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A river is a natural
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 strea ...
of
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...
that flows on
land Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% of Earth's surface and includes all continents and islands. Earth's land sur ...
or inside
caves Caves or caverns are natural voids under the Earth's surface. Caves often form by the weathering of rock and often extend deep underground. Exogene caves are smaller openings that extend a relatively short distance underground (such as rock ...
towards another
body of water A body of water or waterbody is any significant accumulation of water on the surface of Earth or another planet. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ponds, wetlands, or more rare ...
at a lower
elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...
, such as an
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
,
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
, or another river. A river may run dry before reaching the end of its course if it runs out of water, or only flow during certain seasons. Rivers are regulated by the
water cycle The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...
, the processes by which
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
moves around the
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
.
Water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
first enters rivers through
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
, whether from rainfall, the runoff of water down a slope, the melting of
glaciers A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
or
snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...
, or seepage from
aquifers An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...
beneath the surface of the Earth. Rivers flow in channeled
watercourses 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 strea ...
and merge in
confluence In geography, a confluence (also ''conflux'') occurs where two or more watercourses join to form a single channel (geography), channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main ...
s to form
drainage basins A drainage basin is an area of land in which 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, th ...
, or catchments, areas where surface water eventually flows to a common outlet. Rivers have a great effect on the
landscape A landscape is the visible features of an area of land, its landforms, and how they integrate with natural or human-made features, often considered in terms of their aesthetic appeal.''New Oxford American Dictionary''. A landscape includes th ...
around them. They may regularly overflow their
banks A bank is a financial institution that accepts deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital markets. As banks ...
and
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 of significant con ...
the surrounding area, spreading
nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
s to the surrounding area. Sediment or
alluvium Alluvium (, ) 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. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
carried by rivers shapes the landscape around it, forming
deltas A river delta is a landform, wikt:archetype#Noun, archetypically triangular, created by the deposition (geology), deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or ...
and
island An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been ...
s where the flow slows down. Rivers rarely run in a straight line, instead, they bend or
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, cut bank or river cl ...
; the locations of a river's banks can change frequently. Rivers get their
alluvium Alluvium (, ) 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. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
from
erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
, which carves rock into
canyons A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
and
valleys A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a ve ...
. Rivers have sustained
human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...
and
animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
life for millennia, including the first human
civilization A civilization (also spelled civilisation in British English) is any complex society characterized by the development of state (polity), the state, social stratification, urban area, urbanization, and symbolic systems of communication beyon ...
s. The organisms that live around or in a river such as
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
,
aquatic plants Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...
,
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
,
molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...
, and
insects Insects (from Latin ') are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed ...
have different roles, including
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 ...
, processing
organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...
,
predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
,
parasitism Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...
, and
decomposition Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ess ...
. Rivers have produced abundant resources for humans, including
food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...
,
transportation 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 tr ...
,
drinking water Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...
, and
recreation Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for happiness, enjoyment, amusement, ...
. Humans have throughout
history History is the systematic study of the past, focusing primarily on the Human history, human past. As an academic discipline, it analyses and interprets evidence to construct narratives about what happened and explain why it happened. Some t ...
engineered rivers to prevent flooding,
irrigate Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has be ...
crops, perform work with
water wheels A water wheel is a machine for converting the kinetic energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wheel (usually constructed from wood or metal), with numerous blade ...
, and produce
hydroelectricity Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
from dams. Since ancient times, people have associated rivers with
life Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...
and
fertility Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate ...
and have attached strong
religious Religion is a range of social- cultural systems, including designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relate humanity to supernatural ...
,
political Politics () is the set of activities that are associated with decision-making, making decisions in social group, groups, or other forms of power (social and political), power relations among individuals, such as the distribution of Social sta ...
,
social Social organisms, including human(s), live collectively in interacting populations. This interaction is considered social whether they are aware of it or not, and whether the exchange is voluntary or not. Etymology The word "social" derives fro ...
, and
myth Myth is a genre of folklore consisting primarily of narratives that play a fundamental role in a society. For scholars, this is very different from the vernacular usage of the term "myth" that refers to a belief that is not true. Instead, the ...
ological elements to them. To this day, more than 90% of the human population lives within 10 miles of a river. Rivers and river ecosystems are threatened by
water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...
,
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
, and human activity. The construction of dams,
canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...
s,
levees A levee ( or ), dike (American English), dyke (British English; see spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against fl ...
, and other engineered structures has eliminated habitats, has caused the
extinction Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
of some species, increased
nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
avilability to
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
levels, and lowered the amount of
alluvium Alluvium (, ) 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. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
flowing through rivers. Decreased
snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...
fall from climate change has resulted in less water available for rivers during the
summer Summer or summertime is the hottest and brightest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, daylight hours are the longest and darkness hours are the shortest, with day ...
. Regulation of
pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
,
dam removal Dam removal is the process of demolishing a dam, returning water flow to the river. Arguments for dam removal consider whether their negative effects outweigh their benefits. The benefits of dams include hydropower production, flood control, ir ...
, and
sewage treatment Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water p ...
have helped to improve
water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
and restore river habitats. Certain organisms such as
sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s and
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
are useful bioindicators for river health.


Topography


Definition

A river is a natural flow of
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
that flows on or through
land Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% of Earth's surface and includes all continents and islands. Earth's land sur ...
towards another body of water downhill. This flow can be into a
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
, an
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
, or another river. 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 strea ...
refers to water that flows in a natural
channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Australia in Queensland and pa ...
, a geographic feature that can contain flowing water. A stream may also be referred to as a watercourse. The study of the movement of water as it occurs on Earth is called
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 drainage basin sustainability. A practitioner of hydrology is called a hydro ...
, and their effect on the landscape is covered by
geomorphology Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...
.


Source and drainage basin

Rivers are part of the
water cycle The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...
, the continuous processes by which
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
moves about Earth. This means that all water that flows in rivers must ultimately come from
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
. The sides of rivers have land that is at a higher
elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...
than the river itself, and in these areas, water flows downhill into the river. The
headwaters The headwater of a river or stream is the geographical point of its beginning, specifically where surface runoff water begins to accumulate into a flowing channel of water. A river or stream into which one or many tributary rivers or streams flo ...
of a river are the smaller
streams A stream is a continuous body of surface water flowing within the bed and banks of a channel. Depending on its location or certain characteristics, a stream may be referred to by a variety of local or regional names. Long, large stream ...
that feed a river, and make up the river's source. These streams may be small and flow rapidly down the sides of
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 area, and is usually higher ...
. All of the
land Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% of Earth's surface and includes all continents and islands. Earth's land sur ...
uphill of a river that feeds it with water in this way is in that river's
drainage basin A drainage basin is an area of land in which 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, ...
or watershed. A
ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...
of higher elevation land is what typically separates drainage basins; water on one side of a ridge will flow into one set of rivers, and water on the other side will flow into another. One example of this is the
Continental Divide of the Americas The Continental Divide of the Americas (also known as the Great Divide, the Western Divide or simply the Continental Divide; ) is the principal, and largely mountainous, hydrological divide of the Americas. The Continental Divide extends from t ...
in the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
. Water on the western side of the divide flows into the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
, whereas water on the other side flows into the
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
. Not all precipitation flows directly into rivers; some water seeps into underground
aquifers An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...
. These, in turn, can still feed rivers via the
water table The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...
, the
groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...
beneath the surface of the land stored in the
soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
. Water flows into rivers in places where the river's elevation is lower than that of the water table. This phenomenon is why rivers can still flow even during times of
drought A drought is a period of 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, ...
. Rivers are also fed by the melting of
snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...
glaciers A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
present in higher elevation regions. In
summer Summer or summertime is the hottest and brightest of the four temperate seasons, occurring after spring and before autumn. At or centred on the summer solstice, daylight hours are the longest and darkness hours are the shortest, with day ...
months, higher temperatures melt snow and ice, causing additional water to flow into rivers. Glacier melt can supplement snow melt in times like the late summer, when there may be less snow left to melt, helping to ensure that the rivers downstream of the glaciers have a continuous supply of water.


