A river is a natural watercourse A watercourse is any flowing body of water. These include rivers, streams, brooks, anabranches, and so forth,[1] usually freshwater Freshwater or fresh water is naturally occurring water on the Earth's surface in bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and, flowing toward an ocean An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (~3.61 X 1014 m2) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas, a lake A lake is a terrain feature , a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is not global). Another definition is a body of fresh or salt water of considerable size that is surrounded by land. On Earth a body of water is considered a lake when it is inland,, a sea A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, the term refers to a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean. It is also used sometimes to describe a large saline lake that lacks a natural outlet, such as the Caspian Sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including stream A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by, creek, brook A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by, rivulet, and rill; there is no general rule that defines what can be called a river. An exception to this is the stream. In some countries or communities a stream A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, crick, kill, lick, rill, river syke, bayou, rivulet, streamage, wash, run or runnel. In some countries or communities a stream may be defined by may be defined by its size. Many names for small rivers are specific to geographic location; one example is Burn in Scotland and North-east England. Sometimes a river is said to be larger than a creek,[2] but this is not always the case, because of vagueness in the language.[3]

A river is part of the hydrological cycle The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Since the water cycle is truly a "cycle," there is no beginning[citation needed] or end. Water can change states among liquid, vapor, and ice at various places in the water cycle. Water within a river is generally collected from precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface. The main forms of precipitation include rain, snow, ice pellets, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water through surface runoff Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, snowmelt, or other sources flows over the land. This is a major component of the hydrologic cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source. If a nonpoint source contains man-made, groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface. Recharge occurs both naturally and anthropologically (i.e., "artificial, springs A spring is a component of the hydrosphere, namely any natural occurrence where water flows to the surface of the earth from below the surface. Thus it is where the aquifer surface meets the ground surface, and the release of stored water in natural ice and snowpacks (e.g., from glaciers A glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology).

Contents

Topography

The water in a river is usually confined to a channel , made up of a stream bed A stream bed is the channel bottom of a stream, river or creek; the physical confine of the normal water flow. The lateral confines or channel margins, during all but flood stage, are known as the stream banks or river banks. In fact, a flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is between banks. In larger rivers there is also a wider floodplain shaped by flood A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flooding may result from the volume of water within a body of water,-waters over-topping the channel. Flood plains may be very wide in relation to the size of the river channel. This distinction between river channel and floodplain can be blurred especially in urban areas where the floodplain of a river channel can become greatly developed by housing and industry.

The term upriver refers to the direction leading to the source of the river, which is against the direction of flow. Likewise, the term downriver describes the direction towards the mouth of the river, in which the current flows.

The river channel typically contains a single stream of water, but some rivers flow as several interconnecting streams of water, producing a braided river Not to be confused with the River Braid, Ballymena, Northern Ireland. For other uses see Braid. Extensive braided rivers are now found in only a few regions worldwide, such as the South Island The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean. The territory of the South Island covers 151,215 square kilometres (58,384 sq mi) and is influenced by a of New Zealand New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori language name for New Zealand is Aotearoa, commonly translated as The Land of the Long White Cloud. The Realm of New Zealand also. They also occur on peneplains A peneplain is a low-relief plain representing the final stage of fluvial erosion during times of extended tectonic stability. The existence of peneplains, and peneplanation as a geomorphological process, is not without controversy, due to a lack of contemporary examples and uncertainty in identifying relic examples and some of the larger river deltas. Anastamosing rivers are similar to braided rivers and are also quite rare. They have multiple sinuous channels carrying large volumes of sediment.

