River capture
Encyclopedia
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
phenomenon occurring when a stream or river drainage system
Drainage system (Geomorphology)
In geomorphology, a drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land, whether a particular region is dominated by hard or soft rocks, and the gradient of the land. Geomorphologists and...
or watershed
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
is diverted from its own bed, and flows instead down the bed of a neighbouring stream. This can happen for several reasons, including:
- Tectonic earth movements, where the slope of the land changes, and the stream is tipped out of its former course.
- Natural damming, such as by a landslideLandslideA landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
or ice sheetIce sheetAn ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
. - ErosionErosionErosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
, either- Headward erosionHeadward erosionHeadward erosion is a fluvial process of erosion that lengthens a stream, a valley or a gully at its head and also enlarges its drainage basin. The stream erodes away at the rock and soil at its headwaters in the opposite direction that it flows. Once a stream has begun to cut back, the erosion is...
of one stream valley upwards into another, or - Lateral erosion of a meanderMeanderA meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
through the higher ground dividing the adjacent streams. - Within an area of karst topographyKarst topographyKarst topography is a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite, but has also been documented for weathering resistant rocks like quartzite given the right conditions.Due to subterranean drainage, there...
, where streams may sink, or flow underground (a sinking or losing streamLosing streamA losing stream, or influent stream, is a stream or river that loses water as it flows downstream. The water infiltrates into the ground recharging the local groundwater, because the water table is below the bottom of the stream channel...
) and then reappear in a nearby stream valley.
- Headward erosion
The additional water flowing down the capturing stream may accelerate erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
and encourage the development of a canyon
Canyon
A canyon or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of...
(gorge).
The now-dry valley of the original stream is known as a wind gap.
Tectonic uplift
- Barmah Choke
- About 25,000 years BPBefore PresentBefore Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
, an uplift of the plains near Moama first dammed the Murray RiverMurray RiverThe Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
and then forced it to take a new course. The new course dug its way through the so called Barmah Choke and captured the lower course of the Goulburn RiverGoulburn RiverGoulburn River may refer to:* Goulburn River , Australia* Goulburn River , Australia...
for 500km.- Barrier Range
- The original course of the Murray RiverMurray RiverThe Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
was to a mouth near Port Pirie where a large delta is still visible protruding into the calm waters of Spencer GulfSpencer GulfThe Spencer Gulf is the westernmost of two large inlets on the southern coast of Australia, in the state of South Australia, facing the Great Australian Bight. The Gulf is 322 km long and 129 km wide at its mouth. The western shore of the Gulf is the Eyre Peninsula, while the eastern side is the...
. An uplift of the land blocked the river near the southern end of the Flinders RangesFlinders RangesFlinders Ranges is the largest mountain range in South Australia, which starts approximately north west of Adelaide. The discontinuous ranges stretch for over from Port Pirie to Lake Callabonna...
, and the river eventually found its way to a new mouth near Lake AlexandrinaLake Alexandrina (South Australia)Lake Alexandrina is a lake in South Australia adjacent to the coast of the Southern Ocean, about 100 kilometres south-east of Adelaide.-Name:The lake was named after Princess Alexandrina, niece and successor of King William IV of Great Britain and Ireland...
.
Glacial damming
- The River Thames in southern EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
originally entered the North SeaNorth SeaIn the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
near IpswichIpswichIpswich is a large town and a non-metropolitan district. It is the county town of Suffolk, England. Ipswich is located on the estuary of the River Orwell...
. About 450,000 years BPBefore PresentBefore Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
, an ice sheetIce sheetAn ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
expanding from the north pushed the course of the river southwards, forcing the Thames to cut a new mouth where the mouth of the River Blackwater, EssexRiver Blackwater, EssexThe River Blackwater is a river in England. It rises in the northwest of Essex as the River Pant and flows to Bocking, near Braintree, from where its name changes to the Blackwater. Its course takes it near Stisted, and then via Bradwell Juxta Coggeshall and Coggeshall and near Witham where it is...
now is, north of London. It later moved southwards again to its current position as a result of cutting through the Chiltern HillsChiltern HillsThe Chiltern Hills form a chalk escarpment in South East England. They are known locally as "the Chilterns". A large portion of the hills was designated officially as an Area of Outstanding Natural Beauty in 1965.-Location:...
at Goring-on-ThamesGoring-On-ThamesGoring-on-Thames is a large village and civil parish on the River Thames in South Oxfordshire, about south of Wallingford.-Geography:...