The flow of rivers

Rivers flow downhill, with their direction determined by
gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
. 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; the main subject articles can be consulted for more detail. Common mis ...
holds that all or most rivers flow from North to South, but this is not true. As rivers flow downstream, they eventually merge to form larger rivers. A river that feeds into another is a
tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''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 into which they ...
, and the place they meet is a
confluence In geography, a confluence (also ''conflux'') occurs where two or more watercourses join to form a single channel (geography), channel. A confluence can occur in several configurations: at the point where a tributary joins a larger river (main ...
. Rivers must flow to lower altitudes due to
gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
. The
bed A bed is a piece of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many beds ...
of a river is typically within a
river valley A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a ...
between
hills A hill is a landform that extends above the surrounding terrain. It often has a distinct summit, and is usually applied to peaks which are above elevation compared to the relative landmass, though not as prominent as mountains. Hills fall und ...
or
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 area, and is usually higher ...
. Rivers flowing through an impermeable section of land such as rocks will
erode Erode (; īrōṭu), is a city in the Indian state of Tamil Nadu. It is located on the banks of the Kaveri river and is surrounded by the Western Ghats. Erode is the seventh largest urban agglomeration in Tamil Nadu. It is the administrativ ...
the slopes on the sides of the river. When a river carves a
plateau In geology and physical geography, a plateau (; ; : plateaus or plateaux), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. ...
or a similar high-elevation area, a
canyon A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
can form, with cliffs on either side of the river. Areas of a river with softer rock
weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmo ...
faster than areas with harder rock, causing a difference in elevation between two points of a river. This can cause the formation of a
waterfall A waterfall is any 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 seve ...
as the river's flow falls down a vertical drop. A river in a permeable area does not exhibit this behavior and may even have raised
banks A bank is a financial institution that accepts deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital markets. As banks ...
due to sediment. Rivers also change their landscape through their transportation of
sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
, often known as
alluvium Alluvium (, ) 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. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
when applied specifically to rivers. This debris comes from erosion performed by the rivers themselves, debris swept into rivers by rainfall, as well as erosion caused by the slow movement of glaciers. The sand in deserts and the sediment that forms bar islands is from rivers. The
particle size Particle size is a notion introduced for comparing dimensions of solid particles ('' flecks''), liquid particles ('' droplets''), or gaseous particles ('' bubbles''). The notion of particle size applies to particles in colloids, in ecology, in ...
of the debris is gradually sorted by the river, with heavier particles like
rocks In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's ...
sinking to the bottom, and finer particles like
sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...
or
silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...
carried further
downriver Downriver is a region of the Detroit metropolitan area in the U.S. state of Michigan covering 18 municipalities in Wayne County, south of Detroit, along the western shore of the Detroit River. Etymology The name derives from the fact that the ...
. This sediment may be deposited in river valleys or carried to the
sea A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...
. The sediment yield of a river is the quantity of sand per unit area within a watershed that is removed over a period of time. The monitoring of the sediment yield of a river is important for ecologists to understand the health of its ecosystems, the rate of erosion of the river's environment, and the effects of human activity. Rivers rarely run in a straight direction, instead preferring to bend or
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, cut bank or river cl ...
. This is because any natural impediment to the flow of the river may cause the current to deflect in a different direction. When this happens, the alluvium carried by the river can build up against this impediment, redirecting the course of the river. The flow is then directed against the opposite bank of the river, which will erode into a more concave shape to accommodate the flow. The bank will still block the flow, causing it to reflect in the other direction. Thus, a bend in the river is created. Rivers may run through low, flat regions on their way to the sea. These places may have
floodplains A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge.Goudie, ...
that are periodically flooded when there is a high level of water running through the river. These events may be referred to as "wet seasons' and "dry seasons" when the flooding is predictable due to the
climate Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteoro ...
. The alluvium carried by rivers, laden with minerals, is deposited into the floodplain when the banks spill over, providing new nutrients to the soil, allowing them to support human activity like farming as well as a host of plant and animal life. Deposited sediment from rivers can form temporary or long-lasting fluvial islands. These islands exist in almost every river.


Non-perennial rivers

About half of all waterways on Earth are intermittent rivers, which do not always have a continuous flow of water throughout the year. This may be because an arid climate is too dry depending on the season to support a stream, or because a river is seasonally frozen in the winter (such as in an area with substantial
permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...
), or in the headwaters of rivers in mountains, where
snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many part ...
is required to fuel the river. These rivers can appear in a variety of climates, and still provide a habitat for aquatic life and perform other ecological functions.


Subterranean rivers

Subterranean river A subterranean river (also known as an underground river) is a river or watercourse that runs wholly or partly beneath the ground, one where the riverbed does not represent the surface of the Earth. It is distinct from an aquifer, which may flow ...
s may flow underground through flooded caves. This can happen in
karst Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...
systems, where rock dissolves to form caves. These rivers provide a habitat for diverse
microorganisms A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...
and have become an important target of study by
microbiologists A microbiologist (from Greek ) is a scientist who studies microscopic life forms and processes. This includes study of the growth, interactions and characteristics of microscopic organisms such as bacteria, algae, fungi, and some types of paras ...
. Other rivers and streams have been covered over or converted to run in tunnels due to human development. These rivers do not typically host any life, and are often used only for
stormwater Stormwater, also written storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed lan ...
or flood control. One such example is the Sunswick Creek in New York City, which was covered in the 1800s and now exists only as a sewer-like pipe.


The terminus

While rivers may flow into
lakes A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...
or man-made features such as
reservoirs A reservoir (; ) is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of water, interrup ...
, the water they contain will always tend to flow down toward the
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
. However, if human activity siphons too much water away from a river for other uses, the riverbed may run dry before reaching the sea. The outlets
mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...
of a river can take several forms.
Tidal river A tidal river is a river whose flow and level are caused by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it had been given a separate and another title name. Gene ...
s (often part of an
estuary 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 enviro ...
) have their levels rise and fall with the
tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...
. Since the levels of these rivers are often already at or near sea level, the flow of alluvium and the
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 ...
that flows in these rivers may be either
upriver In hydrology, a current in a water body is the flow of water in any one particular direction. The current varies spatially as well as temporally, dependent upon the flow volume of water, stream gradient, and channel geometry. In tidal zones, ...
or downriver depending on the time of day. Rivers that are not tidal may form
deltas A river delta is a landform, wikt:archetype#Noun, archetypically triangular, created by the deposition (geology), deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or ...
that continuously deposit alluvium into the sea from their mouths. Depending on the activity of waves, the strength of the river, and the strength of the tidal current, the sediment can accumulate to form new land. When viewed from above, a delta can appear to take the form of several
triangular A triangle is a polygon with three corners and three sides, one of the basic shapes in geometry. The corners, also called ''vertices'', are zero-dimensional points while the sides connecting them, also called ''edges'', are one-dimensional ...
shapes as the river mouth appears to fan out from the original
coastline A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...
.


