The source of a river A river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there is no or stream A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by is the place from which the water Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state, water vapor or steam in the river or stream originates.

Contents

Definition

The marker indicating the source of the Po River The Po is a river that flows either 652 km (405 mi) or 682 km (424 mi) – considering the length of the Maira, a right bank tributary – eastward across northern Italy, from a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso (in the Cottian Alps) through a delta, near Crissolo Crissolo is a comune in the Province of Cuneo in the Italian region Piedmont, located about 60 km southwest of Turin and about 45 km northwest of Cuneo, on the border with France. The source of the Po River is located in the nearby, at 2,020 m.

More specifically, a source is defined as the most distant point (from the river mouth) in the drainage basin A drainage basin is an extent or area of land where water from rain and melting snow or ice drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, from which water runs year-around, or, alternatively, the furthest point from which water could possibly flow. [1] This latter definition includes sometimes-dry channels and removes any possible definitions that would have the river source "move around" from month to month depending on precipitation or ground water levels. This definition, from geographer Andrew Johnston of the Smithsonian Institution The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities and magazines. Most of its facilities are located in Washington,, is also used by the National Geographic Society The National Geographic Society , headquartered in Washington, D.C. in the United States, is one of the largest non-profit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, the promotion of environmental and historical conservation, and the study of world culture and history when pinpointing the actual source of rivers such as the Amazon The Amazon River (Portuguese: Rio Amazonas; Spanish: Río Amazonas; pronounced /ˈæməzɒn/ ; /ˈæməzən/ (UK)) of South America is the largest river in the world with a total river flow greater than the next ten largest rivers combined. The Amazon, which has the largest drainage basin in the world, accounts for approximately one-fifth of the or Nile The Nile is a major north-flowing river in Africa, generally regarded as the longest river in the world.

Other authoritative geographic definitions agree, stressing that a river source is never a confluence Confluence, in geography, describes the meeting of two or more bodies of water. It usually refers to the point where a tributary joins a more major river, called the mainstem, when that major river is also the highest order stream in the drainage basin but is "in a location that is the farthest, along water miles, from where that river ends." [2]

Thus, neither a lake (except in rare cases in which it has no inflows) nor a confluence of tributaries can by definition ever be a true river source, though both often provide the starting point for the portion of a river carrying a single name. For example, National Geographic and all other major geographic authorities and atlases define the source of the Nile River The Nile is a major north-flowing river in Africa, generally regarded as the longest river in the world not as Lake Victoria Lake Victoria or Victoria Nyanza is one of the African Great Lakes. The lake was named after the United Kingdom's Queen Victoria, by John Hanning Speke, the first European to see the lake's outlet where the name "Nile" first appears, but as the source of the largest river flowing into the lake, the Kagera River.

The official source of the Mississippi-Missouri The length of a river is very hard to calculate. It depends on the identification of the source, the identification of the mouth, and the scale of measurement of the river length between source and mouth. As a result, the length measurements of many rivers are only approximations. In particular, there has long been disagreement as to whether the is not where either river begins in name, but is defined by the USGS The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology, geography, geology, and hydrology. The USGS is a as the source of the longest tributary, the Jefferson River The Jefferson River is a tributary of the Missouri River, approximately 77 miles long, in the U.S. state of Montana[2] The official source of the Amazon River The Amazon River (Portuguese: Rio Amazonas; Spanish: Río Amazonas; pronounced /ˈæməzɒn/ ; /ˈæməzən/ (UK)) of South America is the largest river in the world with a total river flow greater than the next ten largest rivers combined. The Amazon, which has the largest drainage basin in the world, accounts for approximately one-fifth of the is a similar example.[3]

Characteristics of sources

Often the source, or start of the most remote tributary, may be in an area that is more marsh In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, and other herbaceous plants-like, in which the "uppermost" or most remote section of the marsh would be the true source. For example, the source of the River Tees The Tees is a river in Northern England. It rises on the eastern slope of Cross Fell in the Pennines, and flows eastwards for about 85 miles to reach the North Sea between Hartlepool and Redcar. It drains an area of 708 square miles (1834 square km) and subsumes no important tributaries. Before the reorganization of the historic English counties, is marshland In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, and other herbaceous plants.

