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A river is a natural flowing
watercourse 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 ...
, usually
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which ...
, flowing towards an
ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distribution on Earth, Earth's water. An ocean can also refer to any of the ...
,
sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Water distributio ...
,
lake A lake is an area filled with water, localized in a Depression (geology), basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the World Ocean, oce ...
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 water. Small rivers can be referred to using names such as creek, brook, rivulet, and
rill In Geomorphology#Hillslope processes, hillslope geomorphology, a rill is a shallow Channel (geography), channel (no more than a few inches/decimeters deep) cut into soil by the erosion, erosive action of overland flow, flowing surface water. Si ...
. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a
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 ...
is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "
burn A burn is an injury to skin, or other tissues, caused by heat, cold, electricity, chemicals, friction, or ultraviolet radiation (like sunburn). Most burns are due to heat from hot liquids (called scalding), solids, or fire. Burns occur mainl ...
" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague. Rivers are part of the
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly const ...
. Water generally collects in a river from
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, Rain and snow mixed, sleet, snow, ice pellets, ...
through a
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter ...
from
surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the s ...
and other sources such as
groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical ...
, springs, and the release of stored water in natural ice and
snowpack Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as th ...
s. Rivers are often considered major features within a landscape; however, they actually only cover around 0.1% of the land on Earth. They are made more obvious and significant to humans since many human cities and civilizations are built around the freshwater supplied by rivers and streams. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for
transport Transport (in British English), or transportation (in American English), is the intentional Motion, movement of humans, animals, and cargo, goods from one location to another. Mode of transport, Modes of transport include aviation, air, land ...
, as
border Borders are usually defined as geographical boundaries, imposed either by features such as ocean The ocean (also the sea or the world ocean) is the body of Saline water, salt water that covers approximately 70.8% of the surface of Earth ...
s, as a defensive measure, as a source of
hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, converting the Pot ...
to drive machinery, for
bathing Bathing is the act of washing the body, usually with water, or the immersion of the body in water. It may be practiced for personal hygiene, religious ritual or therapy, therapeutic purposes. By analogy, especially as a recreational activity, the ...
, and as a means of disposing of
waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor Value (economics), economic v ...
. In the pre-industrial era, larger rivers were a major obstruction to the movement of people, goods, and armies across them. Towns often developed at the few locations they could be crossed. Many major cities such as
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
are located at the lowest point at which a river could be bridged. Potamology is the scientific study of rivers, while
limnology Limnology ( ; from Greek λίμνη, ''limne'', "lake" and λόγος, ''logos'', "knowledge") is the study of inland aquatic ecosystems. The study of limnology includes aspects of the biology, biological, chemistry, chemical, physics, physical, ...
is the study of inland waters in general.


Topography


Source and drainage basin

A river begins at a
source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute o ...
(or more often several sources) which is usually a watershed, drains all the streams in its
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter ...
, follows a watercourse, and ends either at a
mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on t ...
or mouths which could be a
confluence In geography, a confluence (also: ''conflux'') occurs where two or more flowing bodies of water join to form a single channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main stem); o ...
,
river delta A river delta is a landform shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, res ...
, etc. The water in a river is usually confined to a channel, made up of a
stream bed A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow (Channel (geography), channel). The lateral confines or channel margins are known as the stream Bank (geography), banks ...
between banks. In larger rivers there is often also a wider
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
shaped by
flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study o ...
-waters over-topping the channel. Floodplains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred, especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry. The term upriver (or upstream) refers to the direction towards the source of the river, i.e. against the direction of flow. Likewise, the term downriver (or downstream) describes the direction towards the mouth of the river, in which the
current Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...
flows. The term left bank refers to the left bank in the direction of flow, right bank to the right in the direction of flow.