Classification

In
hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...
, a stream order is a positive integer used to describe the level of river branching in a drainage basin. Several systems of stream order exist, one of which is the
Strahler number In mathematics, the Strahler number or Horton–Strahler number of a mathematical tree (graph theory), tree is a numerical measure of its branching complexity. These numbers were first developed in hydrology, as a way of measuring the complexity ...
. In this system, the first tributaries of a river are 1st order rivers. When two 1st order rivers merge, the resulting river is 2nd order. If a river of a higher order and a lower order merge, the order is incremented from whichever of the previous rivers had the higher order. Stream order is correlated with and thus can be used to predict certain data points related to rivers, such as the size of the drainage basin (drainage area), and the length of the channel.


Ecology


Models


River Continuum Concept

The ecosystem of a river includes the life that lives in its water, on its banks, and in the surrounding land. The width of the channel of a river, its velocity, and how shaded it is by nearby trees. Creatures in a river ecosystem may be divided into many roles based on the River Continuum Concept. "Shredders" are organisms that consume this organic material. The role of a "grazer" or "scraper" organism is to feed on the
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
that collects on rocks and plants. "Collectors" consume the
detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...
of dead organisms. Lastly,
predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
feed on living things to survive. The river can then be modeled by the availability of resources for each creature's role. A shady area with
deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
trees might experience frequent deposits of
organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...
in the form of leaves. In this type of ecosystem, collectors and shredders will be most active. As the river becomes deeper and wider, it may move slower and receive more
sunlight Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...
. This supports
invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...
and a variety of
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
, as well as scrapers feeding on algae. Further downstream, the river may get most of its energy from organic matter that was already processed upstream by collectors and shredders. Predators may be more active here, including fish that feed on plants,
plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
, and other fish.


Flood pulse concept

The
flood pulse concept The flood pulse concept explains how the periodic inundation and drought (flood pulse) control the lateral exchange of water, nutrients and organisms between the main river channel (or lake) and the connected floodplain. The annual flood pulse is ...
focuses on habitats that flood seasonally, including
lakes A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...
and
marshes In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in general ...
. The land that interfaces with a water body is that body's
riparian zone A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripari ...
. Plants in the riparian zone of a river help stabilize its banks to prevent erosion and filter alluvium deposited by the river on the shore, including processing the
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
and other nutrients it contains. Forests in a riparian zone also provide important animal
habitats In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
.


Fish zonation concept

River ecosystems have also been categorized based on the variety of aquatic life they can sustain, also known as the fish zonation concept. Smaller rivers can only sustain smaller fish that can comfortably fit in its waters, whereas larger rivers can contain both small fish and large fish. This means that larger rivers can host a larger variety of species. This is analogous to the species-area relationship, the concept of larger habitats being host to more species. In this case, it is known as the species-discharge relationship, referring specifically to the discharge of a river, the amount of water passing through it at a particular time.


Movement of organisms

The flow of a river can act as a means of transportation for different organisms, as well as a barrier. For example, the Amazon River is so wide in parts that the variety of species on either side of its basin are distinct. Some
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
may swim upstream to
spawn Spawn or spawning may refer to: * Spawning, the eggs and sperm of aquatic animals Arts, entertainment and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** ''Spawn: Armageddon' ...
as part of a seasonal
migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...
. Species that travel from the
sea A sea is a large body of salt water. There are particular seas and the sea. The sea commonly refers to the ocean, the interconnected body of seawaters that spans most of Earth. Particular seas are either marginal seas, second-order section ...
to breed in
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
rivers are
anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousa ...
, and fish that travel from rivers to the
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
to breed are
catadromous Fish migration is animal migration, mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few ...
.
Salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...
s are anadromous fish that may die in the river after spawning, contributing
nutrients A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
back to the
river ecosystem River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts.Angelier, ...
.
Fungal A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradit ...
spores also sometimes move via stream currents, and some species depend on this to spread between substrates.


Human uses


Infrastructure

Modern river engineering involves a large-scale collection of independent river engineering structures that have the goal of
flood control Flood management or flood control are methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and ru ...
, improved navigation, recreation, and ecosystem management. Many of these projects have the effect of normalizing the effects of rivers; the greatest floods are smaller and more predictable, and larger sections are open for navigation by boats and other watercraft. A major effect of river engineering has been a reduced sediment output of large rivers. For example, the
Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...
produced 400 million tons of sediment per year. Due to the construction of
reservoirs A reservoir (; ) is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of water, interrup ...
, sediment buildup in man-made
levees A levee ( or ), dike (American English), dyke (British English; see spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against fl ...
, and the removal of natural banks replaced with revetments, this sediment output has been reduced by 60%. The most basic river projects involve the clearing of obstructions like fallen trees. This can scale up to
dredging Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing d ...
, the excavation of sediment buildup in a channel, to provide a deeper area for navigation. These activities require regular maintenance as the location of the river banks changes over time, floods bring foreign objects into the river, and natural sediment buildup continues. Artificial
channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Australia in Queensland and pa ...
are often constructed to "cut off" winding sections of a river with a shorter path, or to direct the flow of a river in a straighter direction. This effect, known as channelization, has made the distance required to traverse the
Missouri River The Missouri River is a river in the Central United States, Central and Mountain states, Mountain West regions of the United States. The nation's longest, it rises in the eastern Centennial Mountains of the Bitterroot Range of the Rocky Moun ...
in shorter. Dikes are channels built perpendicular to the flow of the river beneath its surface. These help rivers flow straighter by increasing the speed of the water at the middle of the channel, helping to control floods. Levees are also used for this purpose. They can be thought of as dams constructed on the sides of rivers, meant to hold back water from flooding the surrounding area during periods of high rainfall. They are often constructed by building up the natural terrain with soil or clay. Some levees are supplemented with floodways, channels used to redirect floodwater away from farms and populated areas.
Dams A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, ...
restrict the flow of water through a river. They can be built for navigational purposes, providing a higher level of water upstream for boats to travel in. They may also be used for
hydroelectricity Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...
, or power generation from rivers. Dams typically transform a section of the river behind them into a lake or reservoir. This can provide nearby cities with a predictable supply of drinking water. Hydroelectricity is desirable as a form of
renewable energy Renewable energy (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...
that does not require any inputs beyond the river itself. Dams are very common worldwide, with at least 75,000 higher than in the U.S. Globally, reservoirs created by dams cover . Dam-building reached a peak in the 1970s, when between two or three dams were completed every day, and has since begun to decline. New dam projects are primarily focused in
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
,
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
, and other areas in
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
.


