Ranking of world's longest rivers

  1. Hi. Usually Nile river is assumed as world's longest river with its 4250 miles length but sometimes Mississippi River is assumed world's longest river. River Amazon is world second longest river with its 4000 miles length. So what should be the true ranking?
    Last edited: Jun 23, 2014
  2. jcsd
    Earth sciences news on Phys.org
  3. davenn

    davenn 3,381
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    4.25 miles isn't very long :wink:

    what does google have to say in references ?

  4. This is from Wikipedia: "The Nile (Arabic: النيل‎, Eg. en-Nīl, Std. an-Nīl; Coptic: ⲫⲓⲁⲣⲱ, P(h)iaro; Ancient Egyptian: Ḥ'pī and Iteru) is a major north-flowing river in northeastern Africa, generally regarded as the longest river in the world.[2] It is 6,853 km (4,258 miles) long. " And it is strange that it is generally regarded as the longest then Mississippi River should sometimes be regarded as the longest.
  5. jtbell

    Staff: Mentor

    Please give a specific source for this. Who says that the Mississippi is the world's longest river?
  6. Sorry, it seems it is wrong that Mississippi is the longest. But why does
    wikipedia say the Nile is generally longest?
  7. SteamKing

    SteamKing 8,311
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    Trying to fix a length to a river is difficult. Rivers can change the course of their flow over time. For some rivers, like the Amazon, parts of it may be poorly mapped, and the headwaters in the Andes Mountains may be poorly explored.

    Depending on the reference cited, the Mississippi-Missouri river may be No. 3 (http://www.infoplease.com/toptens/worldrivers.html) or No. 4 (http://en.wikipedia.org/wiki/List_of_rivers_by_length).

    There is still some doubt that the headwaters of the Nile have been reached for certain. The latest expedition to what was thought to be the source of the White Nile took place in 2010.

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  8. Volume of discharge seems more important than length. On that basis the Amazon wins outright. It is an order of magnitude greater than the number two river (Congo) and two orders of magnitude more than the Nile.

    See Wikipedia
  9. using wikipedia

    Wikipedia does not "say" anything. It references sources that say things. So - check the footnotes, which reference the Encyclopedia Britannica. When it does not reference sources, it is being non-encyclopedic, and the information should be treated with suspicion.

    Different pages on the wiki may be linked to different references which may say contradictory things.

  10. I want to learn where is starting point of Amur River but I can not do a good search. Can you help me with correct
    parameters for I can do it.
  11. HallsofIvy

    HallsofIvy 40,218
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    At some point in the early exploration of what is now the United States by people of European descent some one decided that the Missouri river ran into the Mississippi which then continued to the gulf of Mexico. It could as easily have been decided that the Mississippi ran into the Missouri which then continued to the gulf of Mexico. Had that been done, since the distance from the confluence to the head of the Missouri is greater than the distance from the confluence to the head of the Mississippi, the "Missouri", now including the distance from the confluence to the gulf of Mexico, would be the longest river in the world. Some texts will refer to the "Mississippi- Missouri complex", to mean just that, as the longest river.
  12. jtbell

    Staff: Mentor

    If you look at the Mississippi-Missouri confluence on Google Maps or Google Earth, it seems "obvious" that the Mississippi goes "straight through" and the Missouri "runs into" it.

    On the other hand, if you look at the Mississippi-Ohio confluence at Cairo IL, it seems equally obvious to me that the Ohio goes "straight through" to the lower Mississippi and the middle Mississippi "runs into" it. According to http://en.wikipedia.org/wiki/Mississippi_River the Ohio also carries a larger volume of water than the middle Mississippi.

    So there's some degree of historical arbitrariness in terminology.

    (Disclaimer: I grew up in Ohio, so I have a slight bias here. :wink:)
    Last edited: Jul 12, 2014
  13. SteamKing

    SteamKing 8,311
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    You didn't start your search with this article perhaps?

  14. Baluncore

    Baluncore 2,423
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    I think, if in order to compile a ranked or ordered list, you look at the statistics of rivers, you will need to specify some criteria for measurement.

    Does it matter what your criteria are if you do not specify why you need the ordered list?

    Strategies for assessment:

    1. Flow Rate. Follow a river from the sea, then always take the higher flow rate branch until you get to a damp spot that does not flow. What if the flow is seasonal, a river may be dry for several years before a rain event occurs.

    2. Branch Length. Map the river based on the distance between the nodes where streams meet. Search for the terminal node furthest from the estuary; by the shortest possible route?

    3. Total Area of the combined watershed. Water does not need to flow all the time.

    4. Nomenclature. If the name of the river changes then is it the same river? What if two different named rivers meet to form a third named river.

    Where does a river start? The headwaters will probably need to be defined as a spring or a wet spot where flow downstream is first visible on the surface. If scale is ignored then it will probably come down to the hopefully convergent limit of a fractal search between mineral grains in the soil.

    Can a river start at a lake? Probably not, many long rivers have deep sections that might be called lakes, so claiming a river starts at a lake is probably unreasonable. Water must somehow reach that lake.

    If water rises from a cave system, then what length of the unmapped cave system should be included as the river? Chemically tracing “disappearing streams” to their outlet may lead to an extension of another river by an unknown length.

    Where does a river end? Does the river end in the estuary where sea water meets the fresh water? At high or at low tide? During flood or drought?

    Luckily there are few long rivers that feed a salt basin without an outflow. In Australia, Coopers Creek flows into Lake Eyre. When the lake starts to fill, how much of Lake Eyre is actually counted as Coopers Creek?

    What about a delta, is it the shortest or the longest channel that should be considered? I believe the shortest should be measured as the longest will be flow variable.
    Which side of an anabranch or braided channel should you follow? Should it be the shortest, or the one that flows for the greater proportion of the time.

    When a river divides, say during high water, which channel should be measured? The Atchafalaya River significantly shortens the Mississippi during times of high water.
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  15. I thought Amazon is the largest ?
  16. Baluncore

    Baluncore 2,423
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    seoservices. Welcome to PF.
    Largest in total annual flow volume, length or watershed catchment area?
  17. The OP inquired about the longest, not the largest.
  18. dextercioby

    dextercioby 12,293
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    This is one of the hot topics in Geography. Yes, different sources give different data, even though we work with GPS and military satellites that can 'see' an apple from kilometers above.

    I think it's fair to see this truly as controversial, henceforth we don't have the longest river in the world, but rivers: Amazon and Nile.
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