Rhine

), Surselva, Graubünden, Switzerland
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, source2 = Rein Posteriur/Hinterrhein
, source2_location = Paradies Glacier, Graubünden, Switzerland
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, source_confluence = Reichenau
, source_confluence_location = Tamins, Graubünden, Switzerland
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, mouth = North Sea
, mouth_location = Netherlands
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, basin_size =
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The Rhine ; french: Rhin ; nl, Rijn ; wa, Rén ; li, Rien; rm, label= Sursilvan, Rein, rm, label= Sutsilvan and Surmiran, Ragn, rm, label=Rumantsch Grischun, Vallader and Puter, Rain; it, Reno ; gsw, Rhi(n), including in Alsatian and Low Alemannic German; ksh, label= Ripuarian and Low Franconian, Rhing; la, Rhenus ; hu, Rajna . is one of the major European rivers. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps. It forms part of the Swiss-Liechtenstein, Swiss-Austrian, Swiss-German borders. After that the Rhine defines much of the Franco-German border, after which it flows in a mostly northerly direction through the German Rhineland. Finally in Germany the Rhine turns into a predominantly westerly direction and flows into the Netherlands where it eventually empties into the North Sea. It drains an area of 9,973 sq km and its name derives from the Celtic ''Rēnos''. There are also two German states named after the river, North Rhine-Westphalia and Rhineland-Palatinate.

It is the second-longest river in Central and Western Europe (after the Danube), at about , with an average discharge of about .

The Rhine and the Danube comprised much of the Roman Empire's northern inland boundary, and the Rhine has been a vital navigable waterway bringing trade and goods deep inland since those days.
The various castles and defenses built along it attest to its prominence as a waterway in the Holy Roman Empire.
Among the largest and most important cities on the Rhine are Cologne, Rotterdam, Düsseldorf, Duisburg, Strasbourg, Nijmegen, and Basel.

Name

The variants of the name of the Rhine in modern languages are all derived from the Gaulish name ', which was adapted in Roman-era geography (1st century BC) as Greek ('), Latin '.

The spelling with ''Rh-'' in English ''Rhine'' as well as in German ' and French ' is due to the influence of Greek orthography, while the vocalization ''-i-'' is due to the Proto-Germanic adoption of the Gaulish name as *'' Rīnaz'', via Old Frankish giving Old English ', Old High German ', early Middle Dutch (c. 1200) ' (then also spelled ' or ').

The modern German diphthong ' (also used in Romansh) ' is a Central German development of the early modern period, with the Alemannic name ' keeping the older vocalism. In Alemannic, the deletion of the ending ''-n'' in pausa is a recent development; the form ' is largely preserved in Lucernese dialects. ' in Ripuarian is diphthongized, as is ' in Palatine. While Spanish has adopted the Germanic vocalism ', Italian, Occitan, and Portuguese have retained the Latin '.

The Gaulish name ''Rēnos'' ( Proto-Celtic or pre-Celtic ''*Reinos'') belongs to a class of river names built from the PIE root ' "to move, flow, run", also found in other names such as the Reno in Italy.

The grammatical gender of the Celtic name (as well as of its Greek and Latin adaptation) is masculine, and the name remains masculine in German, Dutch, French, Spanish and Italian.
The Old English river name was variously inflected as masculine or feminine; and its Old Icelandic adoption was inflected as feminine.

Geography

The length of the Rhine is conventionally measured in "Rhine-kilometers" (''Rheinkilometer''), a scale introduced in 1939 which runs from the Old Rhine Bridge at Constance (0 km) to Hook of Holland (1036.20 km).

The river is significantly shortened from its natural course due to a number of canalization projects completed in the 19th and 20th century. The "total length of the Rhine", to the inclusion of Lake Constance and the Alpine Rhine is more difficult to measure objectively; it was cited as by the Dutch Rijkswaterstaat in 2010.

Its course is conventionally divided as follows:

Headwaters and sources

Sources

The Rhine carries its name without distinctive accessories only from the confluence of the Rein Anteriur/Vorderrhein and Rein Posteriur/Hinterrhein next to Reichenau in Tamins. Above this point is the extensive catchment of the headwaters of the Rhine. It belongs almost exclusively to the Swiss canton of Graubünden, ranging from Saint-Gotthard Massif in the west via one valley lying in Ticino and Italy in the south to the Flüela Pass in the east. The Rhine is one of the four major rivers taking their source in the Gotthard region, along with the Ticino, Rhône and Reuss.