History


Pre-industrial era

The first
civilizations A civilization (also spelled civilisation in British English) is any complex society characterized by the development of the state, social stratification, urbanization, and symbolic systems of communication beyond signed or spoken languag ...
of Earth were born on floodplains between 5,500 and 3,500 years ago. The freshwater, fertile soil, and transportation provided by rivers helped create the conditions for complex societies to emerge. Three such civilizations were the
Sumerians Sumer () is the earliest known civilization, located in the historical region of southern Mesopotamia (now south-central Iraq), emerging during the Chalcolithic and early Bronze Ages between the sixth and fifth millennium BC. Like nearby Elam ...
in the
Tigris–Euphrates river system The Tigris–Euphrates river system is a large river system in West Asia that flows into the Persian Gulf. Its primary rivers are the Tigris and Euphrates, along with smaller tributary, tributaries. From their sources and upper courses in the Ar ...
, the
Ancient Egyptian Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...
civilization in the Nile, and 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  BCE to 1300 BCE, and in its mature form from 2600 BCE ...
on the
Indus River The Indus ( ) is a transboundary river of Asia and a trans-Himalayas, Himalayan river of South Asia, South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in the Western Tibet region of China, flows northw ...
. The
desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...
climates of the surrounding areas made these societies especially reliant on rivers for survival, leading to people clustering in these areas to form the first
cities A city is a human settlement of a substantial size. The term "city" has different meanings around the world and in some places the settlement can be very small. Even where the term is limited to larger settlements, there is no universally agree ...
. It is also thought that these civilizations were the first to organize the irrigation of desert environments for growing food. Growing food at scale allowed people to specialize in other roles, form hierarchies, and organize themselves in new ways, leading to the birth of civilization. In
pre-industrial society Pre-industrial society refers to social attributes and forms of political and cultural organization that were prevalent before the advent of the Industrial Revolution, which occurred from 1750 to 1850. ''Pre-industrial'' refers to a time befor ...
, rivers were a source of transportation and abundant resources. Many civilizations depended on what resources were local to them to survive.
Shipping Freight transport, also referred to as freight forwarding, is the physical process of transporting commodities and merchandise goods and cargo. The term shipping originally referred to transport by sea but in American English, it has been ...
of commodities, especially the floating of
wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
on rivers to transport it, was especially important. Rivers also were an important source of
drinking water Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...
. For civilizations built around rivers, fish were an important part of the diet of humans. Some rivers supported fishing activities, but were ill-suited to farming, such as those in the
Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...
. Other animals that live in or near rivers like
frogs A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough skin texture due to ...
,
mussels Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, whic ...
, and
beavers Beavers (genus ''Castor'') are large, semiaquatic rodents of the Northern Hemisphere. There are two existing species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers are the second-large ...
could provide food and valuable goods such as
fur A fur is a soft, thick growth of hair that covers the skin of almost all mammals. It consists of a combination of oily guard hair on top and thick underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as an ...
. Humans have been building
infrastructure Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and pri ...
to use rivers for thousands of years. The
Sadd el-Kafara Sadd el-Kafara ("Dam of the Infidels") was a masonry embankment dam on Wadi al-Garawi 10 km southeast of Helwan in Cairo, Egypt. The dam was built in the first half of the third millennium BC by the ancient Egyptians for flood control and i ...
dam near
Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
, Egypt, is an ancient dam built on the
Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
4,500 years ago. The
Ancient Roman In modern historiography, ancient Rome is the Roman people, Roman civilisation from the founding of Rome, founding of the Italian city of Rome in the 8th century BC to the Fall of the Western Roman Empire, collapse of the Western Roman Em ...
civilization used aqueducts to transport water to
urban areas An urban area is a human settlement with a high population density and an infrastructure of built environment. Urban areas originate through urbanization, and researchers categorize them as cities, towns, conurbations or suburbs. In urbani ...
.
Spanish Muslims Spain is a Christian majority country, with Islam being a minority religion, practised mostly by immigrants from Muslim majority countries, and their descendants. Islam was a major religion on the Iberian Peninsula, beginning with the Muslim ...
used mills and water wheels beginning in the seventh century. Between 130 and 1492, larger dams were built in Japan, Afghanistan, and India, including 20 dams higher than . Canals began to be cut in Egypt as early as 3000 BC, and the mechanical
shadoof A shadoof or shaduf, well pole, well sweep, sweep,Knight, Edward Henry. ''Knight's American mechanical dictionary''. Vol. 3. New York, Hurd and Houghton: Riverside Press, 1877. 2,468. Print. swape, or simply a lift is a tool that is used to lift w ...
began to be used to raise the elevation of water. Drought years harmed crop yields, and leaders of society were incentivized to ensure regular water and food availability to remain in power. Engineering projects like the shadoof and canals could help prevent these crises. Despite this, there is evidence that floodplain-based civilizations may have been abandoned occasionally at a large scale. This has been attributed to unusually large floods destroying infrastructure; however, there is evidence that permanent changes to climate causing higher
aridity Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...
and lower river flow may have been the determining factor in what river civilizations succeeded or dissolved.
Water wheels A water wheel is a machine for converting the kinetic energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wheel (usually constructed from wood or metal), with numerous blade ...
began to be used at least 2,000 years ago to harness the energy of rivers. Water wheels turn an
axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...
that can supply
rotational energy Rotational energy or angular kinetic energy is kinetic energy due to the rotation of an object and is part of its total kinetic energy. Looking at rotational energy separately around an object's axis of rotation, the following dependence on the ob ...
to move water into
aqueducts Aqueduct may refer to: Structures *Aqueduct (bridge), a bridge to convey water over an obstacle, such as a ravine or valley *Navigable aqueduct, or water bridge, a structure to carry navigable waterway canals over other rivers, valleys, railw ...
, work metal using a
trip hammer Trip may refer to: Arts and entertainment Books Fictional characters * Trip (Pokémon), Trip (''Pokémon''), a ''Pokémon'' character * Trip (Power Rangers), in the American television series ''Time Force Power Rangers'' * Trip, in the 2013 film ...
, and grind grains with a
millstone Millstones or mill stones are stones used in gristmills, used for triturating, crushing or, more specifically, grinding wheat or other grains. They are sometimes referred to as grindstones or grinding stones. Millstones come in pairs: a s ...
. In the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, water mills began to automate many aspects of
manual labor Manual labour (in Commonwealth English, manual labor in American English) or manual work is physical work done by humans, in contrast to labour by machines and working animals. It is most literally work done with the hands (the word ''manual'' ...
, and spread rapidly. By 1300, there were at least 10,000 mills in England alone. A medieval watermill could do the work of 30–60 human workers. Water mills were often used in conjunction with dams to focus and increase the speed of the water. Water wheels continued to be used up to and through the
Industrial Revolution The Industrial Revolution, sometimes divided into the First Industrial Revolution and Second Industrial Revolution, was a transitional period of the global economy toward more widespread, efficient and stable manufacturing processes, succee ...
as a source of power for
textile mill Textile manufacturing or textile engineering is a major industry. It is largely based on the conversion of fibre into yarn, then yarn into fabric. These are then dyed or printed, fabricated into cloth which is then converted into useful good ...
s and other factories, but were eventually supplanted by
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. This pushing force can be transf ...
.