, an event which created the Goring GapGoring GapThe Goring Gap is a British geological feature located on the River Thames approximately 8 miles upstream from Reading.Half a million years ago the River Thames flowed on its existing course through Oxfordshire, but then turned northeast to flow through Hertfordshire before eventually reaching the...
.
Headward erosion
- The Teays RiverTeays RiverThe Teays River was an important preglacial river that drained much of the area now drained by the Ohio River, and more. Traces of the Teays across northern Ohio and Indiana are represented by a network of river valleys. These valleys were carved in the late Cenozoic and eventually led to the...
, captured by the Ohio RiverOhio RiverThe Ohio River is the largest tributary, by volume, of the Mississippi River. At the confluence, the Ohio is even bigger than the Mississippi and, thus, is hydrologically the main stream of the whole river system, including the Allegheny River further upstream...
. - The Rio GrandeRio GrandeThe Rio Grande is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico – United States border. Its length varies as its course changes...
which before capture flowed into a closed basin, Lake Cabeza de Vaca, but after capture flowed into the Gulf of MexicoGulf of MexicoThe Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
. - The River Stour, KentRiver Stour, KentThe River Stour is the river in Kent, England that flows into the English Channel at Pegwell Bay. Above Plucks Gutter, where the Little Stour joins it, the river is normally known as the Great Stour. The upper section of the river, above its confluence with the East Stour at Ashford is sometimes...
, largely captured by the River BeultRiver BeultThe River Beult is a tributary of the River Medway. It has several sources west of Ashford, including one at Woodchurch. It then flows through Headcorn. At Hunton, above Yalding it is joined by the major stream of the River Teise. Town bridge lies 10¼ miles from Allington, it is the longest...
ˈ, River TeiseRiver TeiseThe River Teise is a tributary of the River Medway in Kent, England. It begins in Dunorlan Park in Tunbridge Wells. and flows eastwards past Bayham Abbey and then through Lamberhurst...
ˈ and others. - The River WeyRiver WeyThe River Wey in Surrey, Hampshire and West Sussex is a tributary of the River Thames with two separate branches which join at Tilford. The source of the north branch is at Alton, Hampshire and of the south branch at both Blackdown south of Haslemere, and also close to Gibbet Hill, near Hindhead...
, in southern EnglandEnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, the western arm of which is the former upper waters of the River Blackwater (River Loddon)River Blackwater (River Loddon)The River Blackwater is a tributary of the River Loddon in England and, indirectly, of the River Thames. It rises at Rowhill on the outskirts of Aldershot between Aldershot in Hampshire and Farnham in Surrey and runs northwards to join the Loddon near the village of Swallowfield in Berkshire...
. - The River Rheidol in WalesWalesWales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
which has captured the headwaters of other streams and now runs for part of its length in a deep gorge. - The River LydRiver Lyd (Devon)The Lyd is a river rising at Lyd Head in the Dartmoor national park in Devon in south-west England and flowing into the River Tamar beyond Lifton.-Lydford Gorge:...
in DevonDevonDevon is a large county in southwestern England. The county is sometimes referred to as Devonshire, although the term is rarely used inside the county itself as the county has never been officially "shired", it often indicates a traditional or historical context.The county shares borders with...
, England. - Vlara Moravia; Czech Republic
Karst
- The Donauversickerung (Danube SinkDanubeThe Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....
), currently developing in GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, where a large portion of the upper parts of the DanubeDanubeThe Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....
river sinks into the limestoneLimestoneLimestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
bedrock, and resurfaces in the AachtopfAachtopfThe Aachtopf is Germany's biggest natural spring, producing an average of 8,500 litres per second. Production varies seasonally and in response to the weather, but the spring never runs dry...
springSpring (hydrosphere)A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...
