Rivers


RIVERS

Rivers are Flowing Sources of Life

A river is a water body which begins in the mountain at an elevated height. It is a natural flowing water-course with a beginning, a middle and an end. It is usually made up of freshwater. In the English language, a river is also known as a ‘watercourse’, ‘waterway’, ‘stream’, ‘streamlet’, ‘tributary’, ‘brook’, ‘inlet’, ‘rivulet’, ‘runnel’, ‘run’, ‘freshet’, ‘canal’, ‘channel’, ‘burn’, ‘beck’, ‘bourn’, ‘creek’, ‘billabong’, ‘rarerillet’ and so on and so forth.

Every river starts at the highest point in a particular area as a minute trickle. As the trickle flows downstream, it gathers more and more water from other trickles, streams, springs, precipitation and other water resources.

The river flows usually towards and empties into an ocean, sea, another river or a lake. In some rare cases it flows and goes underground and at some rarer cases at the end of its course, the river becomes dry without reaching another water body, freshwater or saline. The main water-course is called the ‘river proper’ and the sides are called ‘banks’. The bottom of the river is called the ‘bed’. The scientific study of rivers is called Potamology.

Rivers are subject to the laws of nature and hence are a part of the hydrological cycle. As mentioned earlier, the main source of water in the river flow usually comes from precipitation through a drainage basin from the surface runoff, while other sources are ground water recharge, springs and the release of stored water in natural icepacks and snowpacks. There are nearly 17 countries in the world which do not have any river.

Rivers have had a great impact on the human civilization. Infact it can be said that rivers have helped humans become civilized. Rivers have also had a tremendous impact on religious practices, agriculture, industry and almost all aspects of human existence. River being water flowing is considered as a manifestation of God to help all living creatures. Many religious practices use water in their rituals. Many consider water bodies, especially rivers to be sacred and auspicious. Rivers as a concept, as a metaphor and a simile have been used far and wide in communication and art. In many cultures and religious practices, rivers have assumed the stature of living deities and are worshipped. The love of many for the river can be seen in our literature, music and plastic arts.


River Classification

For academic purposes rivers are classified. In fact, there a many types of river classifications, based on different criteria. Broadly speaking rivers are classified according to, the type of water they contain, a topographical classification, a morphological classification, a biotic classification, a classification according to the organisms they help sustain, so on and so forth.

River Topography and River Topographical Classification

River topography is the study and analysis of the distribution of water, the land that the river traverses, its relative position and ups and downs in relation to natural and manmade settings.
Like all things, there has to be a source of the river. As it has been mentioned, a river has a beginning, middle and an end. The river proper has many sources. The river proper follows a path called a river course and ends up at a mouth or mouths. Topographically the rivers can be in broad general sense be classified as alluvial, bedrock or a combination of the two in varying degrees. Rivers which have alluvial soil beds have channels and floodplains that are self-formed in unconsolidated or loosely consolidated sediment patches. These rivers erode and cut into the banks and deposit alluvial soil on the bars and their floodplains.

Whereas, the bedrock rivers are formed when the river proper, cuts through the newly formed sediments and the underlying bedrock. This phenomenon occurs in regions which have experienced some manner of steepening of the river gradients or in which a hard stone bed causes a river to have a steepened reach that has not been covered with newly formed alluvial soil.

It can also be seen that bedrock rivers very often contain alluvial soil on their beds, this kind of soil helps in eroding and finely sculpting the channel that the river flows through. Now, rivers that traverse through patches of bedrock and patches of alluvial soil can be safely classified as a combination river of bedrock and alluvial soil. Scientists also further classify alluvial rivers by their channel pattern, as a meandering, braided, wandering, anastomose or a straight. In the final analysis, the morphology of the reach of an alluvial river is determined by various factors such as sediment supply, substrate composition, discharge, vegetation and bed aggradation.

It was the American geographer and scientist William Morris Davis who at the start of the 20th century put forth the ‘cycle of erosion’ method of classifying rivers based on their “age”. Though, his method of analysis and classification of the rivers came in for immense criticism, there are many adherents to his river classification and school of thought.

Davis classified rivers into:

Youthful River: A youthful river has a steep gradient with very few tributaries and flows rather quickly. In this stage of the river, it flows along an uneven surface leading to extensive and intensive bottom erosion. It is the rapid deepening of the river channels that leads to the formation of the V shaped valleys. During the youthful stage of the river, the valley undergoes rapid and vigourous development in depth. During this stage there are the occurrences of lakes, rapids, waterfalls, steep-sided valleys and gorges. The phenomenon of river capture takes place. Youthful rivers have a long profile, rather irregular from source to mouth. Some of the examples of youthful river among others are Brazos, Trinity and Ebro rivers.