The furthest stream is also often called the headstream. Headwaters are usually small streams that are often cool waters, because of shade and recently melted ice or snow. They may also be glacial headwaters, waters formed by the melting of glacial A glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology ice Ice, technically, is one of the 15 known crystalline phases of water. In non-scientific contexts, the term usually means ice Ih, which is known to be the most abundant of these solid phases. It can appear transparent or opaque bluish-white colour, depending on the presence of impurities or air inclusions. The addition of other materials such as.

The source is the farthest point of the river stream from its estuary An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea, mouth, or its confluence Confluence, in geography, describes the meeting of two or more bodies of water. It usually refers to the point where a tributary joins a more major river, called the mainstem, when that major river is also the highest order stream in the drainage basin with another river or stream, regardless of what name that watercourse may carry on local maps and in local usage. Where a river is fed by more than one source, it is customary to regard the longest as its source, with other sources considered tributaries A tributary or affluent is a stream or river which flows into a main stem river. A tributary does not flow directly into a sea, ocean, or lake. Tributaries and the mainstem river serve to drain the surrounding drainage basin of its surface water and groundwater by leading the water out into an ocean or some other large body of water. Often, however, the manner in which streams are named is not consistent with this convention. Many rivers change names numerous times over their length.

Near its source, a river or stream may have a modest flow rate The volumetric flow rate in fluid dynamics and hydrometry, is the volume of fluid which passes through a given surface per unit time (for example cubic meters per second [m3 s-1] in SI units, or cubic feet per second [cu ft/s]). It is usually represented by the symbol Q, but the flow increases as more surface runoff Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, snowmelt, or other sources flows over the land. This is a major component of the hydrologic cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source. If a nonpoint source contains man-made and tributaries drain into the subject stream.

Headwaters are the most extreme upstream areas of a watershed. The end point of the watershed A drainage basin is an extent or area of land where water from rain and melting snow or ice drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, is called an outflow or discharge. A watershed is an area of land that is drained by a body of water. The river source is generally on or quite near the edge of the watershed, or watershed divide.

Example

A river is defined as a linear geographic feature, with only one mouth and only one source. For an example, please note how the Mississippi River The Mississippi River is the largest river system in North America. About 2,320 miles long, the river originates at Lake Itasca, Minnesota and flows slowly southwards in sweeping meanders, terminating 95 river miles below New Orleans, Louisiana where it begins to flow to the Gulf of Mexico. Along with its major tributary, the Missouri River, the and Missouri River The Missouri River is the longest river in the United States of America and is a tributary of the Mississippi River. The Missouri likely originates at Brower's Spring at the upper reaches of the Jefferson River, before joining the confluence of the Madison, Jefferson, and Gallatin rivers in Montana. From this point, it flows through its valley sources are officially defined:

Related usages

The verb "rise" can be used to express the idea of a river's source, and is often qualified with an adverbial expression of place. For example:

The word "source", when applied to lakes A lake is a terrain feature , a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is not global). Another definition is a body of fresh or salt water of considerable size that is surrounded by land. On Earth a body of water is considered a lake when it is inland, rather than rivers or streams, refers to the lake's inflow.[4][5]

See also

References

  1. ^ National Geographic News @ nationalgeographic.com
  2. ^ a b The True Utmost Reaches of the Missouri
  3. ^ IBGE - Instituto Brasileiro de Geografia e Estatística
  4. ^ "Owens Valley Particulate Matter Plan: Q & A". Environmental Protection Agency The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged to protect human health and the environment, by writing and enforcing regulations based on laws passed by Congress. The EPA was proposed by President Richard Nixon and began operation on December 2, 1970, when its establishment was passed. http://www.epa.gov/region09/air/owens/qa.html. Retrieved on 2008-05-30. "...the Owens River, the source of the lake..."
  5. ^ Jorge Enrique Casallas Guzmán (2004-02-11). "Limnological investigations in Lake San Pablo" (PDF). http://edocs.tu-berlin.de/diss/2004/casallas_jorge.pdf. Retrieved on 2008-05-30. "...source of the lake is the River Itambi..."

Categories: Water streams | Fluvial landforms | Rivers

 

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