Channels

Rivers can flow down mountains, through
valley A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...
s or along
plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or Highland, up ...
s, and can create
canyon A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tenden ...
s or gorges. The river channel typically contains a single stream, but some rivers flow as several interconnecting streams, producing a
braided river A braided river, or braided channel, consists of a network of river channel (geography), channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers ...
. Braided rivers occur on
peneplain file:Peneplain.jpg, 390px, Sketch of a hypothetical peneplain formation after an orogeny. In geomorphology and geology, a peneplain is a Terrain#Low-relief, low-relief plain formed by protracted erosion. This is the definition in the broadest of t ...
s and some of the larger
river delta A river delta is a landform shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, res ...
s. Anastamosing rivers are similar to braided rivers and are quite rare; they have multiple sinuous channel - 1 carrying large volumes of sediment. There are rare cases of
river bifurcation River bifurcation (from la, furca, fork) occurs when a river flowing in a single stream separates into two or more separate streams (called distributary, distributaries) which then continue downstream. Some rivers form complex networks of distri ...
in which a river divides, and the resultant flows end in different seas. An example is the Nerodime River in
Kosovo Kosovo ( sq, Kosova or ; sr-Cyrl, Косово ), officially the Republic of Kosovo ( sq, Republika e Kosovës, links=no; sr, Република Косово, Republika Kosovo, links=no), is a international recognition of Kosovo, partiall ...
. A river flowing in its channel is a source of energy that acts on the river channel to change its shape and form. In 1757, German hydrologist Albert Brahms empirically observed that the submerged weight of objects that may be carried away by a river is proportional to the sixth power of the river flow speed. This formulation is also sometimes called Airy's law. Thus, if the speed of flow is doubled, the flow would dislodge objects with 64 times as much submerged weight. In mountainous torrential zones, this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. A river valley that was created from a U-shaped
glaciated A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
valley can often easily be identified by the V-shaped channel that it has carved. In the middle reaches where a river flows over flatter land,
meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank) and deposits sedimen ...
s may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an
oxbow lake An oxbow lake is a U-shaped lake or stream pool, pool that forms when a wide meander of a river is meander cutoff, cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called ''resaca (channel), re ...
or
billabong Billabong ( ) is an Australia, Australian term for an oxbow lake, an isolated pond left behind after a river changes course. Billabongs are usually formed when the path of a stream, creek or river changes, leaving the former branch with a dead ...
. Rivers that carry large amounts of
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...
may develop conspicuous deltas at their mouths. Rivers whose mouths are in saline tidal waters may form
estuaries An estuary is a partially enclosed 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 environment ...
. Throughout the course of the river, the total volume of water transported downstream will often be a combination of the free water flow together with a substantial volume flowing through sub-surface rocks and gravels that underlie the river and its floodplain (called the
hyporheic zone The hyporheic zone is the region of sediment and porous space beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water. The flow dynamics and behavior in this zone (termed hyporheic flow or underflow) is re ...
). For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.


Types and ratings

Rivers have been classified by many criteria including their
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scien ...
, their biotic status, and their relevance to white water
rafting Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a ...
or
canoe A canoe is a lightweight narrow watercraft, water vessel, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel and using a single-bladed paddle. In British Englis ...
ing activities.


Subsurface rivers: subterranean and subglacial

Most but not all rivers flow on the surface.
Subterranean river A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth. It is distinct from an aquifer, which may flow like a river but is contained within a Per ...
s flow underground in
cave A cave or cavern is a natural void in the Earth#Surface, ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller opening ...
s. Such rivers are frequently found in regions with
limestone Limestone (calcium carbonate ) is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime_(material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphis ...
geologic formations.
Subglacial stream Subglacial streams are conduits of glacial meltwater that flow at the base of glaciers and ice caps.
Hooke, Roger LeB. ...
s are the braided rivers that flow at the beds of glaciers and
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica Antarctica () is Earth's southernmost and ...
s, permitting meltwater to be discharged at the front of the glacier. Because of the gradient in
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
from the overlying weight of the glacier, such streams can even flow uphill.


Permanence of flow: perennial and ephemeral

An
intermittent river Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years.(Tzoraki et al., 2007) Such rivers drain large arid and semi-arid areas, covering approximately a third of the earth's surface. ...
(or
ephemeral Ephemerality (from the Greek language, Greek word , meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and ...
river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur because of geologic conditions such as a highly permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter. Such rivers are typically fed from
chalk Chalk is a soft, white, permeability (Earth sciences), porous, sedimentary rock, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic pl ...
aquifers which recharge from winter rainfall. In England these rivers are called ''bournes'' and give their name to places such as
Bournemouth Bournemouth () is a coastal resort town in the Bournemouth, Christchurch and Poole council area of Dorset, England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders with ...
and
Eastbourne Eastbourne () is a town and seaside resort in East Sussex, on the south coast of England, east of Brighton Brighton () is a seaside resort and one of the two main areas of the City of Brighton and Hove in the county of East Sussex, Eng ...
. Even in humid regions, the location where flow begins in the smallest
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 river drain the surrounding drainage b ...
streams generally moves upstream in response to precipitation and downstream in its absence or when active summer vegetation diverts water for evapotranspiration. Normally dry rivers in arid zones are often identified as arroyos or other regional names. The meltwater from large hailstorms can create a
slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
of water, hail and sand or soil, forming temporary rivers.