Traditionally, Lake Toma near the Oberalp Pass in the Gotthard region is seen as the source of the Anterior Rhine and the Rhine as a whole. The Posterior Rhine rises in the Rheinwald below the Rheinwaldhorn.

Anterior Rhine and Posterior Rhine

The source of the river is generally considered north of '' Lai da Tuma/Tomasee'' on ''Rein Anteriur/Vorderrhein'', although its southern tributary '' Rein da Medel'' is actually longer before its confluence with the Anterior Rhine near Disentis.

:The Anterior Rhine ( rm, Rein Anteriur, german: Vorderrhein) springs from ''Lai da Tuma/Tomasee'', near the Oberalp Pass and passes the impressive '' Ruinaulta'' formed by the largest visible rock slide in the alps, the Flims Rockslide.

:The Posterior Rhine ( rm, Rein Posteriur, german: Hinterrhein) starts from the Paradies Glacier, near the ''Rheinwaldhorn''. One of its tributaries, the ''Reno di Lei'', drains the '' Valle di Lei'' on politically Italian territory. After three main valleys separated by the two gorges, '' Roflaschlucht'' and ''Viamala'', it reaches Reichenau in Tamins.

The Anterior Rhine arises from numerous source streams in the upper Surselva and flows in an easterly direction. One source is '' Lai da Tuma'' () with the ''Rein da Tuma'', which is usually indicated as source of the Rhine, flowing through it.

Into it flow tributaries from the south, some longer, some equal in length, such as the ''Rein da Medel'', the ''Rein da Maighels'', and the '' Rein da Curnera''. The Cadlimo Valley in the canton of Ticino is drained by the ''Reno di Medel'', which crosses the geomorphologic Alpine main ridge from the south. All streams in the source area are partially, sometimes completely, captured and sent to storage reservoirs for the local hydro-electric power plants.

The culminating point of the Anterior Rhine's drainage basin is the Piz Russein of the Tödi massif of the Glarus Alps at above sea level. It starts with the creek ''Aua da Russein'' (lit.: "Water of the Russein").

In its lower course, the Anterior Rhine flows through a gorge named '' Ruinaulta'' (Flims Rockslide). The whole stretch of the Anterior Rhine to the Alpine Rhine confluence next to Reichenau in Tamins is accompanied by a long-distance hiking trail called ''Senda Sursilvana''.

The Posterior Rhine flows first east-northeast, then north. It flows through the three valleys named Rheinwald, Schams and Domleschg- Heinzenberg. The valleys are separated by the Rofla Gorge and Viamala Gorge. Its sources are located in the Adula Alps ( Rheinwaldhorn, Rheinquellhorn, and Güferhorn).

The Avers Rhine joins from the south. One of its headwaters, the ''Reno di Lei'' (stowed in the Lago di Lei), is partially located in Italy.

Near Sils the Posterior Rhine is joined by the Albula, from the east, from the Albula Pass region. The Albula draws its water mainly from the Landwasser with the Dischmabach as the largest source stream, but almost as much from the Gelgia, which comes down from the Julier Pass.

Numerous larger and smaller tributary rivers bear the name of the ''Rhine'' or equivalent in various Romansh idioms like ''Rein'' or ''Ragn''. Examples:
* Anterior Rhine area: ''Rein Anteriur/Vorderrhein'', '' Rein da Medel'', ''Rein da Tuma'', '' Rein da Curnera'', ''Rein da Maighels'', ''Rein da Cristallina'', ''Rein da Nalps'', ''Rein da Plattas'', ''Rein da Sumvitg'', ''Rein da Vigliuts'', '' Valser Rhine''
* Posterior Rhine basin: ''Rein Posteriur/Hinterrhein'', '' Reno di Lei'', ''Madrischer Rhein'', '' Avers Rhine'', ''Jufer Rhein''
* Albula-Landwasser area: In the Dischma valley, near Davos, far east of the Rhine, there's a place called ''Am Rin'' ("Upon Rhine"). A tributary of the Dischma is called ''Riner Tälli''. Nearby, on the other side of the Sertig, is the ''Rinerhorn''.