A river flowing in its channel is a source of energy which acts on the river channel to change its shape and form. According to Brahm's law (sometimes called Airy's law), the mass of objects that may be flown away by a river is proportional to the sixth power of the river flow speed. Thus, when the speed of flow increases two times, it can transport 64 times larger (i.e., more massive) objects.[4] In mountainous torrential zones this can be seen as erosion channels through hard rocks and the creation of sands and gravels from the destruction of larger rocks. In U-shaped glaciated A glacier is a perennial mass of ice which moves over land. A glacier forms in locations where the mass accumulation of snow and ice exceeds ablation over many years. The word glacier comes from French via the Vulgar Latin glacia, and ultimately from Latin glacies meaning ice. The corresponding area of study is called glaciology valleys, the subsequent river valley can often easily be identified by the V-shaped channel that it has carved. In the middle reaches where the river may flow over flatter land, meanders A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a river erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternatively eroding sediments from the outside of a bend and depositing them on the inside. The result is a snaking pattern as the may form through erosion of the river banks and deposition on the inside of bends. Sometimes the river will cut off a loop, shortening the channel and forming an oxbow lake An oxbow lake is a U-shaped body of water formed when a wide meander from the main stem of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive curved shape that results from this process. In Australia, an oxbow lake is called a billabong. By itself, the word oxbow can also mean a U-shaped bend in a river or billabong Billabong is an Australian English word meaning a small lake, specifically an oxbow lake, a section of still water adjacent to a river, cut off by a change in the watercourse. Billabongs are usually formed when the path of a creek or river changes, leaving the former branch with a dead end. Despite some claims of a Scottish Gaelic origin, the word. Rivers that carry large amounts of sediment Sediment is naturally-occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself may develop conspicuous deltas A delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Over long periods of time, this deposition builds the at their mouths, if conditions permit. Rivers whose mouths are in saline tidal Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The tides occur with a period of approximately 12 hours and 25 minutes, and with an amplitude that is influenced by the alignment of the sun and moon and the shape of the near-shore waters may form estuaries An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Throughout the course of the river, the total volume of water transported downstream will often be a combination of the free water flow together with a substantial contribution flowing through sub-surface rocks and gravels that underlie the river and its floodplain (called the hyporheic zone The hyporheic zone is a region beneath and lateral to a stream bed, where there is mixing of shallow groundwater and surface water. The flow dynamics and behavior in this zone is recognized to be important for surface water/groundwater interactions, as well as fish spawning, among other processes). For many rivers in large valleys, this unseen component of flow may greatly exceed the visible flow.

Zones

Some researchers[who?] believe that the wide variety of both abiotic and biotic factors involved in rivers defies classification. Nevertheless, one system of river zonation[5][6] has gained relatively widespread acceptance, in the francophone The adjective francophone means French-speaking, typically as primary language, whether referring to individuals, groups, or places. Often, the word is used as a noun to describe a natively French-speaking person world at least. It divides rivers into three primary zones:

Classification

Although the following classes are a useful way to visualize rivers, many other factors are at work. Gradient In vector calculus, the gradient of a scalar field is a vector field which points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change is controlled largely by tectonics, but discharge is controlled largely by climate, and sediment load is controlled by various factors including climate, geology in the headwaters, and the stream gradient.