Stream order classification

The Strahler Stream Order ranks rivers based on the connectivity and hierarchy of contributing tributaries. Headwaters are first order while the
Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the List of rivers by discharge, largest river by Discharge (hydrology), discharge volume of water in the world, and the disputed List of river systems by length, ...
is twelfth order. Approximately 80% of the rivers in the world are of the first and second order. The ways in which a river's characteristics vary between its upper and lower course are summarized by the Bradshaw model. Power-law relationships between channel slope, depth, and width are given as a function of discharge by "
river regime The river regime generally describes the character of the typical fluctuations of flow of a river, but can also refer to the mathematical relationship between the river discharge and its width, depth and slope. Thus, "river regime" can describe one ...
". In certain languages, distinctions are made among rivers based on their stream order. In French, for example, rivers that run to the sea are called ''fleuve'', while other rivers are called ''rivière''. For example, in Canada, the Churchill River in
Manitoba Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
is called ''la rivière Churchill'' as it runs to
Hudson Bay Hudson Bay ( crj, text=ᐐᓂᐯᒄ, translit=Wînipekw; crl, text=ᐐᓂᐹᒄ, translit=Wînipâkw; iu, text=ᑲᖏᖅᓱᐊᓗᒃ ᐃᓗᐊ, translit=Kangiqsualuk ilua or iu, text=ᑕᓯᐅᔭᕐᔪᐊᖅ, translit=Tasiujarjuaq; french: b ...
, but the Churchill River in
Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Provinces and territories of C ...
is called ''le fleuve Churchill'' as it runs to the Atlantic Ocean. As most rivers in France are known by their names only without the word ''rivière'' or ''fleuve'' (e.g. ''la
Seine The Seine ( , ) is a river in northern France. Its drainage basin is in the Paris Basin (a geological relative lowland) covering most of northern France. It rises at Source-Seine, northwest of Dijon in northeastern France in the Langres plateau, ...
'', not ''le fleuve Seine'', even though the Seine is classed as a ''fleuve''), one of the most prominent rivers in the Francophone commonly known as ''fleuve'' is ''le fleuve Saint-Laurent'' (the St. Lawrence River). Since many ''fleuves'' are large and prominent, receiving many tributaries, the word is sometimes used to refer to certain large rivers that flow into other ''fleuves''; however, even small streams that run to the sea are called ''fleuve'' (e.g. '' fleuve côtier'', "coastal ''fleuve''").


Topographical classification

Rivers can generally be classified as either
alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
,
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 ...
, or some mix of the two. Alluvial rivers have channels and floodplains that are self-formed in unconsolidated or weakly consolidated sediments. They
erode Erode () is a city in the Indian state of Tamil Nadu. Erode is the seventh largest urban agglomeration in the state, after Chennai, Coimbatore, Madurai, Tiruchirapalli, Tiruppur and Salem, Tamil Nadu, Salem. It is also the administrative headq ...
their banks and deposit material on bars and their floodplains. Bedrock rivers form when the river downcuts through the modern sediments and into the underlying bedrock. This occurs in regions that have experienced some kind of uplift (thereby steepening river gradients) or in which a particularly hard
lithology The lithology of a Rock (geology), rock unit is a description of its physical characteristics visible at outcrop, in hand or core sample, core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain ...
causes a river to have a steepened reach that has not been covered in modern
alluvium Alluvium (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around ...
. Bedrock rivers very often contain alluvium on their beds; this material is important in eroding and sculpting the channel. Rivers that go through patches of bedrock and patches of deep alluvial cover are classified as mixed bedrock-alluvial. Alluvial rivers can be further classified by their channel pattern as meandering, braided, wandering, anastomose, or straight. The morphology of an alluvial river reach is controlled by a combination of sediment supply, substrate composition, discharge, vegetation, and bed
aggradation Aggradation (or alluviation) is the term used in geology for the increase in land elevation, typically in a river system, due to the deposition (geology), deposition of sediment. Aggradation occurs in areas in which the supply of sediment is grea ...
.