Alpine Rhine

Next to Reichenau in Tamins the Anterior Rhine and the Posterior Rhine join and form the Alpine Rhine. The river makes a distinctive turn to the north near Chur. This section is nearly 86 km long, and descends from a height of 599 meters to 396 meters. It flows through a wide glacial Alpine valley known as the Rhine Valley (german: Rheintal). Near Sargans a natural dam, only a few meters high, prevents it from flowing into the open Seeztal valley and then through Lake Walen and Lake Zurich into the Aare. The Alpine Rhine begins in the westernmost part of the Swiss canton of Graubünden, and later forms the border between Switzerland to the west and Liechtenstein and later Austria to the east.

As an effect of human work, it empties into Lake Constance on Austrian territory and not on the border that follows its old natural river bed.

The mouth of the Rhine into Lake Constance forms an inland delta. The delta is delimited in the west by the '' Alter Rhein'' ("Old Rhine") and in the east by a modern canalized section. Most of the delta is a nature reserve and bird sanctuary. It includes the Austrian towns of Gaißau, Höchst and Fußach. The natural Rhine originally branched into at least two arms and formed small islands by precipitating sediments. In the local Alemannic dialect, the singular is pronounced "Isel" and this is also the local pronunciation of ''Esel'' (" Donkey"). Many local fields have an official name containing this element.

A regulation of the Rhine was called for, with an upper canal near Diepoldsau and a lower canal at Fußach, in order to counteract the constant flooding and strong sedimentation in the western Rhine Delta. The Dornbirner Ach had to be diverted, too, and it now flows parallel to the canalized Rhine into the lake. Its water has a darker color than the Rhine; the latter's lighter suspended load comes from higher up the mountains. It is expected that the continuous input of sediment into the lake will silt up the lake. This has already happened to the former Lake Tuggenersee.

The cut-off Old Rhine at first formed a swamp landscape. Later an artificial ditch of about two km was dug. It was made navigable to the Swiss town of Rheineck.

Lake Constance

Lake Constance consists of three bodies of water: the Obersee ("upper lake"), the Untersee ("lower lake"), and a connecting stretch of the Rhine, called the Seerhein ("Lake Rhine"). The lake is situated in Germany, Switzerland and Austria near the Alps. Specifically, its shorelines lie in the German states of Bavaria and Baden-Württemberg, the Austrian state of Vorarlberg, and the Swiss cantons of Thurgau and St. Gallen. The Rhine flows into it from the south following the Swiss-Austrian border. It is located at approximately .

Obersee

The flow of cold, grey mountain water continues for some distance into the lake. The cold water flows near the surface and at first doesn't mix with the warmer, green waters of Upper Lake. But then, at the so-called ''Rheinbrech'', the Rhine water abruptly falls into the depths because of the greater density of cold water. The flow reappears on the surface at the northern (German) shore of the lake, off the island of Lindau. The water then follows the northern shore until Hagnau am Bodensee. A small fraction of the flow is diverted off the island of Mainau into Lake Überlingen. Most of the water flows via the ''Constance hopper'' into the ''Rheinrinne'' ("Rhine Gutter") and Seerhein. Depending on the water level, this flow of the Rhine water is clearly visible along the entire length of the lake.

The Rhine carries very large amounts of debris into the lake. In the mouth region, it is therefore necessary to permanently remove gravel by dredging. The large sediment loads are partly due to the extensive land improvements upstream.

Three countries border the Obersee, namely Switzerland in the south, Austria in the southeast and the German states of Bavaria in the northeast and Baden-Württemberg in the north and northwest.

Seerhein

The Seerhein is only long. It connects the Obersee with the 30 cm lower Untersee. Distance markers along the Rhine measure the distance from the bridge in the old city center of Constance.

For most of its length, the Seerhein forms the border between Germany and Switzerland. The exception is the old city center of Constance, on the Swiss side of the river.

The Seerhein emerged in the last thousands of years, when erosion caused the lake level to be lowered by about 10 meters. Previously, the two lakes formed a single lake, as the name still suggests.

Untersee

Like in the Obersee, the flow the Rhine can be traced in the Untersee. Here, too, the river water is hardly mixed with the lake water. The northern parts of the Untersee (Lake Zell and Gnadensee) remain virtually unaffected by the flow. The river traverses the southern, which, in isolation, is sometimes called ''Rhinesee'' ("Lake Rhine").

The Radolfzeller Aach adds large amounts of water from the Danube system to the Untersee.

Reichenau Island was formed at the same time as the Seerhein, when the water level fell to its current level.

Lake Untersee is part of the border between Switzerland and Germany, with Germany on the north bank and Switzerland on the south, except both sides are Swiss in Stein am Rhein, where the High Rhine flows out of the lake.