Industrial era

Rivers became more
industrialized Industrialisation ( UK) or industrialization ( US) is the period of social and economic change that transforms a human group from an agrarian society into an industrial society. This involves an extensive reorganisation of an economy for the ...
with the growth of technology and the
human population In world demographics, the world population is the total number of humans currently alive. It was estimated by the United Nations to have exceeded eight billion in mid-November 2022. It took around 300,000 years of human prehistory and histor ...
. As fish and water could be brought from elsewhere, and goods and people could be transported via
railways Rail transport (also known as train transport) is a means of transport using wheeled vehicles running in tracks, which usually consist of two parallel steel rails. Rail transport is one of the two primary means of land transport, next to roa ...
, pre-industrial river uses diminished in favor of more complex uses. This meant that the local ecosystems of rivers needed less protection as humans became less reliant on them for their continued flourishing.
River engineering River engineering is a discipline of civil engineering which studies human intervention in the course, characteristics, or flow of a river with the intention of producing some defined benefit. People have intervened in the natural course and b ...
began to develop projects that enabled industrial
hydropower Hydropower (from Ancient Greek -, "water"), also known as water power or water energy, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, ...
,
canals Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flow u ...
for the more efficient movement of goods, as well as projects for
flood prevention Flood management or flood control are methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and ru ...
. River transportation has historically been significantly cheaper and faster than transportation by land. Rivers helped fuel
urbanization Urbanization (or urbanisation in British English) is the population shift from Rural area, rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. ...
as goods such as grain and fuel could be floated downriver to supply cities with resources. River transportation is also important for the
lumber industry The wood industry or timber industry (sometimes lumber industry – when referring mainly to sawed boards) is the industry concerned with forestry, logging, timber trade, and the production of primary forest products and wood products (e.g. fu ...
, as logs can be shipped via river. Countries with dense forests and networks of rivers like
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
have historically benefited the most from this method of trade. The rise of
highway A highway is any public or private road or other public way on land. It includes not just major roads, but also other public roads and rights of way. In the United States, it is also used as an equivalent term to controlled-access highway, or ...
s and the
automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...
has made this practice less common. One of the first large canals was the
Canal du Midi The Canal du Midi (; ) is a long canal in Southern France (). Originally named the ''Canal Royal en Languedoc'' (Royal Canal in Languedoc) and renamed by French revolutionaries to ''Canal du Midi'' in 1789, the canal is considered one of the g ...
, connecting rivers within France to create a path from the
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
to the
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
. The nineteenth century saw canal-building become more common, with the U.S. building of canals by 1830. Rivers began to be used by
cargo ships A cargo ship or freighter is a merchant ship that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year, handling the bulk of international trade. Cargo ships are usual ...
at a larger scale, and these canals were used in conjunction with river engineering projects like dredging and straightening to ensure the efficient flow of goods. One of the largest such projects is that of the
Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...
, whose drainage basin covers 40% of the
contiguous United States The contiguous United States, also known as the U.S. mainland, officially referred to as the conterminous United States, consists of the 48 adjoining U.S. states and the District of Columbia of the United States in central North America. The te ...
. The river was then used for shipping crops from the
American Midwest The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four List of regions of the United States, census regions defined by the United States Census Bureau. It occupies the northern c ...
and cotton from the
American South The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is census regions United States Census Bureau. It is between the Atlantic Ocean and the ...
to other states as well as the Atlantic Ocean. The role of urban rivers has evolved from when they were a center of trade, food, and transportation to modern times when these uses are less necessary. Rivers remain central to the
cultural identity Cultural identity is a part of a person's identity (social science), identity, or their self-conception and self-perception, and is related to nationality, ethnicity, religion, social class, generation, Locality (settlement), locality, gender, o ...
of cities and nations. Famous examples include the
River Thames The River Thames ( ), known alternatively in parts as the The Isis, River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the Longest rivers of the United Kingdom, s ...
's relationship to
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
, the
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 plat ...
to
Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...
, and the
Hudson River The Hudson River, historically the North River, is a river that flows from north to south largely through eastern New York (state), New York state. It originates in the Adirondack Mountains at Henderson Lake (New York), Henderson Lake in the ...
to
New York City New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
. The restoration of water quality and recreation to urban rivers has been a goal of modern administrations. For example,
swimming Swimming is the self-propulsion of a person through water, such as saltwater or freshwater environments, usually for recreation, sport, exercise, or survival. Swimmers achieve locomotion by coordinating limb and body movements to achieve hydrody ...
was banned in the Seine for over 100 years due to concerns about pollution and the spread of
E. coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly foun ...
, until cleanup efforts to allow its use in the
2024 Summer Olympics The 2024 Summer Olympics (), officially the Games of the XXXIII Olympiad () and branded as Paris 2024, were an international multi-sport event held in France from 26 July to 11 August 2024, with several events started from 24 July. P ...
. Another example is the restoration of the
Isar The Isar () is a river in Austria and in Bavaria, Germany. Its source is in the Karwendel mountain range of the Alps. The Isar river enters Germany near Mittenwald and flows through Krün, Wallgau, Bad Tölz, Munich, and Landshut before reaching ...
in
Munich Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
from being a fully canalized channel with hard embankments to being wider with naturally sloped banks and vegetation. This has improved wildlife habitat in the Isar, and provided more opportunities for recreation in the river.


Politics of rivers

As a
natural barrier A natural barrier is a physical feature that protects or hinders travel through or over. Mountains, swamps, deserts and ice fields are among the clearest examples of natural barriers. Rivers are a more ambiguous example, as they may obstruct l ...
, rivers are often used as a border between
countries A country is a distinct part of the Earth, world, such as a state (polity), state, nation, or other polity, political entity. When referring to a specific polity, the term "country" may refer to a sovereign state, List of states with limited r ...
, cities, and other
territories A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
. For example, the
Lamari River The Lamari River is a river that originates in the Kratke Range in the south central highlands of Eastern Highlands Province of Papua New Guinea. It flows into the Purari River basin. Population Awa speaking indigenous people populate the Lamar ...
in
New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...
separates the
Angu The Angu or Änga people, also called Kukukuku (pronounced "cookah-cookah"), are a small group speaking a number of related languagesEthnologue: Languages of the World, Sixteenth Edition, M. Paul Lewis, editor; and living mainly in the high, mo ...
and the Fore people in New Guinea. The two cultures speak different languages and rarely mix. 23% of international borders are large rivers (defined as those over 30 meters wide). The traditional northern border of the
Roman Empire The Roman Empire ruled the Mediterranean and much of Europe, Western Asia and North Africa. The Roman people, Romans conquered most of this during the Roman Republic, Republic, and it was ruled by emperors following Octavian's assumption of ...
was the
Danube The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...
, a river that today forms the border of
Hungary Hungary is a landlocked country in Central Europe. Spanning much of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia and ...
and
Slovakia Slovakia, officially the Slovak Republic, is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the west, and the Czech Republic to the northwest. Slovakia's m ...
. Since the flow of a river is rarely static, the exact location of a river border may be called into question by countries. The
Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...
between the United States and Mexico is regulated by the
International Boundary and Water Commission The International Boundary and Water Commission (IBWC, , CILA) is an international body created by the United States and Mexico in 1889 to apply the rules for determining the location of their international boundary when meandering rivers trans ...
to manage the right to fresh water from the river, as well as mark the exact location of the border. Up to 60% of fresh water used by countries comes from rivers that cross international borders. This can cause disputes between countries that live upstream and downstream of the river. A country that is downstream of another may object to the upstream country diverting too much water for agricultural uses, pollution, as well as the creation of dams that change the river's flow characteristics. For example, Egypt has an agreement with
Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...
requiring a specific minimum volume of water to pass into the Nile yearly over the
Aswan Dam The Aswan Dam, or Aswan High Dam, is one of the world's largest embankment dams, which was built across the Nile in Aswan, Egypt, between 1960 and 1970. When it was completed, it was the tallest earthen dam in the world, surpassing the Chatuge D ...
, to maintain both countries access to water.