Mature River: According to Davis, a river with a gradient that is less steep than the youthful rivers and flows rather slowly is a mature river. The mature river flows with a rather graded profile and attains a profile of equilibrium. The landmass that the river flows through is very well dissected integrated and a very well integrated drainage system is developed. Ridges and valleys have developed prominently. This also leads to floodplains and the meandering of the river takes place. The topogra¬phy consists of features such as: hogbacks, cuestas, mesa, butte, meanders, oxbow lakes, natural bridges, flood plains, alluvial fans and so on and so forth. A mature river is fed by many tributaries and its channels erode wider rather than deeper. Some examples of mature rivers among many others are Parana, Thames, Mississippi, Danube, Ohio and Saint Lawrence.

Old River: An old river runs its course with a low gradient and has very low velocity of erosive energy. The old rivers flow in a sluggish manner. A lot of deposition of soil takes place. Old rivers have massive flood plains. The topography of the old river consist features of peneplains, natural levees, deltas and so on. Some of the examples of Old rivers are Huang Ho, Ganges, Tigris, Nile and Euphrates.

Rejuvenated river: Davis says that such a river is the one that has its gradient raised by a tectonic uplift. Each river is different and the manner in which a river’s finer points vary between the upper course and the lower course are summarized by the Bradshaw model of classification. Power-law connections between channel slope, depth and width are given as a function of discharge by ‘river regime’.

River Capture: Davis also mentions of river capture or river piracy. This in geographical terms means that when one of the two rivers flowing in the opposite direction from a single dividing point, becomes more effective in erosion due to a steeper gradient than the other river twin, the divide recedes dramatically towards the side with the smoother gradient. The water from the river with the smoother gradient goes to the one with the steeper gradient and begins to get drained through the channel of the first river. The process of diversion of a river by the head ward migration of another river is known as River-Capture or River-piracy. The point where the course of the second river is diverted is known as the Elbow of Capture. The captured river is known as Misfit and the deserted part of its channel through which no water flows is termed as the Wind-gap.

Biotic Classification of Rivers

River biotics means the interaction of the flora and fauna and the abiotic natural settings within and abutting the river.

Rivers are classified according to the organisms they contain, the kind of plants that grow in and on the banks of the river. Also, the natural aspects of the river influencing waters and in turn being influenced by them.

Rivers as we know are a natural phenomenon. Rivers consist of biotic and abiotic phenomena.

The biotic classification of rivers are as follows:

Primary Producers.
Herbivorous.
Carnivorous.
Omnivorous.
Decomposers.
Primary Producers: Primary producers are nothing but the green plants in the rivers. These plants prepare the food with the help of the sunlight, eg: green plant algae.

Herbivorous: These herbivorous organisms eat and depend upon the green plants that grow in the river, eg: small fish and insects in the river.

Carnivorous: The livelihood of these organisms depend upon other animals. They eat the flesh and bones of the other animals, eg : Shark.

Omnivorous: The organisms that eat both plants and animals are called omnivorous, eg: big fish.

Decomposers: When the living flora and fauna in the river die they are decomposed by the various bacteria and viruses present in the river water.



Rivers White Water Classification

The most widely used grading system of rivers is the international scale of river difficulty, where white water is classified into six different categories: from class I (the easiest and safest) to class VII (the most difficult and most dangerous.) The grade reflects both the technical difficulty as well as the dangers associated with a rapid; with grade referring to flat or slow-moving water with few hazards and grade VI referring to the hardest rapids which are very dangerous, even for expert paddlers and are the rarely run. Grade VI rapids are sometimes downgraded to minus V or V plus if they have been run successfully. A portage rapid is where the boat lands and carries the boat around the hazard. A rapid grade is not fixed since it may vary greatly depending on the depth of water and speed of flow. Although, some rapids may be easier at high flow because features are covered or washed out, high water usually makes rapids more difficult and dangerous.
The river white water classification is as follows:
Class I : very small rough areas requires no maneuvering.

Class II : Some rough water, may be some rocks, small drops and might require maneuvering. (Skill level, basic paddling skill)

Class III: Medium waves, maybe a 3-5 ft drop, but not much danger. May require significant maneuvering.

Class IV: White water, large waves, long rapids, rocks, maybe a considerable drop. Sharp maneuvers may be needed.

