Sunday, 18 December 2011

Amazonas - the World's Longest River?

It goes without saying that rivers have played an important part in the development of human civilisation.  In the age of air-travel, it's sometimes difficult to fathom the historical importance of rivers, whether as modes of transport or obstacles to colonisation.  Whilst researching for my partner blog Walking the Chesters, I was surprised to learn how much of an obstacle the River Severn was to the conquering Roman armies, as they tried to subdue Wales.

When I lived in Bangkok, I was impressed with the way that getting a boat down the Chao Praya is still used as a quick and easy method of travelling from one part of the city to another (certainly avoids all those traffic jams).  I know that some people use river transport on the Thames to get to work every day, but it's not really comparable, being the exception rather than the rule.  The Amazon is still a place where river transport is often the only logical option and I find that exciting, being so used to land- or air-based travel. 

Also, when I was blogging about Paraguay I learned that Paraguay is like a 'land-locked island', being surrounded on all sides by rivers, which made colonisation difficult for the conquistadors


Is the Amazon the longest river in the world?

Well, officially, the Amazon is the world's second-longest river, the longest river being the Nile.  It can be difficult to decide exactly how long a river is and the decision really depends on where you decide the mouth of the river is and where its true source lies.
The Nile by Michael Gwyther-Jones

How do you determine the 'true source' of a river?

The 'true source' of a river is understood to be the source of a river's tributary which is furthest away from the river's mouth.  Rivers tend to originate at high altitudes, as ice melts and flows downwards to the sea.  The world's longest rivers, including the Amazon and the Nile, have many tributaries which add volume to the rivers as they join them on their way to the open sea. 

Europeans have been interested in finding the source of the Nile since Greek and Roman times.  At various times in the past, the source of the Nile was believed to be in Ethiopia and even in places as far away as the Niger. The Victorians and their obsession with finding the answer to every question, were determined to locate the source of the Nile for once and for all. 

After the 'discovery' of Lake Victoria in 1858, there was a very famous public quarrel between the British explorers, Speke and Burton, as to which one of them had discovered the source of the Nile and whether the source was at Lake Victoria, or further south at Lake Tanganyika. Interestingly, the most remote source of the Nile is still undetermined in the 21st century, but believed to be at the Ruvyironza River in Burundi.

The Source of the Amazon

The 'most remote' source of the Amazon is believed to be at Nevado Mismi, in the south of Peru.  As part of my research for this blog, I watched Bruce Parry's fascinating TV series, Amazon.  Bruce started his journey at this 'official' source of the Amazon, on the Ucayali river.  Ed Stafford, the first person to walk the entire length of the Amazon (finishing in August last year), also started his journey at Nevado Mismi.  

The Amazon by CIFOR


Other major river sources

The source of China's longest river, the Yangtze, is believed to be at Geladaindong Peak in Qinghai province near the border with Tibet.  The Mississippi River is believed to start at Lake Itasca in Minnesota.  Russia's longest river, the Yenesei flows from its source at Mungaragiyn-Gol in Mongolia all the way to the Arctic ocean.  Western Europe's longest river, the Rhine is a real minnow, in world terms, being the 123rd longest river.  It has its source at the Tomasee in Switzerland.

The rivers of the Amazon

The thing that has suprised me most, on this learning journey, is that the Amazon is really a sum of its parts, rather than one single river.  Although I'd not heard of any of them before I started researching for this blog, I've come to realise that the Amazon's tributaries are magnificant rivers in their own right. 

I'm listing some of the main tributaries of the Amazon below.

First are the Negro and Branco, the black and white rivers. The Negro comes in from Columbia and is the world's largest 'blackwater' river, ie. a slow-flowing river that winds through forested wetlands and swamps.  The quality of the earth it flows through is incredibly poor and it's called Negro (black)because of the tannins that leach into the river, giving it a tea-stained colour.  In Bruce Parry's Amazon, there is an interesting shot of the Amazon/Negro confluence, where the dark waters of the Negro add a cloudy mix to the clearer waters of the Amazon.

The Japura also rises in Columbia and flows into the Solimoes, a river with several names, also called the Ica in Brazil and the Putumayo as it forms the border between Columbia and Peru.
The Napo river comes in from Ecuador and the Ucayali comes from the official source of the Amazon in Peru. The Juruá river also comes in from Peru, as does the Purus.  
People of the Amazon by CIFOR


The great Bolivian rivers such as the Beni and Mamoré join the river Madeira just after Porto Velho, where they flow on to meet the Amazon just east of Manaus. Porto Velho, the capital of Rondônia, was built to serve the needs of the Mamoré-Madeira railway.  An unsuccessful attempt to link Bolivia with the Amazon and ports of the Atlantic, the Mamoré-Madeira railway cost millions of dollars and thousands of lives to build.

The Madeira is the Amazon’s biggest and, arguably, most important tributary.  I've learned that the name madeira, also the name for the Atlantic archipelago, comes from the Portuguese word for ‘wooded’. The Madeira-Mamoré is pretty impressive, being only slightly shorter than the Volga, it's the world’s 19th longest river.

The Amazon’s eastern-most tributaries, the Tapajós, the Iriri and the Xingu all rise in Brazil. They mostly flow through Amazonas' neighbouring state, Pará.  They are the closest to ‘civilisation’ and, therefore, quite often the scene of mass deforestation and conflict between the indigenous people and the corporations that are keen to exploit the Amazon region's resources.  Currently, the most controversial project is the proposed construction of the Belo Monte Dam, which faces opposition by indigenous peoples such as the Kayapo of the Xingu river.

The Araguaia and Tocantins rivers aren’t really tributaries of the Amazon, but both flow into Atlantic at Ilha de Marajo, close to the mouth of the Amazon.


Aerial view of the Amazon by CIFOR
A sobering fact for someone from Western Europe is that, even the shortest of the Amazon tributaries that I've just mentioned - the Iriri - is still longer than the Rhine!

The Amazon-Congo river?

One interesting hypothesis is that the Amazon and Congo were once part of the same river system, which drained into (what is now) the Pacific ocean.  When the continental shelves divided, separating Africa from South America and after the Andes rose, it's posited that the Amazon changed direction to flow into (what is now) the Atlantic ocean.  If this hypothesis is true, then it means the Amazon-Congo was the longest river in history, at an estimated 7,500 miles (12,000 km).

Image credits:

The view of the River Nile is by flickr member Michael Gwyther-Jones who is an architect from Cardiff in Wales.  You can see more of Michael's photos on his photo stream.


The photos of the Amazon were posted on Flickr by the Center for International Forestry Research (CIFOR), a nonprofit, global facility dedicated to advancing human wellbeing, environmental conservation and equity.  They have a really interesting website where you can find out more about the work that they do. 

Thanks to Michael and CIFOR for sharing these images with us, using the Creative Commons license. 
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