Religion and mythology

The importance of rivers throughout
human history Human history or world history is the record of humankind from prehistory to the present. Early modern human, Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers. They Early expansions of hominin ...
has given them an association with
life Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...
and
fertility Fertility in colloquial terms refers the ability to have offspring. In demographic contexts, fertility refers to the actual production of offspring, rather than the physical capability to reproduce, which is termed fecundity. The fertility rate ...
. They have also become associated with the reverse,
death Death is the end of life; the irreversible cessation of all biological functions that sustain a living organism. Death eventually and inevitably occurs in all organisms. The remains of a former organism normally begin to decompose sh ...
and destruction, especially through
floods 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 of significant con ...
. This power has caused rivers to have a central role in
religion Religion is a range of social system, social-cultural systems, including designated religious behaviour, behaviors and practices, morals, beliefs, worldviews, religious text, texts, sanctified places, prophecies, ethics in religion, ethics, or ...
,
ritual A ritual is a repeated, structured sequence of actions or behaviors that alters the internal or external state of an individual, group, or environment, regardless of conscious understanding, emotional context, or symbolic meaning. Traditionally ...
, and
myth Myth is a genre of folklore consisting primarily of narratives that play a fundamental role in a society. For scholars, this is very different from the vernacular usage of the term "myth" that refers to a belief that is not true. Instead, the ...
ology. In
Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
, the
underworld The underworld, also known as the netherworld or hell, is the supernatural world of the dead in various religious traditions and myths, located below the world of the living. Chthonic is the technical adjective for things of the underworld. ...
is bordered by several rivers. Ancient Greeks believed that the
soul The soul is the purported Mind–body dualism, immaterial aspect or essence of a Outline of life forms, living being. It is typically believed to be Immortality, immortal and to exist apart from the material world. The three main theories that ...
s of those who perished had to be borne across the
River Styx In Greek mythology, Styx (; ; lit. "Shuddering"), also called the River Styx, is a goddess and one of the rivers of the Greek Underworld. Her parents were the Titans Oceanus and Tethys, and she was the wife of the Titan Pallas and the mothe ...
on a boat by
Charon In Greek mythology, Charon or Kharon ( ; ) is a psychopomp, the ferryman of the Greek underworld. He carries the souls of those who have been given funeral rites across the rivers Acheron and Styx, which separate the worlds of the living and ...
in exchange for money. Souls that were judged to be good were admitted to
Elysium Elysium (), otherwise known as the Elysian Fields (, ''Ēlýsion pedíon''), Elysian Plains or Elysian Realm, is a conception of the afterlife that developed over time and was maintained by some Greek religious and philosophical sects and cult ...
and permitted to drink water from the River Lethe to forget their previous life. Rivers also appear in descriptions of
paradise In religion and folklore, paradise is a place of everlasting happiness, delight, and bliss. Paradisiacal notions are often laden with pastoral imagery, and may be cosmogonical, eschatological, or both, often contrasted with the miseries of human ...
in
Abrahamic religions The term Abrahamic religions is used to group together monotheistic religions revering the Biblical figure Abraham, namely Judaism, Christianity, and Islam. The religions share doctrinal, historical, and geographic overlap that contrasts them wit ...
, beginning with the story of
Genesis Genesis may refer to: Religion * Book of Genesis, the first book of the biblical scriptures of both Judaism and Christianity, describing the creation of the Earth and of humankind * Genesis creation narrative, the first several chapters of the Bo ...
. A river beginning in the
Garden of Eden In Abrahamic religions, the Garden of Eden (; ; ) or Garden of God ( and ), also called the Terrestrial Paradise, is the biblical paradise described in Genesis 2–3 and Ezekiel 28 and 31.. The location of Eden is described in the Book of Ge ...
waters the garden and then splits into four rivers that flow to provide water to the world. These rivers include the
Tigris and Euphrates ''Tigris and Euphrates'' () is a tabletop eurogame designed by Reiner Knizia and first published in 1997 by Hans im Glück. Before its publication, it was highly anticipated by German gamers hearing rumors of a "gamer's game" designed by K ...
, and two rivers that are possibly apocryphal but may refer to the
Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
and 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 which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...
. The
Quran The Quran, also Romanization, romanized Qur'an or Koran, is the central religious text of Islam, believed by Muslims to be a Waḥy, revelation directly from God in Islam, God (''Allah, Allāh''). It is organized in 114 chapters (, ) which ...
describes these four rivers as flowing with water, milk, wine, and honey, respectively. The book of Genesis also contains a story of a great flood. Similar myths are present in the
Epic of Gilgamesh The ''Epic of Gilgamesh'' () is an epic poetry, epic from ancient Mesopotamia. The literary history of Gilgamesh begins with five Sumerian language, Sumerian poems about Gilgamesh (formerly read as Sumerian "Bilgames"), king of Uruk, some of ...
,
Sumer Sumer () is the earliest known civilization, located in the historical region of southern Mesopotamia (now south-central Iraq), emerging during the Chalcolithic and Early Bronze Age, early Bronze Ages between the sixth and fifth millennium BC. ...
ian mythology, and in other cultures. In Genesis, the flood's role was to cleanse Earth of the wrongdoing of humanity. The act of water working to cleanse humans in a ritualistic sense has been compared to the Christian ritual of
baptism Baptism (from ) is a Christians, Christian sacrament of initiation almost invariably with the use of water. It may be performed by aspersion, sprinkling or affusion, pouring water on the head, or by immersion baptism, immersing in water eit ...
, famously the
Baptism of Jesus The baptism of Jesus, the ritual purification of Jesus with water by John the Baptist, was a major event described in the three synoptic Gospels of the New Testament ( Matthew, Mark and Luke). It is considered to have taken place at Al-Maghta ...
in the
Jordan River The Jordan River or River Jordan (, ''Nahr al-ʾUrdunn''; , ''Nəhar hayYardēn''), also known as ''Nahr Al-Sharieat'' (), is a endorheic river in the Levant that flows roughly north to south through the Sea of Galilee and drains to the Dead ...
. Floods also appear in
Norse mythology Norse, Nordic, or Scandinavian mythology, is the body of myths belonging to the North Germanic peoples, stemming from Old Norse religion and continuing after the Christianization of Scandinavia as the Nordic folklore of the modern period. The ...
, where the world is said to emerge from a void that eleven rivers flowed into.
Aboriginal Australian Aboriginal Australians are the various indigenous peoples of the Australian mainland and many of its islands, excluding the ethnically distinct people of the Torres Strait Islands. Humans first migrated to Australia 50,000 to 65,000 year ...
religion and
Mesoamerican Mesoamerica is a historical region and cultural area that begins in the southern part of North America and extends to the Pacific coast of Central America, thus comprising the lands of central and southern Mexico, all of Belize, Guatemala, El S ...
mythology also have stories of floods, some of which contain no survivors, unlike the Abrahamic flood. Along with mythological rivers, religions have also cared for specific rivers as sacred rivers. The
Ancient Celtic religion Ancient Celtic religion, commonly known as Celtic paganism, was the religion of the ancient Celtic peoples of Europe. Because there are no extant native records of their beliefs, evidence about their religion is gleaned from archaeology, Greco ...
saw rivers as goddesses. The Nile had many gods attached to it. The tears of the goddess
Isis Isis was a major goddess in ancient Egyptian religion whose worship spread throughout the Greco-Roman world. Isis was first mentioned in the Old Kingdom () as one of the main characters of the Osiris myth, in which she resurrects her sla ...
were said to be the cause of the river's yearly flooding, itself personified by the goddess Hapi. Many African religions regard certain rivers as the originator of life. In
Yoruba religion The Yorùbá religion (Yoruba language, Yoruba: Ìṣẹ̀ṣe), West African Orisa (Òrìṣà), or Isese (Ìṣẹ̀ṣe), comprises the traditional religious and spiritual concepts and practice of the Yoruba people. Its homeland is in pres ...
,
Yemọja Yemọja (also: Yemaja, Yemanjá, Yemoyá, Yemayá; there are many different transliterations in other languages) is the major water spirit from the Yoruba religion. She is the mother of all Orishas. She is also the mother of humanity. She is an ...
rules over the
Ogun River The Ogun River ( Yoruba: Odò Ògùn) is a waterway in Nigeria that discharges into the Lagos Lagoon. Ogun State of Nigeria is named after the river. Course and usage The river rises near the towns of Sepeteri and Shaki in upper Oyo State at ...
in modern-day
Nigeria Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea in the Atlantic Ocean to the south. It covers an area of . With Demographics of Nigeria, ...
and is responsible for creating all children and fish. Some sacred rivers have religious prohibitions attached to them, such as not being allowed to drink from them or ride in a boat along certain stretches. In these religions, such as that of the Altai in
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
, the river is considered a living being that must be afforded respect. Rivers are some of the most sacred places in Hinduism. There is archeological evidence that mass ritual bathing in rivers at least 5,000 years ago in the Indus river valley. While most rivers in India are revered, the Ganges is most sacred. The river has a central role in various Hindu myths, and its water is said to have properties of healing as well as
absolution Absolution is a theological term for the forgiveness imparted by ordained Priest#Christianity, Christian priests and experienced by Penance#Christianity, Christian penitents. It is a universal feature of the historic churches of Christendom, alth ...
from sins. Hindus believe that when the
cremated Cremation is a method of Disposal of human corpses, final disposition of a corpse through Combustion, burning. Cremation may serve as a funeral or post-funeral rite and as an alternative to burial. In some countries, including India, Nepal, and ...
remains of a person is released into the Ganges, their soul is released from the mortal world.


