On the Length Data of the World's Rivers over 5000 km in Length
Yang Liankang Centre of Qualified Personell , Ministry of Land and Resources
4 Hou Luoquan Hutong, Western District , Beijing , 100035, China.
Pan Yuntang Graduate School , Chinese Academy of Sciences
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Abstract
As river is mother of mankind , the longer rivers bear particularly large influence on mankind . However , up to now., the international geographical circle can not provide a satisfactory length data of the longer rivers in the world . According to the on-the-spot investigation for 44 years and the analysis of more than 100 items of data source , the authors of the present paper have suggested a classification standard of the rivers¡¯ length in order of 5000km , 4000km, 3000km , 2000km,1000km and < 1000km. Thereare 7 rivers in the world , i . e. , Amazon River ( ? , 6275- 7025 km ) , Nile River ( 6671km ) , Mississippi River (6415 km) , Yangtze River ( 6300 km) , Yellow River (5501km) , Ob River (5410km) and Yenisei River (5075 km) . The longitudinal profiles of these rivers are showed in the figure . However , the precise data of their lengths have yet to be further verified . |
___ Separate accounts ___
As a result of repeated measurement , the length data of the Yangtze River and the Yellow River had remarkable changes from 1950s to 1960s and 1970s . Having made the on- foot investigation to these two rivers for 1111 days , the authors consider that the recently published length data obtained from the calculation by segment are true and reliable . The farthest source of the Yellow River _ Lalangqingqi , discovered by the first author ,is 30. 5km further up the previously defined source .This discovery , with additional length in its mouth , has changed the length of the Yellow River from the previous 5464 km to the present figure ,being the one among the longest rivers with the length over 5500km .
The length data of the Ob River and the Yenisei River are based upon the¡±
Great Encyclopedia of Soviet Union¡± and the local materials acquired by the authors in the on-the-spot investigation . These materials are very important ,however it has not been quoted and verified .As early as in the 1930s , the Nile River had the length data obtained for every segment below the Victoria Lake . Afterward the length data obtained from the source to the Victoria Lake are comparatively stable.
The recommendation of the Mississippi River Commission about the length data of the Mississippi River is very clear , and can be used for reference in the research of other rivers . However the length data of the Amazon River vary from 6275km to 7025 km , and is thus difficult to be put among other longer rivers in the world in its right order .
___Comparison___
By comparison , the author have found very large differences in the recognition of the length data of the rivers and in the measurement method of them .
Firstly , there are divergeces in the method and even the scale used in on_the_spot and on_the_map measurement .
Secondly, there are divergences in the recognition of the length :
1 , Source__ the Sources of the Yangtze River and the Amazon River are the glacial sources. Now the river length have been calculated from the end of the glacier .Actually ,the melted water of the glacier peak is also a part of the source . The river lengths of the other rivers were mostly calculated from the location of the water affluence . .Actually ,the water flow also exists between the watershed and the water affluence and should be added into the river lengths .
2 , Mouth__ the mouth of the river is better to be calculated to the¡°obstacle bar¡±
. In addition , many rivers are characterized by the outward extension year after year . Therefore , the comparison, of the river lengths must be carrind out according to the length data of the same year .3 , The main stream line or the median line__What is the standard for measuring the river length?
¡¡
____Expectation___
At present , the situation is very advantageous because the international geographical circle have standardized the length of the longer rivers . First . the united global remote_ sensing atlas has been published since the 1970s. Secondly , China and Russia have been opened successively ,so that it is favourable for the on _the_ spot correction.
Therefore , the authors suggest :
1 , carry out the on _the_ spot measurement on the basis of the 1: 100,000 global united remote_ sensing maps.
2 , list the different recognitions about the river source , river mouth and river length etc. Measure out correspondng data , and in the end , unite these recognitions .
Now , it is the key that we must urge the international geographical circle to look squarely to this situation and to pay close attention to consult with sovereign states and to organize the surveyors and the geomorphologists to make plans and to resolve the problem on the river length of the 7 longer rivers in the term of the earlest 10 year of the 21 century in order to promote the research on the river length in the world.
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