Source (river or stream)
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The headwaters 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 ...

river
or
stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the No ...

stream
is the farthest place in that river or stream from its
estuary An estuary is a partially enclosed Coast, coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime envir ...

estuary
or downstream
confluence In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ...

confluence
with another river, as measured along the course of the river. It is also known as a river's source.


Definition

The
United States Geological Survey The United States Geological Survey, abbreviated USGS and formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the ...
(USGS) states that a river's "length may be considered to be the distance from the mouth to the most distant headwater source (irrespective of stream name), or from the mouth to the headwaters of the stream commonly known as the source stream". As an example of the second definition above, the USGS at times considers the
Missouri River The Missouri River is the longest 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 ...
as a tributary of the
Mississippi River The Mississippi River is the second-longest river and chief 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 b ...

Mississippi River
. But it also follows the first definition above (along with virtually all other geographic authorities and publications) in using the combined Missouri—lower Mississippi length figure in lists of lengths of rivers around the world. Most rivers have numerous tributaries and change names often; it is customary to regard the longest tributary or stem as the source, regardless of what name that watercourse may carry on local maps and in local usage. This most commonly identified definition of a river source specifically uses the most distant point (along watercourses from the
river mouth A river mouth is where a river flows into a larger body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an offi ...

river mouth
) in the
drainage basin A drainage basin is any area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water. The drainage basin includes all the surface water from surface runoff, rain runoff, snowm ...

drainage basin
from which water runs year-around ( perennially), or, alternatively, as the furthest point from which water could possibly flow ephemerally. The 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 ( ), or simply, the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

Smithsonian Institution
, is also used by the
National Geographic Society The National Geographic Society (NGS), headquartered in Washington, D.C., United States, is one of the largest non-profit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, and ...
when pinpointing the source of rivers such as the
Amazon Amazon usually refers to: * Amazons In Greek mythology, the Amazons (Ancient Greek: Ἀμαζόνες ''Amazónes'', singular Ἀμαζών ''Amazōn'') are portrayed in a number of ancient Greek, ancient epic poems and legends, such as the ...

Amazon
or
Nile The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nub ...
. A definition given by the state of
Montana Montana () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper ...

Montana
agrees, stating that a river source is never a
confluence In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ...
but is "in a location that is the farthest, along water miles, from where that river ends." Under this definition, neither a lake (excepting lakes with no inflows) nor a confluence of tributaries can 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 virtually every other geographic authority and atlas define the source of the Nile River not as
Lake Victoria Lake Victoria ( luo, Nam Lolwe; lg, 'Nnalubaale; rw, Nyanza; also ''Ukerewe'') is one of the African Great Lakes. Though having multiple local language names, the lake was renamed after Queen Victoria by the explorer John Hanning Speke, the ...

Lake Victoria
's outlet where the name "Nile" first appears, which would reduce the Nile's length by over (dropping it to fourth or fifth on the list of world's rivers), but instead use the source of the largest river flowing ''into'' the lake, the
Kagera River The Kagera River, also known as Akagera River, or Alexandra Nile, is an East African river, forming part of the upper headwaters of the Nile and carrying water from its most distant source.Stanley, H.M., 1899, Through the Dark Continent, London: G ...
. Likewise, the source of the Amazon River has been determined this way, even though the river changes names numerous times along its course. However, the source of the
Thames The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England Southern England, or the South of England, also known as the South, is an area of England consisting of its southernm ...
in England is traditionally reckoned according to the named river Thames rather than its longer tributary, the
Churn Churn may refer to: * Churn drill, large-diameter drilling machine large holes appropriate for holes in the ground Dairy-product terms * Butter churn, device for churning butter * Churning (butter), the process of creating butter out of milk or ...
— although not without contention. When not listing river lengths, however, alternative definitions may be used. The Missouri River's source is named by some USGS and other federal and state agency sources, following
Lewis Lewis may refer to: Names * Lewis (given name) Lewis () is a masculine English given name, English-language given name. It was coined as an anglicisation of given names in other languages. "Lewis" has been used to anglicise the Irish language, Ir ...