Class V: White water large waves, continuous rapids, large rocks and hazards. May be a large drop, precise maneuvering, often characterised by “must make move” i.e failure to execute a specific maneuver at a specific point mass, resulting in serious injuries or death. Class V is sometimes expanded to Class V+, that describes the most extreme runnable rapids.

Class VI: While there is some debate over the classification Class VII, in practice it refers to rapids that are not passable and any attempt to do so would result in serious injuries, near drowning or death.



River Stream Order Classification

The stream order hierarchy was officially proposed in 1952 by Arthur Newell Strahler, a geo-science professor at Colombia University, in New York city, USA, in his article Hypsometric (area altitude) analysis of erosional topology. The article which appeared in the Geological Society of America bulletin outlined the order of streams and a way to define the size of perennial and recurring streams. When using stream order to classify a stream, the size or range from a first order stream all the way to the largest, a 12th order stream.

A first order stream is the smallest of the world’s streams and consists of small tributaries. These are the streams that flow into and feed larger streams, but do not normally have any water flowing into them. In addition, Ist and IInd order streams generally form on steep slopes and flow down, until they slow down and meet the next order waterway. First to third order streams are also called headwater streams and constitute waterways in the upper reaches of the watershed. It is estimated that over 80 pc of the world’s water ways are these Ist to IIIrd order water ways or head water streams.
Going up in size and strength, streams that are classified as IVth through VIIth order are medium streams, while anything larger (upto 12th order) is considered a river. For eg, to compare the relative size of these different streams, the Ohio river in the USA is an 8th order stream, while the Mississippi river is a 10th order stream. The world’s largest river: the Amazon in South America is considered a 12th order stream. Unlike the smaller order stream, these medium and larger rivers are usually less steep and flow slowly. These streams however tend to have larger volumes of runoff and debris as it collects in them from the smaller waterways flowing into them.

Components of a River

It is now clear that a river as we know is part of a larger system, that is a watershed, which is land-drained by a river and its tributaries. Rivers are large natural streams of water flowing in channels and emptying into larger bodies of water.

The components of the river are, the river bed, river bank, floodplains and so on. The river is considered as the mother lode of resources. Other aspects of the river are its temperature, salinity, floating debris, silt, mud and so on. The river also hosts natural resources like iron ore, gold nuggets, manganese, uranium, thorium, potassium, sulphur as well as a wide variety of flora and fauna.



River Bed

It is the way of river flow. Through the bed the river flows. Each river has its own river bed through which it flows. The river bed means, in which direction the river will flow. In rapids, the river bed is very small. The water flow is little quantitatively. Its river bed is also smaller. In waterfalls, the water flows from the highest point. Here the water flows speedily and water flowing is also large. The river bed is smaller because it flows in rugged topography at 0+ bow lake. The river bed is larger because it flows in plain area.



River Bank

The river bank forms by the deposition work of the river. On the shape of the bank the river flows. On the nature of the flow of the river, the river bank gets formed. The nature of the river bank depends upon the river deposition, slow movement of the river and silt deposited as well as debris are also deposited on the flow nature of the river. Often at river banks more than sand, silt is deposited due to plain topography. River bank shape differs from the nature of the river flow. The bank of the river will be formed due to the sluggish movement of the river.



Floodplains

Floodplains are formed during the floods as the river deposits debris like soil, silt and sand. The plains that are formed are known as floodplains. When flood occurrs at the plain area, new soil with high fertility is deposited on the old soil layer. The flood occurring region forms the flood plain. Floodplain soil is highly fertile than the other plain soil, because the soil changes every year. The production of crops is more than the other plain regions. This plain is very fertile and yields more and different crops.



River Formation

River formation is a natural phenomenon. River formation takes place only by natural ways only. The river is formed due to the rain water, glaciers as well as by the waters underground. Thus, rivers are formed by joining of stream gullies and rivulets. By the natural droplets of the water, the river comes into existence. By high melting snow, rainfall, the river comes into existence. We should note again that rivers are formed by natural processes and not by any other processes.

Uses of Rivers

Rivers have various uses for mankind, for flora and fauna of the planet. Water is life after all. The important uses of the river are as follows:

Rivers are used for navigation to reach from one point to another.

Rivers are rich in ore that if mined can yield iron, gold, silver, potassium, manganese among others.

Rivers are the source of food for the flora and fauna and humans.

River water is used by mankind for various purposes.

Rivers are centres for recreation and practice of religion.

Rivers are the creators of civilizations and cities are developed on the banks of the great rivers of the world.

