Although the answer to the question “What is the longest river ?” might sound simple—find the source measurement, mouth, and source, but between these steps are many definitions, fractals and hydrology and, perhaps most important, national pride. The issue is so complex that several hydrologists contacted by Mental Floss said that river length isn’t considered a useful measurement anymore. What is the longest river anywhere in the world?

What length is a river?

According to Laurel Larsen, an associate professor in the University of Berkeley’s geography department, “The length of a particular river is the length that is the longest feasible along-thalweg continuous distance that can be traced from the headwaters (first order stream) to the mouth of a river.”

To break down the words, the thalweg is “the line that connects the lowest or deepest points along the bed of a valley or stream.” The first order streams are more complex. Strahler is the most popular method to categorize streams according to their order. It classifies streams that have no tributaries, or that is just beginning to flow into the river, as first order. Two streams of the first order join to form another stream. When two streams of second order connect to form the third order stream. But streams that cross with a stream belonging to the second order remains as a stream of second order.

The source of a river then is thought to be the furthest distance to the source of a stream with no inputs. However, in reality this is extremely difficult to identify. And it’s not an ideal system. (For reasons of historical significance the origin of the Mississippi is usually treated as distinct from the Missouri even though the traditional definition of them as a single river system.)

What’s with the mouth? This is also contentious. For certain rivers the mouths are easy to find. However, for larger rivers that enter the ocean, like the Amazon the location where the mouth is located could make a huge difference.

Do we intend to answer the question?

Typically, the Nile has been regarded as the longest river in the world one, with the Amazon being a close second. But in 2007, a team of Brazilian researchers announced that a new analysis put the Amazon at the top. They got this by identifying an entirely new source, and most importantly, a brand new mouth. The mouth of the Amazon was previously situated on the island’s north side. The new report shows that the river was now wrapped around the island’s south side, and then to the Para River, and then out to ocean.

While it may not be significant, Marajo Island is larger than Switzerland. The new source and the mouth that was built has a distance longer than the Nile.

The issue was controversial. Para River is often associated with the Tocantins River, not with the Amazon. Recent studies tend to confirm that the Para, while it contains certain Amazon water, is quite distinct from the Amazon. That means that the best bet for the longest river in the world is still the Nile.

But there’s another, more fundamental issue with measuring a river what does length actually refer to?

What’s the cause?

In the early 20th century, mathematician Lewis Fry Richardson made the observation that Spain and Portugal did not agree on the length of their borders. It was 987 km in Spain in comparison to Portugal claimed it was 1214 kilometers. The dispute wasn’t due to territorial disputes or any other such thing; Richardson explained that it was the length of the measuring stick. The measuring stick becomes smaller and is able to capture more of the intricate curves and the subtleties in bends.

The rivers are exactly the same. They meander, and they have tiny curves. You can zoom in even further to view more bends and turns within the thalweg.

It’s referred to as the coastline paradox. The length of anything complex is basically impossible to determine because the length keeps increasing the smaller the measurement goes.

In light of both these reasons and the inherent challenges of determining length, many researchers have told Mental Floss that river length isn’t really something that important, and what’s really important is drainage area, which is the area of land that provides the water flow to the river. This metric is much less complicated than river length since it requires only a few elevation measurements. According to Nature, the Amazon is the largest river with 6.3 million km of drainage. If it was a nation, the drainage basin would be the seventh largest nation in the world, just behind Australia. https://www.freejobalert.com/longest-rivers-in-the-world/994260/