Lewis
and
Clark Clark is an English language surname, ultimately derived from the Latin language, Latin with historical links to England and Ireland ''clericus'' meaning "scribe", "secretary" or a scholar within a religious order, referring to someone who was educ ...

Clark
's naming convention, as the confluence of the
MadisonMadison may refer to: People * Madison (name), a given name and a surname * James Madison (1751–1836), fourth president of the United States Place names * Madison, Wisconsin, the state capital of Wisconsin and the largest city known by this ...
and
Jefferson River The Jefferson River is a tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem r ...
s, rather than the source of its longest tributary (the Jefferson). This contradicts the most common definition, which is, according to a
US Army Corps of Engineers The United States Army Corps of Engineers (USACE) is an Military engineering, engineer formation of the United States Army that has three primary mission areas: engineer regiment, military construction, and civil works. The day-to-day activi ...
official on a USGS site, that " eographersgenerally follow the longest tributary to identify the source of rivers and streams." In the case of the Missouri River, this would have the source be well upstream from Lewis and Clark's confluence, "following the Jefferson River to the
Beaverhead River The Beaverhead River is an approximately tributary of the Jefferson River The Jefferson River is a tributary A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributar ...
to Red Rock River, then Red Rock Creek to
Hell Roaring Creek Hell Roaring Creek is a fast-running creek in southern Montana Montana () is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * T ...
."


Characteristics

Sometimes the source of the most remote tributary may be in an area that is more
marsh A marsh is a wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes prevail ...

marsh
-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 River Tees (), in Northern England Northern England, also known as the North of England or simply the North, is the most northern area of England England is a that is part of the . It shares land borders with to its west and ...
is
marsh A marsh is a wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes prevail ...

marsh
land. The furthest stream is also often called the head stream. Headwaters are often small streams with 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 glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the ...

glacial
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

ice
. Headwater areas are the upstream areas of a
watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins ** European watershed * Drainage basin, ...

watershed
, as opposed to the outflow or discharge of a watershed. The river source is often but not always on or quite near the edge of the watershed, or watershed divide. For example, the source of the
Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

Colorado River
is at the
Continental Divide A continental divide is a drainage divide on a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven regions are commonly regarded as co ...

Continental Divide
separating the and
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. ...

Pacific Ocean
watersheds of
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
.


Example

A ''river'' is considered a ''linear'' geographic feature, with only one mouth and one source. For an example, note how the
Mississippi River The Mississippi River is the second-longest river and chief 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 b ...

Mississippi River
and
Missouri River The Missouri River is the longest 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 ...
sources are officially defined: * *, Length: , Source: *, Length: , Source:


Related usages

The verb "rise" can be used to express the general region of a river's source, and is often qualified with an adverbial expression of place. For example: *''The River Thames rises in Gloucestershire.'' *''The White Nile rises in the Great Lakes region of central Africa.'' The word "source", when applied to
lake A lake is an area filled with water, localized in a basin, surrounded by land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable ove ...

lake
s rather than rivers or streams, refers to the lake's inflow.


See also

*
Source of the Amazon River The main source of the largest river in the world has been a subject of exploring and speculations for centuries and continues to cause arguments even today. Determining the origin of the Amazon River has evoked broad debates among scholars, explo ...
*
Source of the Nile The Nile ( ar, النيل, an-Nīl, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū) is a major north-flowing river in northeastern Africa. The longest river in Africa, it has historically been considered the List of rivers by l ...
*
Spring (hydrology) A spring is a point at which water flows from an aquifer An aquifer is an underground layer of -bearing , rock fractures or unconsolidated materials (, , or ). can be extracted using a water . The study of water flow in aquifers and the ch ...
*
Strahler number In mathematics Mathematics (from Ancient Greek, Greek: ) includes the study of such topics as quantity (number theory), mathematical structure, structure (algebra), space (geometry), and calculus, change (mathematical analysis, analysis). It ...
*
Water well A well is an excavation or structure created in the ground by digging Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surf ...

Water well


References

DeBarry, Paul A. (2004). Watersheds: Processes, Assessment and Management. John Wiley & Sons. {{Rivers, streams and springs Water streams Fluvial landforms Freshwater ecology River morphology