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A stream pool, in
hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
, is a stretch of a
river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
or
stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
in which the water depth is above average and the water velocity is below average.


Formation

A stream pool may be bedded with
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
or
armoured Armour (British English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or f ...
with
gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...
, and in some cases the pool formations may have been formed as basins in exposed
bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...
formations.
Plunge pool A plunge pool (or plunge basin or waterfall lake) is a deep depression in a stream bed at the base of a waterfall or Shut-in (river), shut-in. It is created by the erosion, erosional forces of cascading water on the rocks at formation's base wher ...
s, or plunge basins, are stream pools formed by the action of
waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in several wa ...
s. Pools are often formed on the outside of a bend in a meandering river.


Dynamics

The depth and lack of water velocity often leads to stratification in stream pools, especially in warmer regions. In warm arid regions of the Western United States, surface waters were found to be 3-9 °C higher than those at the bottom


Habitat

This portion of a stream often provides a specialized
aquatic ecosystem An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms that are dependent on each other and on their environment. The t ...
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
for
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s that have difficulty feeding or navigating in swifter reaches of the stream or in seasonally warmer water. Such pools can be important for fish habitat, especially where many streams reach high summer temperatures and very low-flow dry season characteristics. In warm and arid regions, the stratification of stream pools provide cooler water for fish that prefer low water temperatures such as the redband trout (''Oncorhynchus mykiss'') in the Western United States. Mosquito larvae, which prefer still and often stagnant water, can be found in stream pools due to the low water velocity.


See also

*
Pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from th ...
*
Reach (geography) A reach is a segment of a stream, river, or arm of the sea, usually suggesting a straight, level, uninterrupted stretch. They are traditionally defined by the capabilities of sailing boats, as a stretch of a watercourse which, because it is stra ...
*
Riffle A riffle is a shallow landform in a flowing channel. Colloquially, it is a shallow place in a river where water flows quickly past rocks. However, in geology a riffle has specific characteristics. Topographic, sedimentary and hydraulic indica ...
*
Stream gradient Stream gradient (or stream slope) is the grade (slope), grade (or slope) of a stream measured by the ratio of drop in elevation per unit horizontal distance, usually expressed as metre, meters per kilometre, kilometer or Foot (length), feet per mile ...
*
List of waterfalls by flow rate This list of waterfalls by flow rate includes all waterfalls which are known to have an average flow rate or discharge of at least . The waterfalls in this list are those for which there is verifiable information for, and should not be assumed to ...
*
List of waterfalls by type The following is a list of waterfalls by type. * Plunge: Water descends vertically, losing contact with the bedrock surface.


Notes


External links


USGS: Stream Modeling website
{{DEFAULTSORT:Stream Pool Water streams Hydrology Bodies of water