Rivers can be used to produce electricity.

Rivers are the major source of irrigation for farming purposes.

Rivers are the veritable habitats for various aquatic organisms.

Rivers temper the climate.

Rivers nourish Mankind and all the members of the plant and animal kingdom.

River Ecosystem

The ecosystem of the river is the ‘river viewed as a system operating in its natural environment’ and includes biotic (living) interactions among plants, animals and micro-organisms as well as abiotic (non-living) physical and chemical.



Abiotic factors

Rivers: Water flow is the key factor in abiotic system influencing their ecology. The strength of water flow can vary between systems ranging from torrential rapids to slow-back waters that almost seem like lentic systems. The flow of the water speed can also vary within a system.

Light: Light is important to abiotic systems because it provides the energy necessary to drive primary production via photosynthesis and can also provide refuge for prey species in shadow.

Temperature: Most abiotic species are poikilothermy whose internal temperature varies with their environment, thus temperature is a key abiotic factor for them.

Chemistry: Water chemistry between systems varies tremendously. The chemistry is foremost determined by inputs from the geology of its watershed or catchment area that can also be influenced by precipitation and the addition of pollutants from human sources.

Substrate: The inorganic substrate of abiotic systems is composed of the geologic material present in the catchment that is eroded, transported, sorted and deposited by the current. Inorganic substrate are classified by size, on the Wentworth scale, which ranges from boulders to pebbles to gravel to sand and to silt.

Biotic Factors

Bacteria: Bacteria are present in large numbers in lotic waters. Fresh living forms are associated with decomposing organic material, bio-film on the surface of the rock and vegetation in between particles that compose the substrate and those that are suspended in the water column.



Primary Producers

Algae consisting of phytoplankton and periphyton are the most significant sources of primary production in most streams and rivers.

Insects and Other Invertibrates

Upto 90 pc of the invertibrates in some lotic system are insects. These species exhibit tremendous diversity and can be found occupying almost every available habitat including the surfaces of stones deep below the substratum, adrift in the current and in the surface film.

Fish and other Vertibrates

Fish are the best known inhabitants of lotic systems. The ability of the fish species to live in flowing water depends upon the speed with which it can swim and the duration that the speed can be maintained.



River Chemistry

The chemical characteristics of water are studied in aquatic ecosystems for multiple reasons.

In pristine condition they define the ambient qualities in which the aquatic biota has developed as in rivers, lakes and wetlands.

In conditions altered by human activities these correspond to environment pressure on aquatic species.

Riverine fluxes of organic carbon, nutrients and toxic substances to enclosed waterbodies such as lakes and reservoirs and to the coastal zones determine the state of oxygenation, eutrophication and exposure to harmful substances.

Over a period of time, the water chemistry of all waterbodies has indeed been changing. The change has been glaring and very rapid after the scientific revolution. The impact on water chemistry and its components has been due to natural reasons and the various activities of mankind.

River chemistry can be classified with regard to the material in the water (solubles, gas, colloids, suspended particles and so on. Heim and Chapman are the scientists who have done detailed work regarding water quality in ground water, streams, ponds, reservoirs, lakes and rivers. The chemical characteristics of the water are those determined by the analyst at that period of time. Analyses of water are performed with regular monitoring in short frequencies by taking discrete water samples. While ideally the sampling and analysis should be continuous in space and time and peformed on the hundreds of elements/parameters, three types of analysis are peformed generally. They are 1) on unfiltered water as total phosphorous (Tot P) and organic carbon (TOC) 2) On waters conventionally filtered at 0.45 or 0.5 um, defining content dissolved concentration4 which actually may contain parts of the colloids and TTS on suspended particulates.



Brackish Water

Brackish water or brine water has more salinity than fresh water, but not as much as sea water. The reason may be the meeting of sea water with fresh water as in the case of estuaries, or it may be due to64 brackish fossil aquifers. The word brackish comes from the Middle Dutch root ‘Brak’.

Certain human activities can produce brackish water, in particular civil engineering projects such as dykes. Also, brackish water is produced by the flooding of coastal marshland which is used for prawn and lobster cultivation. Brackish water is also the primary waste product of the salinity gradient power processes. Brackish water is hostile to the growth of most terrestrial plant species. Technically, brackish water contains between 0.5 and 30 gms of salt per litre – more often expressed as 0.5 to 30 parts per thousand (0/00) which has a specific gravity between 1.005 and 1.010.



