Robert Mugabe

View of the Nile River, from a cruiseboat, between Luxor and Aswan in Egypt.

This is a list of the longest rivers on Earth. It includes river systems over 1,000 kilometers.

[edit] Definition of length

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The length of a river is very hard to calculate. It depends on the identification of the source, the identification of the mouth, and the scale of measurement of the river length between source and mouth. As a result, the length measurements of many rivers are only approximations. In particular, there has long been disagreement as to whether the Amazon or the Nile is the world's longest river.

The source of a river is not hard to determine because a river typically has many tributaries. Among the many sources, the one that is farthest away from the mouth is considered as the source of the river, thus giving a maximal river length. In practice, the tributary with the farthest source is not always the one given the name of the river. For example, the farthest source of the Mississippi River system is the source of the Jefferson River, a tributary of the Missouri River which in turn is a tributary of the Mississippi. However, a different (and shorter) tributary is identified as the Mississippi. When the river is measured from mouth to farthest source, it is called the Mississippi-Missouri-Jefferson. Also, it is hard to state exactly where a river begins as very often rivers are formed by seasonal streams, swamps, or changing lakes. In this article, length means the length of the longest continuous river channel in a given river system, regardless of name.

The mouth of a river is hard to determine in cases where the river has a large estuary that gradually widens and opens into the ocean; examples are the River Plate and the Saint Lawrence River. Some rivers like the Okavango or Colorado do not have a mouth; instead they dwindle to very low water volume and eventually evaporate, or sink into an aquifer, or get diverted for agriculture. The exact point where these rivers end will vary seasonally.

The length of a river between source and mouth may be hard to determine due to issues of map scale. Small scale maps (those showing large areas) tend to generalize, or "smooth" lines more than large scale maps (those showing small areas). According to the generally accepted ideal, length measurements should be based on maps that are of a large enough scale to show the width of the river, and the path measured is the path a small boat would take down the middle of the river.

Even when detailed maps are available, the length measurement is not always clear. A river may have multiple channels, or anabranchs. The length may depend on whether the center or the edge of the river is measured. It may not be clear how to measure the length through a lake. Seasonal and annual changes may alter both rivers and lakes. Other factors that can change the length of a river include cycles of erosion and flooding, dams, levees, and channelization. In addition, the length of meandering can change significantly over time due to natural or artificial cutoffs, when a new channel cuts across a narrow strip of land, bypassing a large river bend. For example, due to 18 cutoffs created between 1766 and 1885 the length of the Mississippi River from Cairo, Illinois, to New Orleans, Louisiana, was reduced by 218 miles (351 km).^[1]

These points make it difficult, if not impossible, to get an accurate measurement of the length of a river. The varying accuracy and precision also makes it difficult to make length comparisons between different rivers without a degree of uncertainty.

[edit] List of rivers longer than 1000 km

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One should take the aforementioned discussion into account when using the data in the following table. For most rivers, different sources provide conflicting information on the length of a river system. The information in different sources is between parentheses.

[edit] Notes

• When the length of a river is followed by an asterisk , it is an average of multiple information sources. If the difference in lengths between given information sources is significant, all lengths are listed. Likewise, if the lengths from secondary information sources are similar, they are averaged and that figure has an asterisk.
• Scientists debate whether the Amazon or the Nile is the longest river in the world. Traditionally, the Nile has been considered longer, but recent information indicates that the Amazon may be longer. Differences in the recorded length of the Amazon mainly depend on whether or not it is valid to take a course south of the Ilha de Marajó at the Amazon's mouth. New evidence, (dated 16 June 2007) obtained from a high-altitude scientific venture in the Andes, claims that "the Amazon is longer than the Nile by 100km, with its longest headwater being the Carhuasanta stream originating in the south of Peru on the Nevado Mismi mountain's northern slopes and flowing into the Río Apurímac"^[6]. However, the origin of the river at Nevado Mismi had already been known more than one decade earlier (see Jacek Palkiewicz), and satellite based measuring from this origin to the Amazon mouth has resulted in not more than 6,400 km.
• Generally, the most commonly used/anglicised name of the river is used. The name in a native language or alternate spelling may be shown.
• The exact percentage of each river in countries may be disputed (including the effects of political frontier disputes) or unknown.

The Mississippi River just north of St. Louis.

Saint Lawrence River along the New York-Quebec border.

[edit] River systems that may have existed in the past

[edit] Amazon-Congo

The Amazon basin formerly drained westwards into the Pacific Ocean, until the Andes rose and reversed the drainage.^[7]

The Congo basin is completely surrounded by high land, except for its long narrow exit valley past Kinshasa, including waterfalls around Manyanga. That gives the impression that most of the Congo basin was formerly on a much higher land level and that it was rejuvenated by much of its lower course being removed.

In Permian and early Triassic times Africa and South America were close against each other with no sea between (see continental drift and plate tectonics), and the Congo probably drained into the Amazon basin and eventually into the Pacific. Including part of its course that was completely lost when the South Atlantic opened, its total course may have been anything up to approximately 12,000 km (7,500 miles) long.

[edit] West Siberian Glacial Lake drainage

This river would have been about 10,000 km (6,000 miles) long, in the last Ice Age. See West Siberian Glacial Lake. Its longest headwater was the Selenga river of Mongolia: it drained through ice-dammed lakes and the Aral Sea and the Caspian Sea to the Black Sea.

[edit] Nile

Formerly Lake Tanganyika drained northwards into the Albert Nile, making the Nile somewhere around 700 miles longer, until in the Miocene the Virunga Volcanoes arose and blocked its course. Also, when the Mediterranean Sea was dry during the Messinian Salinity Crisis, the Nile extended northwards over the dry seabed and thus may have gained 100 miles or more in length.

[edit] Eridanos

The Eridanos was a large river during the Baventian Stage about two million years ago in the late early Pleistocene, when it was about 2700 kilometres or about 1700 miles long, a little shorter than the modern Danube. It began in Lapland, and then flowed through the area of the modern-day Gulf of Bothnia and Baltic Sea to western Europe, where it had an immense delta which spanned almost all the current North Sea. It was comparable in size to the current-day Amazon River.

[edit] Po

Similarly to the Nile, during the Messinian Salinity Crisis, the Po would have extended its course south-eastwards in what is today the seabed of the Adriatic Sea, more or less doubling its current length (652 km), likely varying seasonally according to how far it managed to flow across the hot dry seabed until it dried.

[edit] See also

• D River, Roe River, and Reprua River, all three of which are claimed to be the world's shortest river.
• Lake
• Ocean
• River
• Waterway
• List of drainage basins by area
• List of rivers by average discharge

[edit] References

[edit] Notes