High Rhine

The Rhine emerges from Lake Constance, flows generally westward, as the ''Hochrhein'', passes the Rhine Falls, and is joined by its major tributary, the Aare. The Aare more than doubles the Rhine's water discharge, to an average of nearly , and provides more than a fifth of the discharge at the Dutch border. The Aare also contains the waters from the summit of Finsteraarhorn, the highest point of the Rhine basin. The Rhine roughly forms the German-Swiss border from Lake Constance with the exceptions of the canton of Schaffhausen and parts of the cantons of Zürich and Basel-Stadt, until it turns north at the so-called Rhine knee at Basel, leaving Switzerland.

The High Rhine begins in Stein am Rhein at the western end of the Untersee. Unlike the Alpine Rhine and Upper Rhine, it flows to the west. It descends from 395 m to 252 m.

Some stretches of the High Rhine between Stein am Rhein and Eglisau form the border between Switzerland on the south bank and Germany in the north. On other stretches, both sides are Swiss; in fact most of the canton of Schaffhausen is on the north bank. Between Eglisau and Basel, the High Rhine consistently forms the border.

The Rhine Falls are situated below Schaffhausen. With an average water flow of 373 m³/s (mean summer discharge 700 m³/s) it is the largest waterfall in Europe in terms of potential energy.

The High Rhine is characterized by numerous dams. On the few remaining natural sections, there are still several rapids.

Near Koblenz in the canton of Aargau, the Aare joins the Rhine. With an average discharge of 557 m³/s, the Aare is more voluminous than the Rhine, which has an average discharge of 439 m³/s. Nevertheless, the Alpine Rhine is considered the main branch, because it is longer.

Upper Rhine

In the center of Basel, the first major city in the course of the stream, is located the " Rhine knee"; this is a major bend, where the overall direction of the Rhine changes from west to north. Here the High Rhine ends. Legally, the Central Bridge is the boundary between High and Upper Rhine. The river now flows north as Upper Rhine through the Upper Rhine Plain, which is about 300 km long and up to 40 km wide. The most important tributaries in this area are the Ill below of Strasbourg, the Neckar in Mannheim and the Main across from Mainz. In Mainz, the Rhine leaves the Upper Rhine Valley and flows through the Mainz Basin.

The southern half of the Upper Rhine forms the border between France ( Alsace) and Germany (Baden-Württemberg). The northern part forms the border between the German states of Rhineland-Palatinate in the west on the one hand, and Baden-Württemberg and Hesse on the other hand, in the east and north. A curiosity of this border line is that the parts of the city of Mainz on the right bank of the Rhine were given to Hesse by the occupying forces in 1945.

The Upper Rhine was a significant cultural landscape in Central Europe already in antiquity and during the Middle Ages. Today, the Upper Rhine area hosts many important manufacturing and service industries, particularly in the centers Basel, Strasbourg and Mannheim-Ludwigshafen. Strasbourg is the seat of the European Parliament, and so one of the three European capitals is located on the Upper Rhine.

The Upper Rhine region was changed significantly by a Rhine straightening program in the 19th century. The rate of flow was increased and the ground water level fell significantly. Dead branches were removed by construction workers and the area around the river was made more habitable for humans on flood plains as the rate of flooding decreased sharply. On the French side, the Grand Canal d'Alsace was dug, which carries a significant part of the river water, and all of the traffic. In some places, there are large compensation pools, for example, the huge ''Bassin de compensation de Plobsheim'' in Alsace.

The Upper Rhine has undergone significant human change since the 19th century. While it was slightly modified during the Roman occupation, it was not until the emergence of engineers such as Johann Gottfried Tulla that significant modernization efforts changed the shape of the river. Earlier work under Frederick the Great surrounded efforts to ease shipping and construct dams to serve coal transportation. Tulla is considered to have domesticated the Upper Rhine, a domestication that served goals such as reducing stagnant bogs that fostered waterborne diseases, making regions more habitable for human settlement, and reduce high frequency of floods. Not long before Tulla went to work on widening and straightening the river, heavy floods caused significant loss of life. Four diplomatic treaties were signed among German state governments and French regions dealing with the changes proposed along the Rhine, one was "the Treaty for the Rectification of the Rhine flow from Neuberg to Dettenheim"(1817), which surrounded states such as Bourbon France and the Bavarian Palatinate. Loops, oxbows, branches and islands were removed along the Upper Rhine so that there would be uniformity to the river. The engineering of the Rhine was not without protest, farmers and fishermen had grave concerns about valuable fishing areas and farmland being lost. While some areas lost ground, other areas saw swamps and bogs be drained and turned into arable land. Johann Tulla had the goal of shortening and straightening the Upper Rhine. Early engineering projects the Upper Rhine also had issues, with Tulla's project at one part of the river creating rapids, after the Rhine cut down from erosion to sheer rock. Engineering along the Rhine eased flooding and made transportation along the river less cumbersome. These state projects were part of the advanced and technical progress going on in the country alongside the industrial revolution. For the German state, making the river more predictable was to ensure development projects could easily commence.