Youthful river
a river with a steep gradient that has very few tributaries and flows quickly. Its channels erode deeper rather than wider. (Examples: Brazos River The Brazos River, called the Rio de los Brazos de Dios by early Spanish explorers . The Brazos is the longest river in Texas and the 11th longest river in the United States at 2060 km (1280 miles) from its source at the head of Blackwater Draw, Curry County, New Mexico to its mouth at the Gulf of Mexico with a 116,000 km² (44,800 sq mi) drainage, Trinity River The Trinity River is the longest tributary of the Klamath River, approximately 130 miles long, in northwestern California in the United States. It drains an area of the Coast Ranges, including the southern Klamath Mountains, northwest of the Sacramento Valley. Considered especially scenic, along most of its course it flows swiftly through tight, Ebro River The Ebro or Ebre (Catalan, pronounced [ˈeβɾə] or [eβɾe]) is Spain's most voluminous river. Its source is in Fontibre (Cantabria). It flows through cities such as Miranda de Ebro (Castile and Leon), Logroño (La Rioja), Zaragoza (Aragon), and the Catalan cities of Flix, Tortosa, and Amposta before discharging in a delta on the Mediterranean)
Mature river
a river with a gradient that is less steep than those of youthful rivers and flows more slowly. A mature river is fed by many tributaries and has more discharge than a youthful river. Its channels erode wider rather than deeper. (Examples: Mississippi River The Mississippi River is the largest river system in North America. About 2,320 miles long, the river originates at Lake Itasca, Minnesota and flows slowly southwards in sweeping meanders, terminating 95 river miles below New Orleans, Louisiana where it begins to flow to the Gulf of Mexico. Along with its major tributary, the Missouri River, the, St. Lawrence River The Saint Lawrence River is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage of the Great Lakes Basin. It traverses the Canadian provinces of Quebec and Ontario and forms part of the international boundary between, Danube River The Danube is the longest river in the European Union and Europe's second longest river after the Volga, Ohio River The Ohio River is the largest tributary, by volume, of the Mississippi River. It is approximately 1,310 miles long and is located in the Eastern United States, River Thames The River Thames (pronounced /ˈtɛmz/ temz) is a major river flowing through southern England. While it is best known because its lower reaches flow through central London, the river flows through several other towns and cities, including Oxford, Reading and Windsor, Parana river The Paraná River is a river in south central South America, running through Brazil, Paraguay and Argentina over a course of some 2,570 kilometers (1,600 miles). This length increases to 3,998 km (2,484 miles) if the distance is counted from the headwaters of the Paranaiba River in Brazil. It is considered second in size only to the Amazon River)
Old river
a river with a low gradient and low erosive energy. Old rivers are characterized by flood plains. (Examples: Huang He River, Ganges River The Ganges (English pronunciation: /ˈɡændʒiːz/ GAN-jeez; Hindi: गंगा Ganga IPA: [ˈɡəŋɡaː] ; Bengali: গঙ্গা Gônga), is the largest river of the Indian subcontinent, flowing east through the Gangetic Plain of northern India into Bangladesh. The 2,510 km (1,560 mi) river rises in the western Himalayas in the Uttarakhand, Tigris The Tigris River is the eastern member of the two great rivers that define Mesopotamia, along with the Euphrates. The river flows from the mountains of southeastern Turkey through Iraq, Euphrates River The Euphrates ( juːˈfreɪtiːz ) is the longest and historically one of the most important rivers of Southwest Asia. Together with the Tigris, the Euphrates is one of the two defining rivers of Mesopotamia. The river – originating in the Taurus Mountains – flows through Syria and Iraq to join the Tigris in the Shatt al-Arab, which flows into, Indus River The Indus River is a major river which flows through Pakistan, Nile River The Nile is a major north-flowing river in Africa, generally regarded as the longest river in the world)
Rejuvenated river
a river with a gradient that is raised by tectonic Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth (or other planets) and particularly with the forces and movements that have operated in a region to create these structures uplift.

The way in which a river's characteristics vary between the upper course and lower course of a river is summarized by the Bradshaw model The Bradshaw Model is a geographical model which describes how a river's characteristics vary between the upper course and lower course of a river. It shows that discharge, occupied channel width, channel depth and average load quantity increases downstream. Load particle size, channel bed roughness and gradient are all characteristics which.

Most rivers flow on the surface; however subterranean rivers flow underground in caves A cave or cavern is a natural underground space large enough for a human to enter. Some people[who?] suggest that the term cave should only apply to cavities that have some part that does not receive daylight; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and grottos or caverns. Such rivers are frequently found in regions with limestone Limestone is a sedimentary rock composed largely of the mineral calcite . Like most other sedimentary rocks, limestones are composed of grains; however, most grains in limestone grains are skeletal fragments of marine organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts, and geologic formations A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties. Formations are not defined on the thickness of the rock strata they consist of and the thickness of different formations can therefore vary.

An intermittent river (or ephemeral river) only flows occasionally and can be dry for several years at a time. These rivers are found in regions with limited or highly variable rainfall, or can occur because of geologic conditions such as having a highly permeable river bed. Some ephemeral rivers flow during the summer months but not in the winter. Such rivers are typically fed from chalk aquifers which recharge from winter rainfall. In the UK these rivers are called Bournes and give their name to place such as Bournemouth and Eastbourne

Uses

Leisure activities on the River Avon at Avon Valley Country Park, Keynsham, United Kingdom. A boat giving trips to the public passes a moored private boat. Many riverbanks in Japan are used as places for playing, recreation and parties

Rivers have been used as a source of water, for obtaining food, for transport, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.

