Bay in Maryland, United States. It is formed by the ...
and the Jones Falls are actually rivers named in this manner, unique to Maryland. * '' Kill'' in New York,
Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
,
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 Delawa ...
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 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 t ...
,
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 t ...
, New Jersey, Pennsylvania, Virginia, or West Virginia can be the name of a stream. * ''Run'' in
Florida Florida is a state located in the 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, to the east by the Bahamas and Atlantic Ocean, and ...
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 ...
.


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 S ...
. * '' Beck'' 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 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. ...
in areas which were once occupied by the Danes and Norwegians. * '' Bourne'' or '' winterbourne'' is used in the chalk downland of southern England for ephemeral rivers. When permanent, they are ''
chalk streams Chalk streams are rivers that rise from springs in landscapes with chalk bedrock. Since chalk is permeable, water percolates easily through the ground to the water table and chalk streams therefore receive little surface runoff. As a result, t ...
''. * ''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 for statistical purposes. The region has three current administrative levels below the region level in the region; combined authority, unitary author ...
. * ''
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 Kent is a 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 Thames; it faces ...
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 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 Edwa ...
publications. * ''Stream'' * ''Syke'' is used in the Scottish Lowlands 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: A fork into two or more streams. ; Channel: 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 d ...
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 largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...
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 hydrol ...
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 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 environm ...
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, fast-flowing stretch of a stream or river. ; Riffle: A segment where the flow is shallower and more turbulent. ;
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 ...
: 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 Spring(s) may refer to: Common uses * Spring (season), a season of the year * Spring (device), a mechanical device that stores energy * Spring (hydrology), a natural source of water * Spring (mathematics), a geometric surface in the shape of a h ...
: 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 transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...
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). The lateral confines or channel margins are known as the stream banks or river banks, during all but fl ...
: The bottom of a stream. ; Stream corridor: Stream, its floodplains, and the transitional upland fringe ; Streamflow: The water moving through a stream channel.: Stream gauge: A site along the route of a stream or river, used for reference marking or water monitoring. ; Thalweg: 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 f ...
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 ...
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 acce ...
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. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transp ...
of plants. Some of the water proceeds to sink into the earth by
infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...
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 a ...
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 In mathematics and other formal sciences, first-order or first order most often means either: * "linear" (a polynomial of degree at most one), as in first-order approximation and other calculus uses, where it is contrasted with "polynomials of hi ...
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 ban ...
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''. 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 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 i ...
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 In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but histori ...
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 some ...
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 oscil ...
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,'' ''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 on ...
s of the American Southwest, 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 Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National P ...
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 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 A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not c ...
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 spans ...
.) 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 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 ...
basin, which in turn includes the
Kentucky River The Kentucky River is a tributary of the Ohio River, long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed June 13, 2011 in the U.S. Commonwealth of Kentucky. The river and its t ...
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 o ...
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 prep ...
, 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 ...
* Environmental flow * Head cut * Playfair's Law *
River ecosystem River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts.Angelier, ...
* Rock-cut basin


References


External links


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