The section of the Upper Rhine downstream from Mainz is also known as the "Island Rhine". Here a number of river islands occur, locally known as "Rheinauen".

Middle Rhine

The Rhine is the longest river in Germany. It is here that the Rhine encounters some more of its main tributaries, such as the Neckar, the Main and, later, the Moselle, which contributes an average discharge of more than . Northeastern France drains to the Rhine via the Moselle; smaller rivers drain the Vosges and Jura Mountains uplands. Most of Luxembourg and a very small part of Belgium also drain to the Rhine via the Moselle. As it approaches the Dutch border, the Rhine has an annual mean discharge of and an average width of .

Between Bingen am Rhein and Bonn, the Middle Rhine flows through the Rhine Gorge, a formation which was created by erosion. The rate of erosion equaled the uplift in the region, such that the river was left at about its original level while the surrounding lands raised. The gorge is quite deep and is the stretch of the river which is known for its many castles and vineyards. It is a UNESCO World Heritage Site (2002) and known as "the Romantic Rhine", with more than 40 castles and fortresses from the Middle Ages and many quaint and lovely country villages.

The Mainz Basin ends in Bingen am Rhein; the Rhine continues as "Middle Rhine" into the Rhine Gorge in the Rhenish Slate Mountains. In this sections the river falls from 77.4 m above sea level to 50.4 m. On the left, is located the mountain ranges of Hunsrück and Eifel, on the right Taunus and Westerwald. According to geologists, the characteristic narrow valley form was created by erosion by the river while the surrounding landscape was lifted (see water gap).

Major tributaries in this section are the Lahn and the Moselle. They join the Rhine near Koblenz, for the right and left respectively. Almost the entire length of the Middle Rhine runs in the German state of Rhineland-Palatinate.

The dominant economic sectors in the Middle Rhine area are viniculture and tourism. The Rhine Gorge between Rüdesheim am Rhein and Koblenz is listed as a UNESCO World Heritage Site. Near Sankt Goarshausen, the Rhine flows around the famous rock Lorelei. With its outstanding architectural monuments, the slopes full of vines, settlements crowded on the narrow river banks and scores of castles lined up along the top of the steep slopes, the Middle Rhine Valley can be considered the epitome of the Rhine romanticism.

Lower Rhine

In Bonn, where the Sieg flows into the Rhine, the Rhine enters the North German Plain and turns into the Lower Rhine. The Lower Rhine falls from 50 m to 12 m. The main tributaries on this stretch are the Ruhr and the Lippe. Like the Upper Rhine, the Lower Rhine used to meander until engineering created a solid river bed. Because the levees are some distance from the river, at high tide the Lower Rhine has more room for widening than the Upper Rhine.

The Lower Rhine flows through North Rhine-Westphalia. Its banks are usually heavily populated and industrialized, in particular the agglomerations Cologne, Düsseldorf and Ruhr area. Here the Rhine flows through the largest conurbation in Germany, the Rhine-Ruhr region. One of the most important cities in this region is Duisburg with the largest river port in Europe (Duisport). The region downstream of Duisburg is more agricultural. In Wesel, 30 km downstream of Duisburg, is located the western end of the second east–west shipping route, the Wesel-Datteln Canal, which runs parallel to the Lippe. Between Emmerich and Cleves the Emmerich Rhine Bridge, the longest suspension bridge in Germany, crosses the river. Near Krefeld, the river crosses the Uerdingen line, the line which separates the areas where Low German and High German are spoken.