Threats

Freshwater fish Freshwater fish are fish species that spend some or all of their lives in bodies of fresh water such as rivers, lakes, ponds and inland wetlands, where the salinity is less than 1.05%. These environments differ from marine habitats in many wa ...
make up 40% of the world's fish species, but 20% of these species are known to have gone extinct in recent years. Human uses of rivers make these species especially vulnerable. Dams and other engineered changes to rivers can block the migration routes of fish and destroy habitats. Rivers that flow freely from headwaters to the sea have better water quality, and also retain their ability to transport nutrient-rich alluvium and other organic material downstream, keeping the ecosystem healthy. The creation of a lake changes the habitat of that portion of water, and blocks the transportation of sediment, as well as preventing the natural meandering of the river. Dams block the migration of fish such as
salmon Salmon (; : salmon) are any of several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the genera ''Salmo'' and ''Oncorhynchus'' of the family (biology), family Salmonidae, native ...
for which
fish ladder A fish ladder, also known as a fishway, fish pass, fish steps, or fish cannon, is a structure on or around artificial and natural barriers (such as dams, locks and waterfalls) to facilitate diadromous fishes' natural migration as well as mov ...
and other bypass systems have been attempted, but these are not always effective.
Pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
from factories and urban areas can also damage water quality. "
Per- and polyfluoroalkyl substances Per- and polyfluoroalkyl substances (also PFAS, PFASs, and informally referred to as "forever chemicals") are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain; there are 7 milli ...
(PFAS) is a widely used chemical that breaks down at a slow rate. It has been found in the bodies of humans and animals worldwide, as well as in the soil, with potentially negative health effects. Research into how to remove it from the environment, and how harmful exposure is, is ongoing.
Fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...
from farms can lead to a proliferation of algae on the surface of rivers and oceans, which prevents
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
and light from dissolving into water, making it impossible for underwater life to survive in these so-called dead zones. Urban rivers are typically surrounded by impermeable surfaces like stone,
asphalt Asphalt most often refers to: * Bitumen, also known as "liquid asphalt cement" or simply "asphalt", a viscous form of petroleum mainly used as a binder in asphalt concrete * Asphalt concrete, a mixture of bitumen with coarse and fine aggregates, u ...
, and concrete. Cities often have storm drains that direct this water to rivers. This can cause flooding risk as large amounts of water are directed into the rivers. Due to these impermeable surfaces, these rivers often have very little alluvium carried in them, causing more erosion once the river exits the impermeable area. It has historically been common for
sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewerage, sewer system. Sewage consists of wastewater discharged fro ...
to be directed directly to rivers via sewer systems without being treated, along with pollution from industry. This has resulted in a loss of animal and plant life in urban rivers, as well as the spread of
waterborne disease Waterborne diseases are conditions (meaning adverse effects on human health, such as death, disability, illness or disorders) caused by pathogenic micro-organisms that are transmitted by water. These diseases can be spread while bathing, washing ...
s such as
cholera Cholera () is an infection of the small intestine by some Strain (biology), strains of the Bacteria, bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea last ...
. In modern times,
sewage treatment Sewage treatment is a type of wastewater treatment which aims to remove contaminants from sewage to produce an effluent that is suitable to discharge to the surrounding environment or an intended reuse application, thereby preventing water p ...
and controls on pollution from factories have improved the water quality of urban rivers.
Climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
can change the flooding cycles and water supply available to rivers. Floods can be larger and more destructive than expected, causing damage to the surrounding areas. Floods can also wash unhealthy chemicals and sediment into rivers.
Droughts A drought is a period of 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, ...
can be deeper and longer, causing rivers to run dangerously low. This is in part because of a projected loss of
snowpack Snowpack is an accumulation of snow that compresses with time and melts seasonally, often at high elevation or high latitude. Snowpacks are an important water resource that feed streams and rivers as they melt, sometimes leading to flooding. Snow ...
in mountains, meaning that melting snow can't replenish rivers during warm summer months, leading to lower water levels. Lower-level rivers also have warmer temperatures, threatening species like salmon that prefer colder upstream temperatures. Attempts have been made to regulate the exploitation of rivers to preserve their ecological functions. Many
wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...
areas have become protected from development. Water restrictions can prevent the complete draining of rivers. Limits on the construction of dams, as well as
dam removal Dam removal is the process of demolishing a dam, returning water flow to the river. Arguments for dam removal consider whether their negative effects outweigh their benefits. The benefits of dams include hydropower production, flood control, ir ...
, can restore the natural habitats of river species. Regulators can also ensure regular releases of water from dams to keep animal habitats supplied with water. Limits on pollutants like
pesticides Pesticides are substances that are used to pest control, control pest (organism), pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for a ...
can help improve water quality.


