The Earth’s Largest Rivers

The world’s largest rivers by discharge volume, drainage area, and length

When it comes to geographical extremes, one of the most common questions posed by children and adults alike is “what is the largest river in the world?” The word “largest,” however is an ambiguous term when it comes to rivers and many other natural features. Does largest mean the longest river, the one that has the largest drainage basin, or the river that discharges the most water? While we could simply rank the world’s rivers according to these three measurements and leave it at that, we felt that the relative sizes of the rivers could be best interpreted using infographics. Here we rank the 15 largest rivers in the world by length, drainage area, and discharge volume.

The Amazon River system is the largest in the world in terms of discharge, drainage area, and overall length.

A river’s discharge volume refers to the amount of water (usually measured in cubic meters or kilometers) that flows out of a river into another water body in a given amount of time. As you can see from the figure below, the Amazon river is by far the largest river in terms of discharge volume. In one second, the Amazon River discharges on average 175,000 cubic meters of water into the Atlantic Ocean. This is more water discharged per second than the next four largest rivers combined.

The Amazon River discharges so much water primarily because 1) it’s drainage basin covers the largest area of any river on Earth (see below), and 2) it is located in the world’s largest remaining tropical rainforest, which receives on average 108 inches of rain each year, or about 270 centimeters!  Note that the Congo is also located in an area of tropical rainforest, but it does not cover as much area. Other rivers, like the Yangtze and Mississippi, may be nearly as long as the Amazon, but they have smaller drainage basins and are found in more temperate climates that receive less rainfall.

World’s 15 largest rivers by water discharged. The size of the squares represent the volume discharged.

World’s Largest Rivers by Drainage Area

All rivers and streams have a drainage basin, also known as a watershed or catchment basin. Drainage basins are the area of land surrounding a water body that collects, or catches, precipitation and funnels the water, either on the surface or under the ground, to that water body. Typically, the larger a river’s drainage basin, the more water it will carry, and the greater its discharge volume will be.  Thus, drainage area and discharge volume are often related. However, some rivers are located in arid climates that receive very little rainfall, while others are in tropical regions that receive a lot of rainfall.

The Amazon River is once again ranked number one for having the largest drainage basin in the world, some 6.9 million square kilometers. This area covers a vast portion of the Amazon Rainforest, which receives a great deal of rainfall. As discussed above, the combination of a vast drainage basin and a wet, tropical climate, makes the Amazon River stand out from the rest..

The world’s 15 largest rivers ranked by drainage area. The size of the squares represent the area of each river’s drainage basin.

World’s Longest Rivers

Measuring river length is not quite as straight forward. Which river is the longest depends a great deal on how you measure it. At some point, as you trace the course of a river from the mouth to the headwaters you’ll have to decide which tributary to follow. If measured all the way to the beginning of the longest tributary, then the Amazon is likely the world’s longest river at nearly 7,000 km long.  This is, however, sill a matter of some debate, so consider rivers very close in length here to be approximately equal. This includes the Amazon and Nile, Yangtze, and Mississippi, and the Yenisei, Yellow and Ob. There’s a rather significant difference in length between the Mississippi and Yenisei, and between the Ob and the Congo, however. Note that some rivers are part of the same “river system,” which means that they combine at some point prior to emptying into a body of water. An example would be the Mississippi-Missouri river system, which joins near St.Louis, Missouri and eventually empties into the Gulf of Mexico.  

The 15 largest rivers in the world by total length (km).
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