Stream

From Wikipedia, the free encyclopedia

For other uses, see Stream (disambiguation).
Butchers Creek, Omeo, Victoria, Australia.
Butchers Creek, Omeo, Victoria, Australia.

A stream, brook, beck, burn, creek, crick, kill, lick, rill, syke, bayou, rivulet, or run is a body of water with a current, confined within a bed and stream-banks. Streams are important as conduits in the water cycle, instruments in groundwater recharge, 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 event, streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity. Stream is also an umbrella term used in the scientific community for all flowing natural waters, regardless of size. The study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography.

Creeks are the site of recreation as well.
Creeks are the site of recreation as well.

Contents

[edit] Types of stream

An Australian creek.
An Australian creek.
River
A large natural stream, which may be a waterway.
Creek (North America and Australia)
A small to medium sized natural stream. Sometimes navigable by motor craft and may be intermittent. In some dialects it is pronounced: "crick".
Creek (UK and India)
A tidal inlet, typically in a saltmarsh or mangrove swamp. Alternatively, between enclosed and drained, former saltmarshes or swamps. In these cases, the stream is the tidal stream, the course of the seawater through the creek channel at low and high tide.
Tributary
A contributory stream, or a stream which does not reach the sea but joins another river (a parent river). Sometimes also called a branch or fork.
Brook
A stream smaller than a creek, especially one that is fed by a spring or seep. It is usually small and easily forded. A brook is characterized by its shallowness and its bed being composed solely of rocks.

[edit] Other names for streams

Yellow River in rural Indiana, USA. Rivers of this size are often referred to as "creeks."
Yellow River in rural Indiana, USA. Rivers of this size are often referred to as "creeks."
A rocky stream in Hawaii
A rocky stream in Hawaii
A brook in the Bay of Fundy, Nova Scotia, Canada
A brook in the Bay of Fundy, Nova Scotia, Canada
Ambro torrent, Italy.
Ambro torrent, Italy.

In the United Kingdom, there are several regional names for a stream:

In North America:

[edit] Parts of a 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.
Source
The spring from which the stream originates, or other point of origin of a stream.
Headwaters
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.
Confluence
The point at which the two streams merge. If the two tributaries are of approximately equal size, the confluence may be called a fork.
Run
A somewhat smoothly flowing segment of the stream.
Pool
A segment where the water is deeper and slower moving.
Riffle
A segment where the flow is shallower and more turbulent.
Channel
A depression created by constant erosion, that carries the stream's flow.
Floodplain
Lands adjacent to the stream that are subject to flooding when a stream overflows its banks.
Stream bed
The bottom of a stream.
Gauging station
A point of demarkation 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.
Wetted perimeter
The line on which the stream's surface meets the channel walls.
Nickpoint
The point on a stream's profile where a sudden change in stream gradient occurs.
Waterfall or cascade
The fall of water where the stream goes over a sudden drop called a nickpoint; some nickpoints are formed by erosion when water flows over an especially resistant stratum, followed by one less so. The stream expends kinetic energy in "trying" to eliminate the nickpoint.
Mouth
The point at which the stream discharges, possibly via an estuary or delta, into a static body of water such as a lake or ocean.

[edit] Sources of stream water

Streams typically derive most of their water from precipitation in the form of rain and snow. Most of this water re-enters the atmosphere by evaporation 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 glaciers, 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.

[edit] Characteristics of streams

Tämnarån, Sweden.
Tämnarån, Sweden.
Ranking 
Streams in geographic terms are awarded order designations. A stream of the first order is a blue-line stream which does not have any other blue-line stream feeding into it. A stream of the second order is one which is formed by the joining of two or more blue-line streams. A third-order stream is one below the confluence of two or more second-order streams; a fourth-order stream is formed by the confluence of at least two third-order streams, and so forth.
Gradient 
The gradient of a stream is a critical factor in determining its character, and is entirely determined by its base level 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 geologic 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 meanders.
Stream in North Bay, Ontario, Canada
Stream in North Bay, Ontario, Canada
Meander 
Meanders are looping changes of direction of a stream caused by the erosion and deposition of bank materials. These may be somewhat sine-wave in form. Typically, over time, the meanders don't disappear but 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 or bayou. A flood may also result in a meander being 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. However, a stream may meander for some distance before falling into a "young" stream condition.

[edit] Intermittent and ephemeral streams

An Australian creek, low in the dry season, carrying little water. The energetic flow of the stream had, in flood, moved finer sediment further downstream. There is a pool to lower right and a riffle to upper left of the photograph.
An Australian creek, low in the dry season, carrying little water. The energetic flow of the stream had, in flood, moved finer sediment further downstream. There is a pool to lower right and a riffle to upper left of the photograph.

In the United States, an intermittent 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 or desert wash is normally a dry streambed in the deserts of the American Southwest which flows only after significant rainfall. Washes can fill up quickly during rains, and there may be a sudden torrent of water after a thunderstorm begins upstream, such as during monsoonal conditions. These flash floods often catch travellers by surprise. An intermittent stream can also be called an arroyo in Latin America, a winterbourne in Britain, or a wadi in the Arabic-speaking world.

In Italy an intermittent stream is termed a torrent (Italian 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 Appenine rather than Alpine sources, and in the summer are fed by little precipitation and no melting snow. In this case the maximum discharge will be during the spring and autumn. However there are also glacial torrents with a different seasonal regime.

A blue-line stream is one which flows for most or all of the year and is marked on topographic maps with a solid blue line. In Australia, an intermittent stream is usually called a creek, and marked on topographic maps with a solid blue line.

Generally, streams that flow only during and immediately after precipitation are termed ephemeral. There is no clear demarkation between surface runoff and ephemeral stream.

[edit] Drainage basins

Oyster Creek (Sugar Creek) in Sugar Land, Texas
Oyster Creek (Sugar Creek) in Sugar Land, Texas

The extent of land basin drained by a stream is termed its drainage basin (also known in North America as the watershed[1] 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.) Similarly, the Gulf of Mexico basin may be divided into the Mississippi River basin and a number of smaller basins, such as the Tombigbee River basin. Continuing in this vein, a component of the Mississippi River basin is the Ohio River basin, which in turn includes the Kentucky River basin, and so forth.

[edit] See also

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[edit] References

  1. ^ In British English, however, a watershed is the dividing line between drainage basins, in other words a water divide