Biotic classification

There are several systems of classification based on ecological conditions typically assigning classes from the most
oligotroph An oligotroph is an organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into ...
ic or unpolluted through to the most
eutrophic Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly Nitrogen cycle, nitrogen and Phosphorus cycle, phosphorus. It has also been defined as "nutri ...
or polluted. Other systems are based on a whole eco-system approach such as developed by the New Zealand Ministry for the Environment. In Europe, the requirements of the
Water Framework Directive The Water Framework Directive 2000/60/EC is an EU directive which commits European Union member states to achieve good qualitative and quantitative status of all Body of water, water bodies (including marine ecosystem, marine waters up to one na ...
has led to the development of a wide range of classification methods including classifications based on fishery status A system of river zonation used in francophone communities divides rivers into three primary zones: * The ''crenon'' is the uppermost zone at the source of the river. It is further divided into the eucrenon (spring or boil zone) and the hypocrenon (brook or headstream zone). These areas have low temperatures, reduced oxygen content and slow moving water. * The ''rhithron'' is the upstream portion of the river that follows the crenon. It has relatively cool temperatures, high oxygen levels, and fast, turbulent, swift flow. * The ''potamon'' is the remaining downstream stretch of river. It has warmer temperatures, lower oxygen levels, slow flow and sandier bottoms.


Navigability

The international scale of river difficulty is used to rate the challenges of navigation—particularly those with
rapids Rapids are sections of a river where the river bed has a relatively steep stream gradient, gradient, causing an increase in water velocity and turbulence. Rapids are hydrology, hydrological features between a ''run'' (a smoothly flowing part of ...
. Class I is the easiest and Class VI is the hardest.


Streamflow

Studying the flows of rivers is one aspect of
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 ...
.


Characteristics


Direction

Rivers flow downhill with their power derived from gravity. A
common misconception Each entry on this list of common misconceptions is worded as a correction; the misconceptions themselves are implied rather than stated. These entries are concise summaries of the main subject articles, which can be consulted for more detail. ...
holds that all or most rivers flow from north to south, but this is not so: rivers flow in all directions of the compass and often have complex meandering paths. Rivers flowing downhill, from river source to river mouth, do not necessarily take the shortest path. For alluvial streams, straight and braided rivers have very low sinuosity and flow directly down hill, while meandering rivers flow from side to side across a valley. Bedrock rivers typically flow in either a
fractal In mathematics, a fractal is a geometric shape containing detailed structure at arbitrarily small scales, usually having a fractal dimension strictly exceeding the topological dimension. Many fractals appear similar at various scales, as illus ...
pattern, or a pattern that is determined by weaknesses in the bedrock, such as faults, fractures, or more erodible layers.


Rate

Volumetric flow rate In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes ). I ...
, also known as discharge, volume flow rate, and rate of water flow, is the volume of water which passes through a given cross-section of the river channel per unit time. It is typically measured in cubic metres per second (cumec) or cubic feet per second (cfs). Volumetric flow rate can be thought of as the mean velocity of the flow through a given cross-section, times that cross-sectional area. Mean velocity can be approximated through the use of the law of the wall. In general, velocity increases with the depth (or hydraulic radius) and slope of the river channel, while the cross-sectional area scales with the depth and the width: the double-counting of depth shows the importance of this variable in determining the discharge through the channel.


Effects


Fluvial erosion

In its youthful stage, a river causes erosion in the watercourse, deepening the valley.
Hydraulic action Hydraulic action, most generally, is the ability of moving water (flowing or waves) to dislodge and transport rock particles. This includes a number of specific erosional processes, including abrasion, at facilitated erosion, such as ''static eros ...
loosens and dislodges aggregate which further erodes the banks and the river bed. Over time, this deepens the river bed and creates steeper sides which are then weathered. The steepened nature of the banks causes the sides of the valley to move downslope causing the valley to become V-shaped.
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 also form in the youthful river valley where a band of hard rock overlays a layer of soft rock. Differential erosion occurs as the river erodes the soft rock more readily than the hard rock, this leaves the hard rock more elevated and stands out from the river below. A
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 ...
forms at the bottom and deepens as a result of hydraulic action and abrasion.


