Perennial stream


Perennial stream

A perennial stream or perennial river is a stream or river (channel) that has continuous flow in parts of its bed all year round during years of normal rainfall. "Perennial" streams are contrasted with "intermittent" streams which normally cease flowing for weeks or months each year, and with "ephemeral" channels that flow only for hours or days following rainfall. During unusually dry years, a normally perennial stream may cease flowing, becoming intermittent for days, weeks, or months depending on severity of the drought. The boundaries between perennial, intermittent, and ephemeral channels are indefinite, and subject to a variety of identification methods adopted by local governments, academics, and others with a need to classify stream-flow permanence.

As stream-flow decreases in dry weather, visible flow above the stream bed may not be readily evident, especially in streams with coarse substrate (gravel and rocks), where water is flowing beneath and between these particles (hyporheic flow). From a biological perspective, a stream may be considered flowing if sufficient water is available to support flow-dependent aquatic life, including fish and gill-breathing amphibians, benthic insects, crustaceans, and mollusks, many of which survive in shallow hyporheic flow beneath rocks or logs. This extreme low flow may not be detectable on typical USGS stream-flow gages, but is vital to stream ecology.cite web | url = http://www.osmre.gov/coalex/coalex97.htm | title = Definition of "Perennial Stream" | publisher = Office of Surface Mining - US Department of the Interior | accessdate = March 28 | accessyear = 2007]

ee also

* winterbourne, a stream or river that flows only in winter.

References



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Look at other dictionaries:

  • perennial stream —    A stream or reach of a stream that flows continuously throughout the year and whose surface is generally lower than the water table adjacent to the region adjoining the stream.    Compare: ephemeral stream, intermittent stream.    GG …   Glossary of landform and geologic terms

  • perennial stream — small river which flows throughout the year …   English contemporary dictionary

  • Perennial (disambiguation) — Perennial is a commonly used adjective with several meanings relating to yearly activity; see the formal dictionary definition . More specifically, perennial may refer to:* Perennial plant, a plant which lives for more than two growing seasons,… …   Wikipedia

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  • perennial — 1. adjective /pəˈɹɛniəl/ a) Lasting or remaining active throughout the year, or all the time. a perennial stream b) (of a plant) Having a life cycle of more than two years. Compare , . The perennial existence of bodies corporate and their… …   Wiktionary

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  • perennial — perenniality, n. perennially, adv. /peuh ren ee euhl/, adj. 1. lasting for an indefinitely long time; enduring: her perennial beauty. 2. (of plants) having a life cycle lasting more than two years. 3. lasting or continuing throughout the entire… …   Universalium

  • perennial — adjective 1》 lasting for a long time; enduring or continually recurring.     ↘continually engaged in a specified activity: a perennial student. 2》 (of a plant) living for several years. Compare with annual, biennial. 3》 (of a stream or spring)… …   English new terms dictionary

  • perennial — adj. & n. adj. 1 lasting through a year or several years. 2 (of a plant) lasting several years (cf. ANNUAL). 3 lasting a long time or for ever. 4 (of a stream) flowing through all seasons of the year. n. a perennial plant (a herbaceous perennial) …   Useful english dictionary

  • perennial — per•en•ni•al [[t]pəˈrɛn i əl[/t]] adj. 1) lasting for an indefinitely long time; enduring 2) bot (of plants) having a life cycle lasting more than two years 3) lasting or continuing throughout the entire year, as a stream 4) perpetual; recurrent… …   From formal English to slang


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