River Flooding

River flooding is formed due to heavy rainfall, obstacles at flow of direction of the river. The silt formed due to the soil erosion is in turn formed due to deforestation, unscientific cultivation and so on. The level of the river increases thereby inducing flooding.



Effects of River Pollution

The effects of pollution on rivers has been disastrous for Mankind, flora and fauna. Its impact has been so devastating that it has changed the quality of life for everyone.

Pollution has had an effect on rivers so much so that the original colour of the rivers which was supposed to be crystal clear and to much of a degree transparent, has now become blackish, brownish and reddish in colour.

Many diseases that affect humans, animals and plants can be attributed to the pollution of rivers. Many of such diseases are contagious in nature.

Due to the pollution of rivers there is continuous foul smell in certain parts of the river where the pollution level is intense.

When polluted waters of the rivers are used for irrigation, the quality and quantity of the yield suffers.

Use of polluted river water decreases the fertility of soil.

Polluted river waters are unfit for drinking and domestic use.



Rivers of the World

Rivers of North America are many and among them, stand out the Missisippi-Missouri drainage system. This drainage system is the world’s third longest and 10th largest. It is 6,270 km and the catchment area touches 31 states of the USA and provinces of Canada. The Mackenzie river is the largest and longest river of Canada. Its length is 4,241 sq km.

The Colorado river in the US lies in the southwest. It is 2,330 km long. It forms a deep gorge named as the Grand Canyon.

The Columbia river is 2,000 km long. It has a tributary named Snake. It is the Northwest US’s main river.

The St Lawrence river is associated with the Niagara waterfalls between Canada and the United States of America. The Niagara is shaped like a horse foot.

In South America the mighty Amazon, Orinaco, Sao Francisca, Parague rivers can be mentioned.

The Amazon is the largest river in the world. It has 40 percent of South America catchment area. It is the world’s second longest river after the Nile. It is 6,448 sq km in length. Putumayo, Maranon, Japura/Caqueta Rio Negro, Guainia, Ucayali, Purus, Madeira, Tapajos, Xingu, Trombetas, Parana, are the tributaries of the Amazon.

The Orinoco is 2,740 sq km in length. It is the second largest river of South America. It has 8,80,000 sq km of catchment area in Venezuela and Colombia. The Angel waterfall is caused by the Orinoco. Its main tributary is tributaries is Apure. The other tributaries are Arauca, Bita, Rio Capanaparo, Caroni, Caura, Cinaruco, Guaviare, Guayabero, Meta, Sipapo, Tupparo,Ventuari, Yocoima. Sao Francisca is the 4th largest river of South America.

In Europe the Olga is the largest and longest river. It is 3,690 km long.

In Central and Eastern Europe it is the Danube that is the main river. It flows to a distance of 2,870 sq km. The Danube river is known as the Gate of South East Europe.

The Ural river runs through Russia and Kazakhistan and is one of the major rivers of that region. The Ural river also demarcates the boundaries of the two countries.

The Ebro river is the most important river in Spain. It has 85,500 sq km length of catchment area.

The Rhone river is also one of the most important rivers of Europe. Its length is 813 sq km. Its catchment area is 98,000 sq km.

The Rhine river flows to an area of 1,230 sq km and its catchment area is 2.2 mn sq km.

The Po river is an important river of Italy. The main tributaries of the river Po are: Adda, Agogna, Arda, Brembo, Crostoto, Curone, Dora Ballea, Grana Del Monterrato, Lambro, Maira, Malone, Mincio, Nure, Oglio, Orco, Parma, Pelice, Rotaldo, Sangone, Scrivia, Secchia, Sesia, Stura, Di Lanzo, Tanaro, Taro, Terdopplo, Ticino, Tidone, Trebbia, Varaita,