Rivers have been used for navigation for thousands of years. The earliest evidence of navigation is found in the Indus Valley Civilization, which existed in northwestern Pakistan around 3300 BC.[7] Riverine navigation provides a cheap means of transport, and is still used extensively on most major rivers of the world like the Amazon, the Ganges, the Nile, the Mississippi, and the Indus. Since river boats are often not regulated, they contribute a large amount to global greenhouse gas emissions, and to local cancer due to inhaling of particulates emitted by the transports.[8][9]

In some heavily forested regions such as Scandinavia and Canada, lumberjacks use the river to float felled trees downstream to lumber camps for further processing, saving much effort and cost by transporting the huge heavy logs by natural means.

Rivers have been a source of food since pre-history.[10] They can provide a rich source of fish and other edible aquatic life, and are a major source of fresh water, which can be used for drinking and irrigation. It is therefore no surprise to find most of the major cities of the world situated on the banks of rivers. Rivers help to determine the urban form of cities and neighbourhoods and their corridors often present opportunities for urban renewal through the development of foreshoreways such as Riverwalks. Rivers also provide an easy means of disposing of waste-water and, in much of the less developed world, other wastes.

Fast flowing rivers and waterfalls are widely used as sources of energy, via watermills and hydroelectric plants. Evidence of watermills shows them in use for many hundreds of years such as in Orkney at Dounby click mill. Prior to the invention of steam power, water-mills for grinding cereals and for processing wool and other textiles were common across Europe. In the 1890s the first machines to generate power from river water were established at places such as Cragside in Northumberland and in recent decades there has been a significant increase in the development of large scale power generation from water, especially in wet mountainous regions such as Norway

The coarse sediments, gravel and sand, generated and moved by rivers are extensively used in construction. In parts of the world this can generate extensive new lake habitats as gravel pits re-fill with water. In other circumstances it can destabilise the river bed and the course of the river and cause severe damage to spawning fish populations which rely on stable gravel formations for egg laying.

In upland rivers, rapids with whitewater or even waterfalls occur. Rapids are often used for recreation, such as whitewater kayaking.

Rivers have been important in determining political boundaries and defending countries. For example, the Danube was a long-standing border of the Roman Empire, and today it forms most of the border between Bulgaria and Romania. The Mississippi in North America and the Rhine in Europe are major east-west boundaries in those continents. The Orange and Limpopo Rivers in southern Africa form the boundaries between provinces and countries along their routes.

Ecosystem

Main article: Lotic ecosystems

The flora and fauna of rivers use the aquatic habitats available, from torrential waterfalls through to lowland mires. Although many organisms are restricted to the fresh water in rivers, some, such as salmon and hilsa, have adapted to be able to survive both in rivers and in the sea. The organisms in the riparian zone respond to changes in river channel location and patterns of flow. For example, in rapidly migrating streams, ecological successions develop in accordance with the prevailing patterns of erosion and deposition.

Chemistry

Main article: River chemistry

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

Like many other aquatic ecosystems, rivers too are under increasing threat of pollution. According to a study of the WWF's Global Freshwater Programme, the 10 most polluted rivers are: Ganges, Indus, Yangtze, Salween-Nu, Mekong-Lancang, Rio Grande/Rio Bravo, La Plata, Danube, Nile-Lake Victoria, and the Murray-Darling.[11]

Brackish water

Further information: Brackish water Nile River delta, as seen from Earth orbit. The Nile is an example of a wave-dominated delta that has the classic Greek delta (Δ) shape after which River deltas were named. Photo courtesy of NASA.

Some rivers generate brackish water by having their river mouth in the ocean. This, in effect creates a unique environment in which certain species are found.

Flooding

Flooding is a natural part of a river's cycle. The majority of the erosion of river channels and the erosion and deposition on the associated floodplains occur during flood stage. In many developed areas, human activity has changed river channel form, altering different magnitudes and frequencies of flooding. Some examples of this are the building of levees, the straightening of channels, and the draining of natural wetlands. In many cases human activities in rivers and floodplains have dramatically increased the risk of flooding. Straightening rivers allows water to flow more rapidly downstream increasing the risk of flooding places further downstream. Building on flood plains removes flood storage which again exacerbates downstream flooding. The building of levees may only protect the area behind the levees and not those further downstream. Levees and flood-banks can also increase flooding upstream because of back-water pressure as the upstream water has to squeeze between the levees.

