Stream
[2] The stream encompasses surface, subsurface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls.
[3] Streams are important as conduits in the water cycle, instruments in groundwater recharge, and corridors for fish and wildlife migration.
Given the status of the ongoing Holocene extinction, streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity.
The study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography.
[19] A river is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a navigable waterway.
Distributaries are common features of river deltas, and are often found where a valleyed stream enters wide flatlands or approaches the coastal plains around a lake or an ocean.
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.
The majority of the water flows as a runoff from the ground; the proportion of this varies depending on several factors, such as climate, temperature, vegetation, types of rock, and relief.
Using the model for comparison in two basins in Tibet (Helongqu and Niyang River White Water), the results show that the critical support flow (Qc) of the housing dragon song[clarification needed] is 0.0028 m3/s.
Meanders are looping changes of direction of a stream caused by the erosion and deposition of bank materials.
[55] 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.
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.
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.
"Macroinvertebrate" refers to easily seen invertebrates, larger than 0.5 mm, found in stream and river bottoms.
[58] Macroinvertebrates are larval stages of most aquatic insects and their presence is a good indicator that the stream is perennial.
Larvae of caddisflies, mayflies, stoneflies, and damselflies[59] require a continuous aquatic habitat until they reach maturity.
Crayfish and other crustaceans, snails, bivalves (clams), and aquatic worms also indicate the stream is perennial.
Fish will seek cover if alerted to human presence, but should be easily observed in perennial streams.
Frogs and tadpoles usually inhabit shallow and slow moving waters near the sides of stream banks.
[60] Well defined river beds composed of riffles, pools, runs, gravel bars, a bed armor layer, and other depositional features, plus well defined banks due to bank erosion, are good identifiers when assessing for perennial streams.
Another perennial stream indication is an abundance of red rust material in a slow-moving wetted channel or stagnant area.
This is evidence that iron-oxidizing bacteria are present, indicating persistent expression of oxygen-depleted ground water.
In the adjacent overbank of a perennial stream, fine sediment may cling to riparian plant stems and tree trunks.
Organic debris drift lines or piles may be found within the active overbank area after recent high flow.
They defend against floods, remove contaminants, recycle nutrients that are potentially dangerous as well as provide food and habitat for many forms of fish.