Until the early 1980s, industry was a major source of water pollution. Although many plants and factories can be found along the Rhine up into Switzerland, it is along the Lower Rhine that the bulk of them are concentrated, as the river passes the major cities of Cologne, Düsseldorf and Duisburg. Duisburg is the home of Europe's largest inland port and functions as a hub to the sea ports of Rotterdam, Antwerp and Amsterdam. The Ruhr, which joins the Rhine in Duisburg, is nowadays a clean river, thanks to a combination of stricter environmental controls, a transition from heavy industry to light industry and cleanup measures, such as the reforestation of Slag and brownfields. The Ruhr currently provides the region with drinking water. It contributes to the Rhine. Other rivers in the Ruhr Area, above all, the Emscher, still carry a considerable degree of pollution.

Delta

The Dutch name for Rhine is "Rijn". The Rhine turns west and enters the Netherlands, where, together with the rivers Meuse and Scheldt, it forms the extensive Rhine-Meuse-Scheldt delta, with the largest river delta in Europe. Crossing the border into the Netherlands at Spijk, close to Nijmegen and Arnhem, the Rhine is at its widest, although the river then splits into three main distributaries: the Waal, Nederrijn ("Nether Rhine") and IJssel.

From here, the situation becomes more complicated, as the Dutch name ''Rijn'' no longer coincides with the main flow of water. Two-thirds of the water flow volume of the Rhine flows farther west, through the Waal and then, via the Merwede and Nieuwe Merwede ( De Biesbosch), merging with the Meuse, through the Hollands Diep and Haringvliet estuaries, into the North Sea. The Beneden Merwede branches off, near Hardinxveld-Giessendam and continues as the Noord, to join the Lek, near the village of Kinderdijk, to form the Nieuwe Maas; then flows past Rotterdam and continues via Het Scheur and the Nieuwe Waterweg, to the North Sea. The Oude Maas branches off, near Dordrecht, farther down rejoining the Nieuwe Maas to form Het Scheur.

The other third of the water flows through the Pannerdens Kanaal and redistributes in the IJssel and Nederrijn. The IJssel branch carries one ninth of the water flow of the ''Rhine'' north into the IJsselmeer (a former bay), while the Nederrijn carries approximately two-ninths of the flow west along a route parallel to the Waal. However, at Wijk bij Duurstede, the Nederrijn changes its name and becomes the Lek. It flows farther west, to rejoin the Noord into the Nieuwe Maas and to the North Sea.

The name ''Rijn'', from here on, is used only for smaller streams farther to the north, which together formed the main river Rhine in Roman times. Though they retained the name, these streams no longer carry water from the Rhine, but are used for draining the surrounding land and polders. From Wijk bij Duurstede, the old north branch of the Rhine is called Kromme Rijn ("Bent Rhine") past Utrecht, first Leidse Rijn ("Rhine of Leiden") and then, Oude Rijn ("Old Rhine"). The latter flows west into a sluice at Katwijk, where its waters can be discharged into the North Sea. This branch once formed the line along which the Limes Germanicus were built. During periods of lower sea levels within the various ice ages, the Rhine took a left turn, creating the Channel River, the course of which now lies below the English Channel.

The Rhine-Meuse Delta, the most important natural region of the Netherlands begins near Millingen aan de Rijn, close to the Dutch-German border with the division of the Rhine into Waal and Nederrijn. The region between the Dutch-German border and Rotterdam, where the Waal, Lek, and Meuse run more or less parallel, is colloquially known as the "Great Rivers". Since the Rhine contributes most of the water, the shorter term ''Rhine Delta'' is commonly used. However, this name is also used for the river delta where the Rhine flows into Lake Constance, so it is clearer to call the larger one ''Rhine-Meuse delta'', or even '' Rhine–Meuse–Scheldt delta'', as the Scheldt ends in the same delta.

The shape of the Rhine delta is determined by two bifurcations: first, at Millingen aan de Rijn, the Rhine splits into Waal and Pannerdens Kanaal, which changes its name to Nederrijn at Angeren, and second near Arnhem, the IJssel branches off from the Nederrijn. This creates three main flows, two of which change names rather often. The largest and southern main branch begins as Waal and continues as Boven Merwede ("Upper Merwede"), Beneden Merwede ("Lower Merwede"), Noord ("the North"), Nieuwe Maas ("New Meuse"), Het Scheur ("the Rip") and Nieuwe Waterweg ("New Waterway"). The middle flow begins as Nederrijn, then changes into Lek, then joins the Noord, thereby forming Nieuwe Maas. The northern flow keeps the name IJssel until it flows into Lake IJsselmeer. Three more flows carry significant amounts of water: the Nieuwe Merwede ("New Merwede"), which branches off from the southern branch where it changes from Boven to Beneden Merwede; the Oude Maas ("Old Meuse"), which branches off from the southern branch where it changes from Beneden Merwede into Noord, and Dordtse Kil, which branches off from Oude Maas.