, a tributary of the River Rhine.
Effect on freshwater life
River capture is a shaping force in the biogeographyBiogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
or distribution of many freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
species.
Australian freshwater fish
AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
provides a particularly fascinating series of examples of freshwater fish species and distributions resulting from river capture events. The formerly massive Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...
runs the length of the eastern coastline of Australia and has isolated native freshwater fish populations east and west of the range for millions of years. In the last two million years erosion has reduced the Great Dividing Range to a critical point where west-to-east river capture events have been possible. A number of native fish species that originated in the Murray
Murray River
The Murray River is Australia's longest river. At in length, the Murray rises in the Australian Alps, draining the western side of Australia's highest mountains and, for most of its length, meanders across Australia's inland plains, forming the border between New South Wales and Victoria as it...
-Darling
Darling River
The Darling River is the third longest river in Australia, measuring from its source in northern New South Wales to its confluence with the Murray River at Wentworth, New South Wales. Including its longest contiguous tributaries it is long, making it the longest river system in Australia.The...
river system to the west are (or were) found naturally occurring in a number of coastal systems spanning almost the entire length of the range.
None of the river capture events that allowed native fish of the Murray-Darling system to cross into and colonise these East Coast river systems seem to have formed permanent linkages. The colonising Murray-Darling fish in these East Coast river systems have therefore become isolated from their parent species, and due to isolation, the founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
, genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
and natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
, have become separate species (see allopatric speciation
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration...
).
Examples include:
- Golden perchGolden perchThe golden perch, Macquaria ambigua, is an Australian native freshwater fish, primarily of the Murray-Darling river system. It is not a true perch of the genus Perca....
(Dawson-Fitzroy river system, central QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
). - Eel-tailed catfishEel-tailed CatfishThe eel-tailed catfish, Tandanus tandanus, is a species of catfish of the family Plotosidae. This fish is also known as dewfish, freshwater catfish, jewfish, and tandan.-Distribution:...
(several rivers, northern New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
) (However, note recent genetic research which now indicates eel-tailed catfish colonised east coast drainages in multiple colonisation events relatively recently (by evolutionary standards) and may subsequently have colonised the Murray-Darling system via an east-to-west river capture event, contrary to usual west-to-east capture events listed here.) - Macquarie perchMacquarie perchThe Macquarie perch is an Australian native freshwater fish of the Murray-Darling river system. It is a member of the Percichthyidae family and is closely related to the golden perch ....
(HawkesburyHawkesbury RiverThe Hawkesbury River, also known as Deerubbun, is one of the major rivers of the coastal region of New South Wales, Australia. The Hawkesbury River and its tributaries virtually encircle the metropolitan region of Sydney.-Geography:-Course:...
-NepeanNepean RiverThe Nepean River is a river in the coastal region of New South Wales, Australia.The headwaters of the Nepean River rise near Robertson, about 100 kilometres south of Sydney and about 15 kilometres from the coast. The river flows north in an unpopulated water catchment area into Nepean Dam, which...
rivers, Shoalhaven RiverShoalhaven RiverThe Shoalhaven River is a river rising from the Southern Tablelands and flowing into the ocean near Nowra on the South Coast of New South Wales, Australia.- History :...
, southern New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
). - River blackfishRiver BlackfishThe river blackfish, is an Australian native freshwater fish of the Murray-Darling river system, found from southern Queensland through to central Victoria. It is also found in some eastern and southern flowing coastal rivers...
(multiple rivers, VictoriaVictoria (Australia)Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
). - Murray codMurray CodThe Murray cod is a large Australian predatory freshwater fish of the Maccullochella genus and the Percichthyidae family. Although the species is a called cod in the vernacular, it is not related to the northern hemisphere marine cod species...
, whose eastern species/subspecies are:- Eastern freshwater codEastern freshwater codEastern freshwater cod, Maccullochella ikei, also known as eastern cod, are a large and striking predatory freshwater fish of the Maccullochella genus and the Percichthyidae family, that occur in the coastal Clarence River system of north-eastern New South Wales...