The Loire river is an important river of France. It flows at an area of 1,002 sq km. The important tributaries of the river Loire are: Sevre Nantaise (in Nantes), Erde (in Nantes), Evre (in Le Marillais), Layon (in Chalonnes-sur-Loire), Maine (near Angers), Mayenne (near Angers), Oudon (in Le Lion D’ Angers), Verzee (in Segre) Ernee (in Saint Jean sur Mayenne), Sarthe (near Angers), Loir (north of Angers), Brave (in Pont-de-Brave, Aigre (near Cloyes Sur-le Loire), Yerre (near Cloyes sur-le-Loir), Conie (near Chateaudun) Ozanne (near Bonneval), Vaige (Sable sur-Sarthe) , "Conie (page does not exist)" Conie "Châteaudun" Châteaudun), " \o "Ozanne" Ozanne " "Bonneval, Eure-et-Loir" Bonneval)”, "Vaige" Vaige " "Sablé-sur-Sarthe" Sablé-sur-Sarthe), "Vègre" Vègre "Avoise" Avoise), "Huisne" Huisne “ "Le Mans" Le Mans) "Thouet" Thouet “ "Saumur" Saumur), "Dive (river)" Dive (near "Saint-Just-sur-Dive" Saint-Just-sur-Dive), "Losse (Thouet) " Losse (near "Montreuil-Bellay" Montreuil-Bellay), "Argenton (river)" Argenton "Saint-Martin-de-Sanzay" Saint-Martin-de-Sanzay), "Thouaret" Thouaret” "Taizé, Deux-Sèvres" Taizé), "Cébron” " Cébron "Saint-Loup-sur-Thouet" Saint-Loup-sur-Thouet), "Palais (river) " Palais "Parthenay" Parthenay), "Viette (river) " Viette (near Parthenay), "Vienne (river)" Vienne "Candes-Saint-Martin" Candes-Saint-Martin), "Creuse (river)" Creuse (north of "Châtellerault" Châtellerault), "Gartempe" Gartempe "La Roche-Posay" La Roche-Posay), "Anglin" Anglin "Angles-sur-l'Anglin" Angles-sur-l'Anglin), "Salleron" Salleron "Ingrandes, Indre" Ingrandes), "Benaize" Benaize "Saint-Hilaire-sur-Benaize" Saint-Hilaire-sur-Benaize), "Abloux" Abloux "Prissac" Prissac), "Brame" Brame "Darnac" Darnac), "Semme" Semme "Droux" Droux),” "Petite Creuse" Petite Creuse” "Fresselines" Fresselines”, "Clain" Clain (in Châtellerault), "Clouère" Clouère "Château-Larcher" Château-Larcher), "Briance" Briance "Condat-sur-Vienne" Condat-sur-Vienne), "Taurion" Taurion "Saint-Priest-Taurion" Saint-Priest-Taurion), "Indre (river)" Indre (east of Candes-Saint-Martin), "Indrois" Indrois "Azay-sur-Indre" Azay-sur-Indre), "Cher (river)" Cher "Villandry" Villandry), "Sauldre" Sauldre "Selles-sur-Cher" Selles-sur-Cher), HY "Rère" Rère "Villeherviers" Villeherviers "Arnon (river)" Arnon (near "Vierzon" Vierzon), "Yèvre" Yèvre (in Vierzon), "Auron (river)" Auron (in "Bourges" Bourges), "Airain" Airain (in "Savigny-en-Septaine" Savigny-en-Septaine), "Tardes (river)" Tardes (in "Évaux-les-Bains" Évaux-les-Bains), "Voueize" Voueize (in "Chambon-sur-Voueize" Chambon-sur-Voueize), "Beuvron (Loire)" Beuvron (in "Chaumont-sur-Loire" Chaumont-sur-Loire), "Cosson" Cosson (in "Candé-sur-Beuvron" Candé-sur-Beuvron), "Loiret (river)" Loiret (in "Orléans" Orléans), "Vauvise" Vauvise (in "Saint-Satur" Saint-Satur), "Allier (river)" Allier (near "Nevers" Nevers), "Sioule" Sioule (in "La Ferté-Hauterive" La Ferté-Hauterive), "Bouble" Bouble (in "Saint-Pourçain-sur-Sioule" Saint-Pourçain-sur-Sioule), "Dore (France)" Dore (near "Puy-Guillaume" Puy-Guillaume), "Alagnon" Alagnon (near "Jumeaux" Jumeaux), "Senouire" Senouire (near "Brioude" Brioude), "Ance River (page does not exist)" Ance (in "Monistrol-d'Allier" Monistrol-d'Allier), "Chapeauroux" Chapeauroux (in "Saint-Christophe-d'Allier" Saint-Christophe-d'Allier), "Nièvre (Loire)" Nièvre (in "Nevers" Nevers), "Acolin" Acolin (near "Decize" Decize), "Aron (Loire)" Aron (in "Decize" Decize), "Alène" Alène (in "Cercy-la-Tour" Cercy-la-Tour), "Besbre" Besbre (near "Dompierre-sur-Besbre" Dompierre-sur-Besbre), "Arroux" Arroux (in "Digoin" Digoin), "Bourbince" Bourbince (in "Digoin" Digoin), "Arconce" Arconce (in "Varenne-Saint-Germain" Varenne-Saint-Germain), "Lignon du Forez" Lignon du Forez (in "Feurs" Feurs), "Furan (river)" Furan (in "Andrézieux-Bouthéon" Andrézieux-Bouthéon) and "Lignon du Velay" Lignon du Velay (in "Monistrol-sur-Loire" Monistrol-sur-Loire).