Flooding

Flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study o ...
ing is a natural part of a river's cycle. The majority of the erosion of river channels and the erosion and deposition on the associated floodplains occur during the flood stage. In many developed areas, human activity has changed the form of river channels, altering magnitudes and frequencies of flooding. Some examples of this are the building of levees, the straightening of channels, and the draining of natural wetlands. In many cases human activities in rivers and floodplains have dramatically increased the risk of flooding. Straightening rivers allows water to flow more rapidly downstream, increasing the risk of flooding places further downstream. Building on flood plains removes flood storage, which again exacerbates downstream flooding. The building of levees only protects the area behind the levees and not those further downstream. Levees and flood-banks can also increase flooding upstream because of the back-water pressure as the river flow is impeded by the narrow channel banks. Detention basins finally also reduce the risk of flooding significantly by being able to take up some of the flood water.


Sediment yield

Sediment yield is the total quantity of particulate matter (suspended or bedload) reaching the outlet of a drainage basin over a fixed time frame. Yield is usually expressed as kilograms per square kilometre per year. Sediment delivery processes are affected by a myriad of factors such as drainage area size, basin slope, climate, sediment type (lithology), vegetation cover, and human land use / management practices. The theoretical concept of the 'sediment delivery ratio' (ratio between yield and total amount of sediment eroded) indicates that not all of the sediment is eroded within a certain catchment that reaches out to the outlet (e.g., deposition on floodplains). Such storage opportunities are typically increased in catchments of larger size, thus leading to a lower yield and sediment delivery ratio.


Brackish water

Brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary ...
occurs in most rivers where they meet the sea. The extent of brackish water may extend a significant distance upstream, especially in areas with high tidal ranges.


Ecosystem


River biota

The organisms in the
riparian zone A riparian zone or riparian area is the interface between land and 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 gro ...
respond to changes in river channel location and patterns of flow. The ecosystem of rivers is generally described by the river continuum concept, which has some additions and refinements to allow for dams and waterfalls and temporary extensive flooding. The concept describes the river as a system in which the physical parameters, the availability of food particles and the composition of the ecosystem are continuously changing along its length. The food (energy) that remains from the upstream part is used downstream. The general pattern is that the first order streams contain particulate matter (decaying leaves from the surrounding forests) which is processed there by shredders like
Plecoptera Plecoptera is an order (biology), order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to ...
larvae. The products of these shredders are used by collectors, such as Hydropsychidae, and further downstream algae that create the
primary production In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
become the main food source of the organisms. All changes are gradual and the distribution of each species can be described as a
normal curve In statistics, a normal distribution or Gaussian distribution is a type of continuous probability distribution for a real number, real-valued random variable. The general form of its probability density function is : f(x) = \frac e^ The param ...
, with the highest density where the conditions are optimal. In rivers succession is virtually absent and the composition of the ecosystem stays fixed.


Chemistry

The chemistry of rivers is complex and depends on inputs from the atmosphere, the geology through which it travels and the inputs from man's activities. The chemical composition of the water has a large impact on the ecology of that water for both plants and animals and it also affects the uses that may be made of the river water. Understanding and characterizing river water chemistry requires a well designed and managed sampling and analysis.


Uses


Construction material

The coarse sediments,
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
sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...
, generated and moved by rivers are extensively used in construction. In parts of the world this can generate extensive new lake habitats as
gravel pit A gravel pit is an open-pit mine for the extraction of 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 l ...
s fill with water. In other circumstances it can destabilize the river bed, and the course of the river and cause severe damage to
spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic ani ...
fish populations which rely on stable gravel formations for egg laying. In upland rivers, rapids with
whitewater Whitewater forms in a rapid context, in particular, when a river's Stream gradient, gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that foam, froths, making the wat ...
or even waterfalls occur. Rapids are often used for recreation, such as
whitewater kayaking Whitewater kayaking is an adventure sport where a river is navigated in a decked kayak A kayak is a small, narrow watercraft which is typically propelled by means of a double-bladed paddle. The word kayak originates from the Greenlandic wor ...
.