(Clarence RiverClarence River (New South Wales)The Clarence River is situated in northeastern New South Wales, Australia. The river originates on the watershed that marks the Queensland border. After flowing south and northeast for 394 km it then empties into the Pacific Ocean at Iluka/Yamba. On its journey it passes through the towns of...
system, northern New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
. It was also found in the Richmond RiverRichmond RiverThe Richmond River is a river in the north-eastern corner of New South Wales, Australia. It runs for approximately 170 km from the foothills of the Border Ranges past the towns of Kyogle, Casino, Coraki, Woodburn, where it turns northward and empties into the Pacific Ocean at Ballina. It has a...
system in New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
but that population is now extinct.) - Brisbane River codBrisbane River codThe Brisbane River cod was a unique form of Maccullochella cod that occurred naturally in the Brisbane River system, an east coast river system in south east Queensland, Australia...
(Brisbane RiverBrisbane RiverThe Brisbane River is the longest river in south east Queensland, Australia, and flows through the city of Brisbane, before emptying into Moreton Bay. John Oxley was the first European to explore the river who named it after the Governor of New South Wales, Thomas Brisbane in 1823...
system, southern QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
. That population is now extinct, and its exact taxonomic status is not known.) - The Mary River codMary River codMary River cod are a Maccullochella cod found in the coastal Mary River system of southern Queensland, Australia...
(Mary RiverMary River (Queensland)The Mary River is a river system in South East Queensland, Australia. The river rises at Booroobin in the Sunshine Coast hinterland, west of Landsborough...
, southern/central QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
.)
- Eastern freshwater cod
- The mountain galaxiasMountain galaxiasThe mountain galaxias species complex is a group of freshwater Galaxiid fish found all over southeast Australia. They form a cryptic species complex.-Classification:These fish were originally designated as a single species, Galaxias olidus, despite:...
species complexSpecies complexA species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
(multiple rivers, southern QueenslandQueenslandQueensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, New South WalesNew South WalesNew South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, VictoriaVictoria (Australia)Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
).
Olive perchlet (Ambassis agassizii), western carp gudgeon
Western Carp Gudgeon
The western carp gudgeon, Hypseleotris klunzingeri, is a carp gudgeon of the Eleotridae family. Carp gudgeons are small perciform fish found in the Australian Murray-Darling river system, mainly in lowland environments, but some have been observed in upland environments...
(Hypseleotris klungzingeri), pygmy perch (Nannoperca australis) and Australian smelt
Australian smelt
Australian smelt, Retropinna semoni, is a small, pelagic silvery freshwater fish found in large numbers in waters of the south eastern Australian mainland.-Distribution:Widely distributed through the south eastern part of the Australian mainland...
(Retropinna semoni) also appear to have made crossings into coastal systems, the last two species seemingly many times as they are found in most or all coastal streams in south eastern Australia as well as the Murray-Darling system.
Unfortunately, with the exception of eastern freshwater cod
Eastern freshwater cod
Eastern freshwater cod, Maccullochella ikei, also known as eastern cod, are a large and striking predatory freshwater fish of the Maccullochella genus and the Percichthyidae family, that occur in the coastal Clarence River system of north-eastern New South Wales...
and Mary River cod
Mary River cod
Mary River cod are a Maccullochella cod found in the coastal Mary River system of southern Queensland, Australia...
, it has not been widely recognised that these coastal populations of Murray-Darling native fish are separate species and their classifications have not been updated to reflect this. Many are threatened and two, the Richmond River cod
Richmond River cod
The Richmond River cod was a form of Maccullochella cod, now believed to have been eastern freshwater cod, Maccullochella ikei, that occurred naturally in the Richmond River system, an east coast river system in north-east New South Wales, Australia....
and the Brisbane River cod
Brisbane River cod
The Brisbane River cod was a unique form of Maccullochella cod that occurred naturally in the Brisbane River system, an east coast river system in south east Queensland, Australia...
, have become extinct.