World's longest rivers: Which is No. 1?

Posted: July 02, 2007

When it comes to length, the Amazon River has always ranked No. 2 - slightly shorter than Africa's Nile, slightly longer than China's Yangtze.

Now scientists - not surprisingly from Brazil - say it's time to change the score.

According to that nation's Institute of Geography and Statistics, researchers have long known that the real source of the Amazon was not where people thought it was.

An expedition in 2000, followed by another this year, traced the Amazon's headwaters beyond their long-accepted source, the Marañón River. Aided by satellite navigation, explorers continued south, to a trickle in the Peruvian Andes.

This, plus refiguring the location of its mouth, added about 620 miles to the Amazon - edging out the Nile.

The research hasn't been "peer-reviewed," and most cartographers aren't changing their maps just yet. (Still in a state of de Nile?)

Either way, the winning number is little more than a whimsical bit of trivia to folks in the field.

"It's really kind of a technical game," says Mark Sabaj, fisheries collections manager at the Academy of Natural Sciences and a veteran of several Amazon expeditions.

Finding a river's headwaters is like picking among thousands of outer twigs for the right starting point to measure the length of a tree. Rivers have almost as many official lengths as there are scientists to calculate them.

Anyway, says Sabaj, the Amazon is clearly superlative by so many measures.

At its mouth, it pumps out four times as much water as the Nile. Its drainage area - more than two million square miles - is by far the largest on the planet. And an Amazon exhibit at the Academy boasts the river is the world's most biologically diverse.

- Sandy Bauers

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