Energy production

Fast flowing rivers and waterfalls are widely used as sources of energy, via
watermill A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as mill (grinding), milling (grinding), rolling, or hammering. Such processes are needed in ...
s and hydroelectric plants. Evidence of watermills shows them in use for many hundreds of years, for instance in
Orkney Orkney (; sco, Orkney; on, Orkneyjar; nrn, Orknøjar), also known as the Orkney Islands, is an archipelago in the Northern Isles of Scotland, situated off the north coast of the island of Great Britain. Orkney is 10 miles (16 km) north ...
at Dounby Click Mill. Prior to the invention of
steam power A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a Cylinder (locomotive), cylinder. This pus ...
, watermills for grinding cereals and for processing wool and other textiles were common across Europe. In the 1890s the first machines to generate power from river water were established at places such as
Cragside Cragside is a Victorian era, Victorian country house near the town of Rothbury in Northumberland, England. It was the home of William Armstrong, 1st Baron Armstrong, founder of the Armstrong Whitworth armaments firm. An industrial magnate, scien ...
in
Northumberland Northumberland () is a ceremonial counties of England, county in Northern England, one of two counties in England which border with Scotland. Notable landmarks in the county include Alnwick Castle, Bamburgh Castle, Hadrian's Wall and Hexham Ab ...
and in recent decades there has been a significant increase in the development of large scale power generation from water, especially in wet mountainous regions such as Norway.


Food source

Rivers have been a source of food since pre-history. They are often a rich source of fish and other edible aquatic life and are a major source of fresh water, which can be used for drinking and irrigation. Rivers help to determine the urban form of cities and neighborhoods, and their corridors often present opportunities for
urban renewal Urban renewal (also called urban regeneration in the United Kingdom and urban redevelopment in the United States) is a program of land redevelopment often used to address urban decay in cities. Urban renewal involves the clearing out of blighte ...
through the development of foreshoreways such as river walks. Rivers also provide an easy means of disposing of
wastewater Wastewater is water generated after the use of Fresh water, freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domesti ...
and, in much of the less developed world, other wastes.


Navigation and transport

Rivers have been used for
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navi ...
for thousands of years. The earliest evidence of navigation is found in the
Indus Valley civilization The Indus Valley Civilisation (IVC), also known as the Indus Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 Common Era, BCE to 1300 BCE, and in its mature form 2600 B ...
, which existed in northwestern India around 3300 BC. Riverine navigation provides a cheap means of transport and is still used extensively on most major rivers of the world like the
Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technology co ...
, the
Ganges The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...
, the
Nile The Nile, , Bohairic , lg, Kiira , Nobiin language, Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered ...
, the
Mississippi Mississippi () is a U.S. state, state in the Southeastern United States, Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; a ...
, and the
Indus The Indus ( ) is a transboundary river of Asia and a trans-Himalayan river of South Asia, South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in Western Tibet, flows northwest through the disputed region ...
. In some heavily forested regions such as
Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
and Canada,
lumberjack Lumberjacks are mostly North American workers in the logging industry who perform the initial harvesting and transport of trees for ultimate processing into forest products. The term usually refers to loggers in the era (before 1945 in the Unite ...
s use rivers to float felled trees downstream to lumber camps for further processing, saving much effort and cost by transporting the huge heavy logs by natural means.


Political borders

Rivers have been important in determining political boundaries and defending countries. For example, the
Danube The Danube ( ; ) is a river that was once a long-standing frontier of the Roman Empire and today connects 10 European countries, running through their territories or being a border. Originating in Germany, the Danube flows southeast for , pa ...
was a long-standing border of the
Roman Empire The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Roman Republic, Republican period of ancient Rome. As a polity, it included large territorial holdings aro ...
, and today it forms most of the border between
Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria,, ) is a country in Southeast Europe. It is situated on the eastern flank of the Balkans, and is bordered by Romania to the north, Serbia and North Macedon ...
and
Romania Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...
. The Mississippi in North America and the
Rhine The Rhine ; french: Rhin ; nl, Rijn ; wa, Rén ; li, Rien; rm, label=Sursilvan, Rein, rm, label=Sutsilvan and Surmiran, Ragn, rm, label=Rumantsch Grischun, Vallader and Puter, Rain; it, Reno ; gsw, Rhi(n), including in Alsatian dialect, Al ...
in Europe are major east–west boundaries in those continents. The
Orange Orange most often refers to: *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Orange (colour), from the color of an orange, occurs between red and yellow in the visible spectrum * ...
and
Limpopo Limpopo is the northernmost Provinces of South Africa, province of South Africa. It is named after the Limpopo River, which forms the province's western and northern borders. The capital and largest city in the province is Polokwane, while th ...
Rivers in
southern Africa Southern Africa is the southernmost subregion of the African continent, south of Congo Basin, the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to ...
form the boundaries between provinces and countries along their routes.


