A stream is a continuous body of surface waterflowing within the bed and banks 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 rivers, 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 (from precipitation or meltwater), daylightedsubterranean water, and surfaced groundwater (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.
A river is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a navigablewaterway.
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.
A tributary is a contributory stream to a larger stream, or a stream which does not reach a static body of water such as a lake, bay or ocean but joins another river (a parent river). Sometimes also called a branch or fork.
There are a number of regional names for a stream.
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.
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.
The river's longitudinal section, or the line joining the deepest point in the channel at each stage from source to mouth.
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, anabranches and canals.
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, followed by one less so. The stream expends kinetic energy in "trying" to eliminate the knickpoint.
The line on which the stream's surface meets the channel walls.
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 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. Some creeks may start from ponds or lakes.
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.
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 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.
Meanders 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 or bayou. A flood may also cause a meander to be cut through in this way.
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.
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 of the stream.
Perennial and non-perennial
A perennial stream is one which flows continuously all year.: 57 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.
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,: 58 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. 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.
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. 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.: 57–58 A wash,desert wash, or arroyo is normally a dry streambed in the deserts of the American Southwest, which flows after sufficient rainfall.
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 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, a wadi in the Arabic-speaking world or torrente or rambla (this last one from arabic origin) in Spain and Latin America. In Australia, an intermittent stream is usually called a creek and marked on topographic maps with a solid blue line.
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.) Similarly, the Gulf of Mexico basin may be divided into the Mississippi River 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 basin, which in turn includes the Kentucky River basin, and so forth.
Stream crossings are where streams are crossed by roads, pipelines, railways, 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.
^Langbein, W.B.; Iseri, Kathleen T. (1995). "Hydrologic Definitions: Stream". Manual of Hydrology: Part 1. General Surface-Water Techniques (Water Supply Paper 1541-A). Reston, VA: USGS. Archived from the original on 2012-05-09.
^Alexander, L. C., Autrey, B., DeMeester, J., Fritz, K. M., Golden, H. E., Goodrich, D. C., ... & McManus, M. G. (2015). Connectivity of streams and wetlands to downstream waters: review and synthesis of the scientific evidence (Vol. 475). EPA/600/R-14.
^"creek". oxforddictionaries.com. Oxford University Press. Archived from the original on September 24, 2016. Retrieved 18 May 2019. British...especially an inlet...(whereas) NZ, North American, Australian...stream or minor tributary.
^"(US) creek". English Oxford Living Dictionaries. Oxford University Press. Archived from the original on September 24, 2016. Retrieved 18 May 2019. North American, Australian, NZ...A stream, brook, or minor tributary of a river.
^"creek". Dictionary.com. Dictionary.com, LLC. Retrieved 18 May 2019. U.S., Canada , and Australia…a stream smaller than a river.
^Steigerwalt, Nancy M.; Cichra, Charles E.; Baker, Shirley M. (2008). "Composition and Distribution of Aquatic Invertebrate Communities on Snags in a North Central Florida, USA, Spring-Run Stream". Florida Scientist. 71 (3): 273–286. JSTOR24321406.
^Black Creek (Susquehanna River)#Hydrology and climate, 'Black Creek is an ephemeral stream. It used to drain an area between Turtle Creek and the Susquehanna River, but now loses its flow to underground mines via broken bedrock. Its channel is also disrupted by strip mines and rock piles.', 14 Nov 2016.
^Langbein, W.B.; Iseri, Kathleen T. (1995). "Hydrologic Definitions: Watershed". Manual of Hydrology: Part 1. General Surface-Water Techniques (Water Supply Paper 1541-A). Reston, VA: USGS. Archived from the original on 2012-05-09.
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