Before the St. Elizabeth's flood (1421), the Meuse flowed just south of today's line Merwede-Oude Maas to the North Sea and formed an archipelago-like estuary with Waal and Lek. This system of numerous bays, estuary-like extended rivers, many islands and constant changes of the coastline, is hard to imagine today. From 1421 to 1904, the Meuse and Waal merged further upstream at Gorinchem to form Merwede. For flood protection reasons, the Meuse was separated from the Waal through a lock and diverted into a new outlet called " Bergse Maas", then Amer and then flows into the former bay Hollands Diep.

The northwestern part of the estuary (around Hook of Holland), is still called ''Maasmond'' ("Meuse Mouth"), ignoring the fact that it now carries only water from the Rhine. This might explain the confusing naming of the various branches.

The hydrography of the current delta is characterized by the delta's main arms, disconnected arms ( Hollandse IJssel, Linge, Vecht, etc.) and smaller rivers and streams. Many rivers have been closed ("dammed") and now serve as drainage channels for the numerous polders. The construction of Delta Works changed the Delta in the second half of the 20th century fundamentally. Currently Rhine water runs into the sea, or into former marine bays now separated from the sea, in five places, namely at the mouths of the Nieuwe Merwede, Nieuwe Waterway (Nieuwe Maas), Dordtse Kil, Spui and IJssel.

The Rhine-Meuse Delta is a tidal delta, shaped not only by the sedimentation of the rivers, but also by tidal currents. This meant that high tide formed a serious risk because strong tidal currents could tear huge areas of land into the sea. Before the construction of the Delta Works, tidal influence was palpable up to Nijmegen, and even today, after the regulatory action of the Delta Works, the tide acts far inland. At the Waal, for example, the most landward tidal influence can be detected between Brakel and Zaltbommel.

Geologic history

Alpine orogeny

The Rhine flows from the Alps to the North Sea Basin. The geography and geology of its present-day watershed has been developing since the Alpine orogeny began.

In southern Europe, the stage was set in the Triassic Period of the Mesozoic Era, with the opening of the Tethys Ocean, between the Eurasian and African tectonic plates, between about 240  MBP and 220 MBP (million years before present). The present Mediterranean Sea descends from this somewhat larger Tethys sea. At about 180 MBP, in the Jurassic Period, the two plates reversed direction and began to compress the Tethys floor, causing it to be subducted under Eurasia and pushing up the edge of the latter plate in the Alpine Orogeny of the Oligocene and Miocene Periods. Several microplates were caught in the squeeze and rotated or were pushed laterally, generating the individual features of Mediterranean geography: Iberia pushed up the Pyrenees; Italy, the Alps, and Anatolia, moving west, the mountains of Greece and the islands. The compression and orogeny continue today, as shown by the ongoing raising of the mountains a small amount each year and the active volcanoes.

In northern Europe, the North Sea Basin had formed during the Triassic and Jurassic periods and continued to be a sediment receiving basin since. In between the zone of Alpine orogeny and North Sea Basin subsidence, highlands resulting from an earlier orogeny ( Variscan) remained, such as the Ardennes, Eifel and Vosges.

From the Eocene onward, the ongoing Alpine orogeny caused a north–south rift system to develop in this zone. The main elements of this rift are the Upper Rhine Graben, in southwest Germany and eastern France and the Lower Rhine Embayment, in northwest Germany and the southeastern Netherlands. By the time of the Miocene, a river system had developed in the Upper Rhine Graben, that continued northward and is considered the first Rhine river. At that time, it did not yet carry discharge from the Alps; instead, the watersheds of the Rhone and Danube drained the northern flanks of the Alps.

Stream capture

The watershed of the Rhine reaches into the Alps today, but it did not start out that way.Berendsen and Stouthamer (2001) In the Miocene period, the watershed of the Rhine reached south, only to the Eifel and Westerwald hills, about north of the Alps. The Rhine then had the Sieg as a tributary, but not yet the Moselle. The northern Alps were then drained by the Danube.

Through stream capture, the Rhine extended its watershed southward. By the Pliocene

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