Flow

Direction

River meandering course

Rivers flow downhill from river source to river mouth, but they do not necessarily take the shortest path. For alluvial streams, straight and braided rivers have very low sinuosity and flow directly down hill, while meandering rivers flow from side to side across a valley. Bedrock rivers typically flow in either a fractal pattern, or a pattern that is determined by weaknesses in the bedrock, such as faults, fractures, or more erodible layers.

Rate

Volumetric flow rate, also called discharge, volume flow rate, and rate of water flow, is the volume of water which passes through a given cross-section of the river channel per unit time. It is typically measured in cubic meters per second (cumec) or cubic feet per second (cfs), where 1 m³/s = 35.51 ft³/s; it is sometimes also measured in litres or gallons per second.

Volumetric flow rate can be thought of as the mean velocity of the flow through a given cross-section, times that cross-sectional area. Mean velocity can be approximated through the use of the Law of the Wall. In general, velocity increases with the depth (or hydraulic radius) and slope of the river channel, while the cross-sectional area scales with the depth and the width: the double-counting of depth shows the importance of this variable in determining the discharge through the channel.

Management

Main article: River engineering

Rivers are often managed or controlled to make them more useful, or less disruptive, to human activity.

River management is a continuous activity as rivers tend to 'undo' the modifications made by people. Dredged channels silt up, sluice mechanisms deteriorate with age, levees and dams may suffer seepage or catastrophic failure. The benefits sought through managing rivers may often be offset by the social and economic costs of mitigating the bad effects of such management. As an example, in parts of the developed world, rivers have been confined within channels to free up flat flood-plain land for development. Floods can inundate such development at high financial cost and often with loss of life.

Rivers are increasingly managed for habitat conservation, as they are critical for many aquatic and riparian plants, resident and migratory fishes, waterfowl, birds of prey, migrating birds, and many mammals.

Rating systems

Gallery

Río Peralonso - El Zulia (Norte de Santander), Colombia.

River Gambia flowing through Niokolo-Koba National Park, Senegal.

Bridges are a common way of crossing rivers. (Hooghly River, Kolkata, India)

Zambezi and Victoria Falls in Zambia and Zimbabwe

Hooghly River, Kolkata, India.

Heathcote National Park, Australia.

This river flows from Woronora Dam, Sydney, Australia.

Oder River in Szczecin, Poland.

The entrance of Puerto Princesa Underground River in Palawan, Philippines.

A schematic showing how a freshwater river can be disconnected from a seawater mouth.

River behind Kundapur bus stop, Udupi, India

Arno river, Florence, Italy.

Smith River in fog, Henry County, Virginia.

See also

See also: geography, water cycle, and drainage basin
Look up river in Wiktionary, the free dictionary.
Wikimedia Commons has media related to: River

Crossings

Transport

References

  1. ^ River {definition} from Merriam-Webster. Accessed February 2010.
  2. ^ "WordNet Search: River". The Trustees of Princeton University. http://wordnetweb.princeton.edu/perl/webwn?s=river&sub=Search+WordNet&o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&h=. Retrieved 2009-10-02.
  3. ^ "Domestic Names: Frequently Asked Question (FAQs), #17". United States Geological Survey. http://geonames.usgs.gov/domestic/faqs.htm. Retrieved 2009-10-02.
  4. ^ Garde, R. J. (1995). History of fluvial hydraulics. New Age Publishers. pp. 19. ISBN 812240815X. OCLC 34628134. http://books.google.com/books?lr=&hl=en&q=%22It+may+also+be+mentioned+that+criterion+for+the+beginning%22.
  5. ^ Illies J. & Botosaneanu L. Problémes et méthodes de la classification et de la zonation éologique des eaux courantes, considerées surtout du point de vue faunistique. (1963)
  6. ^ Hawkes, H.A. (1975). River zonation and classification. Blackwell. pp. 312–374.
  7. ^ Panda.org
  8. ^ DOI.org
  9. ^ DOI.org
  10. ^ NMP.org
  11. ^ Top 10 most polluted rivers

Further reading

Categories: Rivers | Fluvial landforms | Geomorphology | Sedimentology | Water streams

 

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