Extraterrestrial rivers

Today, the surface of
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
does not have liquid water. All
water on Mars Although very small amounts of liquid water may occur transiently on the surface of Mars, limited to traces of dissolved moisture from the atmosphere and thin films, large quantities of ice are present on and under the surface. Small amounts of ...
is part of
permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...
ice caps, or trace amounts of water vapor in the atmosphere. However, there is evidence that rivers flowed on Mars for at least 100,000 years. The
Hellas Planitia Hellas Planitia is a plain located within the huge, roughly circular impact basin Hellas located in the southern hemisphere of the planet Mars. Hellas is the fourth- or fifth-largest known impact crater in the Solar System. The basin floor ...
is a crater left behind by an impact from an asteroid. It has
sedimentary rock Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
that was formed 3.7 billion years ago, and
lava field A lava field, sometimes called a lava bed, is a large, mostly flat area of lava flows. Such features are generally composed of highly fluid basalt lava, and can extend for tens or hundreds of kilometers across the underlying terrain. Morp ...
s that are 3.3 billion years old. High resolution images of the surface of the plain show evidence of a river network, and even river deltas. These images reveal
channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Australia in Queensland and pa ...
formed in the rock, recognized by geologists who study rivers on Earth as being formed by rivers, as well as "bench and slope" landforms, outcroppings of rock that show evidence of river erosion. Not only do these formations suggest that rivers once existed, but that they flowed for extensive time periods, and were part of a water cycle that involved precipitation. The term ''flumen'', in
planetary geology Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of celestial bodies such as planets and their moons, asteroids, comets, and meteorites. Although the geo- prefix t ...
, refers to channels on
Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
's moon
Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...
that may carry liquid. Titan's rivers flow with liquid
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
and
ethane Ethane ( , ) is a naturally occurring Organic compound, organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is List of purification methods ...
. There are river valleys that exhibit wave erosion, seas, and oceans. Scientists hope to study these systems to see how coasts erode without the influence of human activity, something that isn't possible when studying terrestrial rivers.


Rivers by amount of discharge

File:Amazon River ESA387332.jpg, Amazon River File:Varanasiganga.jpg,
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 which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...
File:Aerial view of the Congo River near Kisangani.jpg,
Congo River The Congo River, formerly also known as the Zaire River, is the second-longest river in Africa, shorter only than the Nile, as well as the third-largest river in the world list of rivers by discharge, by discharge volume, following the Amazon Ri ...
File:Orinoco Bridge.jpg,
Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...
File:Dusk on the Yangtze River.jpg,
Yangtze The Yangtze or Yangzi ( or ) is the longest river in Eurasia and the third-longest in the world. It rises at Jari Hill in the Tanggula Mountains of the Tibetan Plateau and flows including Dam Qu River the longest source of the Yangtze, i ...
File:Rio de la Plata BA 2.JPG,
Río de la Plata The Río de la Plata (; ), also called the River Plate or La Plata River in English, is the estuary formed by the confluence of the Uruguay River and the Paraná River at Punta Gorda, Colonia, Punta Gorda. It empties into the Atlantic Ocean and ...
File:Brahmaputra River Homeward bound.jpg,
Brahmaputra River The Brahmaputra is a trans-boundary river which flows through Southwestern China, Northeastern India, and Bangladesh. It is known as Brahmaputra or Luit in Assamese language, Assamese, Yarlung Tsangpo in Lhasa Tibetan, Tibetan, the Siang/Dihan ...
File:Efmo View from Fire Point.jpg,
Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...
File:Слияние рек Енисей.jpg,
Yenisey The Yenisey or Yenisei ( ; , ) is the list of rivers by length, fifth-longest river system in the world, and the largest to drain into the Arctic Ocean. Rising in Mungaragiyn-gol in Mongolia, it follows a northerly course through Lake Baikal a ...
File:Paraná.jpg,
Paraná River The Paraná River ( ; ; ) is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some ."Parana River". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. ...


See also


General

*
Lists of rivers This is a comprehensive list of rivers, organized primarily by continent and country. General lists * List of drainage basins by area (including rivers, lakes, and endorheic basins) * List of largest unfragmented rivers * List of longest undam ...
*
List of waterfalls This list of notable waterfalls of the world is sorted by continent, then country, then province, state or territory. A waterfall is included if it is at least tall and has an existing Wikipedia article, or it is considered historically sig ...
* Salt tide *
Water conflict Water conflict typically refers to violence or disputes associated with access to, or control of, water resources, or the use of water or water systems as weapons or casualties of conflicts. The term ''water war'' is colloquially used in media ...
* Freshwater environmental quality parameters * Potamology *
Limnology Limnology ( ; ) is the study of inland aquatic ecosystems. It includes aspects of the biological, chemical, physical, and geological characteristics of fresh and saline, natural and man-made bodies of water. This includes the study of lakes, ...
* Morge (tributary of the Rhône)


Crossings

*
Bridge A bridge is a structure built to Span (engineering), span a physical obstacle (such as a body of water, valley, road, or railway) without blocking the path underneath. It is constructed for the purpose of providing passage over the obstacle, whi ...
*
Ferry A ferry is a boat or ship that transports passengers, and occasionally vehicles and cargo, across a body of water. A small passenger ferry with multiple stops, like those in Venice, Italy, is sometimes referred to as a water taxi or water bus ...
* Ford *
Tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...


Transport

*
Barge A barge is typically a flat-bottomed boat, flat-bottomed vessel which does not have its own means of mechanical propulsion. Original use was on inland waterways, while modern use is on both inland and ocean, marine water environments. The firs ...
*
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. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barre ...
* 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 ...
*
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 sa ...
*
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. The term ''steamboat'' is used to refer to small steam-powered vessels worki ...
*
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 sail- or marine propulsion, motor-propelled watercraft made 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 ...


References


External links

* * * * {{Authority control Bodies of water Fluvial landforms Geomorphology Sedimentology Water streams