Sacred rivers

Sacred rivers and their reverence is a phenomenon found in several religions, especially religions in which nature is revered. For example, the Indian-origin religions of
Buddhism Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religions, Indian religion or Indian philosophy#Buddhist philosophy, philosophical tradition based on Pre-sectarian Buddhism, teachings attributed to the Buddha. ...
,
Hinduism Hinduism () is an Indian religions, Indian religion or ''dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the Major religious groups, world's third-largest, with over 1.2–1.35 billion ...
,
Jainism Jainism ( ), also known as Jain Dharma, is an Indian religions, Indian religion. Jainism traces its spiritual ideas and history through the succession of twenty-four tirthankaras (supreme preachers of ''Dharma''), with the first in the current ...
, and
Sikhism Sikhism (), also known as Sikhi ( pa, ਸਿੱਖੀ ', , from pa, ਸਿੱਖ, lit=disciple', 'seeker', or 'learner, translit=Sikh, label=none),''Sikhism'' (commonly known as ''Sikhī'') originated from the word ''Sikh'', which comes fro ...
revere and preserve groves,
forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may ...
s,
trees In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondar ...
,
mountains A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited Summit (topography), summit area, and ...
and rivers as sacred. Among the most sacred rivers in Hinduism are the
Ganges The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...
,
Yamuna The Yamuna (Hindustani language, Hindustani: ), also spelt Jumna, is the second-largest tributary river of the Ganges by discharge and the longest tributary in List of major rivers of India, India. Originating from the Yamunotri Glacier at a ...
, and
Sarasvati Saraswati ( sa, सरस्वती, ) is the Hindu Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used a ...
rivers. Other sacred rivers for Indian religions include the
Rigvedic rivers 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 bod ...
, the Narmada, the
Godavari The Godavari (International Alphabet of Sanskrit Transliteration, IAST: ''Godāvarī'' Help:IPA/Sanskrit, od̪aːʋəɾiː is India's second longest river after the Ganges river, Ganga river and drains into the third largest basin in Indi ...
, and the
Kaveri The Kaveri (also known as Cauvery, the anglicized name) is one of the major Indian rivers flowing through the states of Karnataka and Tamil Nadu. The Kaveri river rises at Talakaveri in the Brahmagiri (hill), Karnataka, Brahmagiri range in th ...
rivers. The
Vedas FIle:Atharva-Veda samhita page 471 illustration.png, upright=1.2, The Vedas are ancient Sanskrit texts of Hinduism. Above: A page from the ''Atharvaveda''. The Vedas (, , ) are a large body of religious texts originating in ancient India. Co ...
and
Gita The Bhagavad Gita (; sa, श्रीमद्भगवद्गीता, lit=The Song by God, translit=śrīmadbhagavadgītā;), often referred to as the Gita (), is a 700-Sanskrit prosody, verse Hindu texts, Hindu scripture that is part o ...
, the most sacred of
Hindu texts Hindu texts are manuscripts and voluminous historical literature which are related to any of the diverse traditions within Hinduism. A few of these texts are shared across these traditions and they are broadly considered Hindu scriptures. These ...
, were written on the banks of the Sarasvati river.


Management

Rivers are often managed or controlled to make them more useful or less disruptive to human activity. * Dams or weirs may be built to control the flow, store water, or extract energy. * Levees, known as dikes in Europe, may be built to prevent river water from flowing on floodplains or floodways. * Canals connect rivers to one another for water transfer or navigation. * River courses may be modified to improve navigation, or straightened to increase the flow rate. River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life. Rivers are increasingly managed for
habitat conservation Habitat conservation is a management practice that seeks to Conservation (ethic), conserve, protect and restore habitats and prevent species extinction, habitat fragmentation, fragmentation or reduction in Range (biology), range. It is a priori ...
, as they are critical for many aquatic and riparian plants,
resident Resident may refer to: People and functions * Resident minister A resident minister, or resident for short, is a Official, government official required to take up permanent residence in another country. A representative of his government, ...
and migratory fishes, waterfowl,
birds of prey Birds of prey or predatory birds, also known as raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and other smaller birds). In addition to speed and strength, these p ...
, migrating birds, and many mammals.


