rivulet n : a small stream [syn: rill, run, runnel, streamlet]

English

Etymology

From the Old French riveret, little stream

Noun

rivulet (plural: rivulets)

1. A small brook or stream; a streamlet

   A rivulet of tears ran down his face.

Translations

• Greek: ποταμάκι

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.

Types of stream

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

• Beck is used in Yorkshire, Lancashire and Cumbria.
• Bourne is used in the chalk downland of southern England
• Brook is used in the Midlands.
• Burn is used in Scotland and North East England.
• Stream is limited to Southern England.
• Syke is used in lowland Scotland and Cumbria.

In North America:

• Bourn in Cascadia refers mostly to wide but relatively short, stilly streams with broad, rocky and gravelly beaches/banks, uneven bottoms very deep in some places but dappled with small, rocky aights, with uncommonly clear water except for adjascent pools filled with debris and plantlife in which fishes and amphibians spawn. Often a distributary of a river and a tributary of a coastal or lakeside marsh, or, somewhat less frequently, an "independent" (not especially near a lake or ocean) swamp or other wetland.
• Kill in New York, Pennsylvania, Delaware, and New Jersey comes from a Dutch language word, as in Peekskill (NY), Fishkill (NY), Broadkill (DE), Schuylkill (PA) and Fresh Kills.
• Run in Ohio, Pennsylvania, Maryland, or Virginia can be the name of a stream, as in Bull Run or Difficult Run.
• Branch, fork, or prong can refer to tributaries or distributaries that share the same name as the main stream, generally with the addition of a cardinal direction (i.e., "Bone River, North Fork").

Parts of a stream

; Source: The spring from which the stream originates, or other point of origin of a stream.; 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.; Pool: A segment where the water is deeper and slower moving.; Channel: A depression created by constant erosion, that carries the stream's flow.; Stream bed: The bottom of a stream.; Thalweg: The river's longitudinal section, or the line joining the deepest point in the channel at each stage from source to mouth.; Nickpoint: The point on a stream's profile where a sudden change in stream gradient occurs.; 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.

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.

Characteristics of streams

; 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.

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 in 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 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.

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.) 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.

See also

• Arroyo
• Bayou
• Body of water
• Burn
• Chalk stream
• Lake
• Lotic system ecology
• Marsh
• Ocean
• Perennial stream
• River
• Rock-cut basin
• Swamp
• Wadi
• Waterway

References

adolescent stream, arroyo, beck, bourn, braided stream, branch, brook, brooklet, burn, channel, creek, crick, flowing stream, fluviation, fresh, freshet, gill, kill, lazy stream, meandering stream, midchannel, midstream, millstream, moving road, navigable river, race, racing stream, river, run, rundle, runlet, runnel, sike, spill stream, stream, stream action, streamlet, subterranean river, wadi, watercourse, waterway