The African continent has many wonderful rivers. The Nile river is the longest river in the world. The Blue Nile, White Nile, Yellow Nile, Atbara, Bar El Ghazal, Sobhat, Wadi Mur, Tekeze, are the major tributaries of the Nile river. The Aswan dam was constructed across the Nile to control the flow of the waters.

The Congo river is also known as the Zaire river. It has a length of 4,700 sq km and has a catchment area of 4 mn sq km. The main tributaries of the Congo are "Inkisi River" Inkisi, "Kasai River" Kwa-Kassai, "Fimi River" Fimi, "Lukenie River" Lukenie, "Kwango River" Kwango, "Sankuru River" Sankuru, "Lefini River" Lefini, "Sangha River" Sangha, "Kadéï River" Kadéï, "Ubangi River" Ubangi. "Mbomou River" Mbomou "Uele River" Uele, "Tshuapa River" Tshuapa, "Lomami River" Lomami River, "Luvua River" Luvua, "Luapula River" Luapula and "Chambeshi River" Chambeshi. Upstream of "Boyoma Falls" Boyoma Falls near "Kisangani" Kisangani, the river Congo is known as the "Lualaba River" Lualaba River.

The Niger river is West Africa’s most important river. Its length is 4,180 sq km. It is the third largest river of Africa after the Nile and the Congo. Its tributary is the Benue.

The Zambezi river is the 4th largest river of the African continent and flows into the Indian Ocean. The length of its flow 2,374 sq km. The Victoria, Chvuma, Ngonge waterfalls are formed by the Zambezi.

The Orange river is South Africa’s longest river. It flows at a length of 2,100 sq km. It has a tributary named Vaal.

In Asia, many major rivers flow. Some of them are as follows: the Yangtze Kiang, Huang Ho, Ob, Lena, Amur, Mekong, Menam, Irrawaddy, Salwean, Euphrates, Tigris, Yenesei, Bosphorus, Indus, Jhelum, Chenab, Ravi, Beas, Sutlej, Brahmaputra, Ganga, Yamuna, Ghagra, Banganga, Gandhak, Kosi, Gomati, Damodar, Mahanadi, Godavari, Krishna, Ghataprabha, Malaprabha, Tungabhadra, Betwa, Cauvery, Narmada, Tapti, Sharavati and Kali.

Rivers of the Indian Sub-continent

The Indian sub-continent is mainly divided two geographical parts: north India and south India.

Of the north Indian rivers, the main ones are: Indus, Ganga and Brahmaputra. The Indus flows for a short time through the territory of the Republic of India and the rest through the Islamic Republic of Pakistan. The main sub-rivers or tributaries are the Jhelum, Chenab, Ravi, Beas and the Sutlej.

The Ganges is the longest river in the sub-continent and is one of the cradles of the Hindu civilization. It is a sacred river for people of many religions. Its main tributaries are the Banganga, Ghaghara, Gandak, Kosi, Yamuna, Sharada and Damodar.

The Brahmaputra is considered as a male river of the sub-continent. Its tributaries are the, Dibang "Lohit River" Lohit,” "Dhansiri River" Dhansiri, "Kolong River" Kolong , "Kameng River" Kameng River, "Manas River" Manas "Raidak River" Raidak "Jaldhaka River" Jaldhaka, "Teesta River" Teesta, "Subansiri River" Subansiri

In the southern half of the sub continent of India, there are two main divisions: the east flowing rivers and the west flowing rivers. The east flowing rivers are the Mahanadi, Godavari, Krishna, Cauvery Suvarnarekha, Bhaitarani, Brahmani and Koel.

The Mahanadi is known as the sorrow of Orissa due to the floods that the river causes. So, the Hirakud dam was constructed and is now considered as the longest dam in India. Its tributaries are Seonath, Mand, Ib, Hasdeo and Telen, Parry, Jonk and Ong.

The Godavari is the largest river running in the southern part of India Its main tributaries are the Sabari, Indravati and Manjra.

The Krishna is the second largest river in south India. Its main tributaries are the Tunga, Bhadra, Bhima, Ghataprabha, Yerla, Panchaganga and Doodganga.

The Cauvery river is known as the “youthful Ganges”. Its main tributaries are Lakshmanteerth, Kabini, Hemavati, Lokapavani, Shimsha, Arakavati, Honnuhole, Bhavani, Noyyal and Amaravati.