Concerns

Man-made causes, such as the
over-exploitation Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Continued overexploitation can lead to the destruction of the resource, as it will be unable to replenish. The term app ...
and pollution, are the biggest threats and concerns which are making rivers ecologically dead and drying up the rivers.
Plastic pollution Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...
imposes threats on aquatic life and river ecosystems because of
plastic Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...
's durability in the natural environment. Plastic debris may result in entanglement and ingestion by aquatic life such as turtles, birds, and fish, causing severe injury and death. Human livelihoods around rivers are also impacted by plastic pollution through direct damage to shipping and transport vessels, effects on tourism or real estate value, and the clogging of drains and other hydraulic infrastructure leading to increased flood risk.


See also

;Arts, entertainment, and media * " Old Man River" * '' The Riverkeepers'' (book) ;General *
Drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D.  Jiang, A.  Khan, W.  Pokam Mba, D.  Rosenfeld, J. Tierney, an ...
*
Fluvial In geography and geology, fluvial processes are associated with rivers and streams and the Deposition (geology), deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glac ...
*
Reach (geography) A reach is a segment of a stream, river, or arm (geography), arm of the sea, usually suggesting a straight, level, uninterrupted stretch. They are traditionally defined by the Point of sail#Reaching, capabilities of sailing boats, as a stretch of ...
*
Salt tide Salt tide is a phenomenon in which the lower course 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 d ...
*
Water conflict Water conflict is a term describing a conflict between countries, states, or groups over the rights to access water resources. The United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to ...
;Crossings *
Bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...
*
Ferry A ferry is a ship, watercraft or amphibious vehicle used to carry passengers, and sometimes vehicles and cargo, across a body of water. A passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water taxi ...
*
Ford (crossing) A ford is a shallow place with good footing where a river or stream may be crossed by wading, or inside a vehicle getting its wheels wet. A ford may occur naturally or be constructed. Fords may be impassable during high water. A low-water cr ...
*
Tunnel A tunnel is an underground passageway, dug through surrounding soil, earth or rock, and enclosed except for the entrance and exit, commonly at each end. A Pipeline transport, pipeline is not a tunnel, though some recent tunnels have used ...
;Habitats * Exposed riverine sediments *
Riparian zone A riparian zone or riparian area is the interface between land and 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 gro ...
;Lists *
Lists of rivers This is a comprehensive list of lists of 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 ...
*
List of international border rivers This is a List of international river borders. Rivers that form any portion of the border between two countries minimum: By region Africa image:African continent-en.svg, 300px, Countries in Africa The following rivers form borders of countri ...
* List of rivers by continent * List of rivers by discharge *
List of rivers by length This is a list of the longest rivers on Earth. It includes river systems over in length. Definition of length There are many factors, such as the identification of the source, the identification or the definition of the mouth, and the scale of ...
* List of waterways ;Transport *
Barge Barge nowadays generally refers to a flat-bottomed boat, flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by Pusher (boat) ...
*
Raft A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a Hull (watercraft), hull. Rafts are usually kept afloat by using any combination of buoyant materials such as w ...
* River transport *
Riverboat A riverboat is a watercraft designed for inland navigation on lakes, rivers, and artificial waterways. They are generally equipped and outfitted as work boats in one of the carrying trades, for freight or people transport, including luxury un ...
*
Sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, Windsurfing, windsurfer, or Kitesurfing, kitesurfer), on ''ice'' (iceboat) or on ''land'' (Land s ...
*
Steamboat A steamboat is a boat that is marine propulsion, propelled primarily by marine steam engine, steam power, typically driving propellers or Paddle steamer, paddlewheels. Steamboats sometimes use the ship prefix, prefix designation SS, S.S. or S/S ...
*
Towpath A towpath is a road or trail on the bank of a river, canal, or other inland waterway. The purpose of a towpath is to allow a land vehicle, Working animal, beasts of burden, or a team of human pullers to tow a boat, often a barge. This mod ...
*
Yacht A yacht is a sailing or power vessel used for pleasure, cruising, or racing. There is no standard definition, though the term generally applies to vessels with a cabin intended for overnight use. To be termed a , as opposed to a , such a pleasu ...


References


Further reading

* * — a non-technical primer on the
geomorphology Geomorphology (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following ...
and
hydraulics Hydraulics (from Greek language, Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is th ...
of water. * {{Authority control Bodies of water Fluvial landforms Geomorphology Sedimentology Water streams