Of the west flowing rivers, the Narmada is the longest river. Its main tributaries are Dudhi, Tawa, Urhner, Banjar, Sher, Shakkar, Ganjal, Chhota Tawa, Kundi, Goi and Karjan.

The Tapti or Tapi is the second largest river of the west flowing rivers. Its main tributaries are the Girna, Purna, Panzara, Bori, Waghur, Aner and Gomai.

The Sharavati river has the world famous Jog Falls in the Shimoga district of Karnataka.

The Periyar is the most important river of ‘God’s own Country’, Kerala.

River and Society

Throughout the world, in the recorded history of Mankind, all civilizations have emerged and flourished on the banks of great rivers. Famous civilizations like the Harappa and Mohenjo Daro on the banks of the Indus, the Mesopotamian civilization on the banks of the Euphrates and Tigris, the Egyptian civilization on the banks of the Nile are great examples to denote. Human civilization has reached its epitome thanks to the rivers on the banks of which it survived and thrived. The river is the gift to human civilization. Infact, it is said that the whole of Egypt is the gift of the Nile. If not for the Nile river, there would be no Egyptian empire or civilization or the Egyptian people.

Various human activities and needs are connected to the river. Of them the most important is agriculture. The others are fishing, transportation, recreation, religion etc. Nutrients for Man, fauna and flora are derived from a healthy river. Hence, it is the duty of Mankind to preserve the health of the rivers and other water bodies. In the Hindu traditions rivers are given the status of Gods and Goddesses.



River Flow

River flow depends upon the slope of the relief. Rivers as we know follow the laws of gravity and flow from the top of the mountains through the mountains to the plains, until they reach the sea. The flow of the river from the mountains to the plains is divided into upper, middle and lower course. The whole pathway of the river is called the course of the river. The flow of the river performs three activities, known as erosion, transportation and deposition. The velocity of the river flow depends upon the slope of the relief. At the steep slope and rapid decline, the velocity of the river is very high. At a relatively moderate slope it is medium and as the radiant becomes gentler, the velocity too lessens.



River Products

The river is mainly large quantities of fresh water flowing from one point to the other. As the main ingredient of the river is water, it is one of the most important aspects of the landscape for Man.

The products that the river gives directly and indirectly are very vast and priceless. To a large extent human life and activity depends on fresh water and rivers are the bountiful source of it. The river abounds in many creatures that Man consumes. Of them fish is very important and comes to immediate mention. A number of aquatic creatures are harvested for food. Among them are crabs, shrimps, fish etc. A large number of ores are mined from the rivers. Also, the river is the large deposit of sand. Among the elements mined from the river are, iron, gold, manganese, petroleum etc. Rivers also offer beautiful recreational spots. Of late rivers are being utilized to the fullest to produce electricity.



River Seepage

River seepage is the slow escape of water through the ground to fill up water tables. Infact, modern scientists are looking at ways and means to optimally utilize the water available above the surface for the purposes of irrigation, industry and domestic use. The amount of water seepage and wastage through other unscientific behavior around the world, is phenomenal. The rampant use of ground water has lowered the water tables and it is inevitable that above surface water due to gravity has to “seep in” and fill up the water table. This effects the flow of quantity of water and also in turn affects the climatic conditions and the ecology as a whole. Optimal use of above surface water will wean us away from overexploiting underground water reserves.



River Sediment Yields

River sediment yield can be defined as the amount of material eroded from the land surface by the water runoff and delivered to a stream system. According to UK scientist Sue White, river sediment yield can be defined as the amount of sediment reaching or passing a point of interest in a given period of time and sediment yield estimates are normally given as metric tonnes or kilograms per year. In estimating sediment yield, we are taking a slice of a part of the sediment cycle and examining a particular point of interest to see how variability in the sediment cycle upstream of this point presents itself in terms of sediment delivery over time. It has been a long practice of requiring sediment yield estimates as part of the study for a proposed dam or a barrage over a river or stream. An average annual sediment yield estimate was considered sufficient for the purpose till now.

But, even a yearly estimate of sediment yield has proven to be difficult to achieve. It has been a fact that many scientific estimates have proven to be off the mark and many reservoirs have been seen to be losing storage capacity at a rate far exceeding than that of what was estimated before the dam or barrage was constructed. These days, sediment yield estimates are required as part of assessments of the amount of sediment yields and delivery of sediments and contaminants to the estuarine or the ocean system.