Amazon River

node · earth · Amazon Basin

The largest river on Earth by discharge, delivering on average of the order of 200,000 cubic metres per second to the Atlantic - roughly a fifth of all fresh water reaching the ocean from rivers, and more than the next several largest rivers combined. Its length is genuinely contested rather than merely imprecise. Since a 1971 National Geographic expedition the accepted headwater has been the Carhuasanta stream on Nevado Mismi in southern Peru, in the Apurimac drainage, giving a length usually stated as about 6,400 km. A Brazilian survey published in 2007-2008 claimed a longer course and, with it, primacy over the Nile; a 2014 study by Contos and Tripcevich argued that the most distant source lies instead in the Mantaro drainage, adding a further stretch. No measurement has settled it, because the answer depends on which of several defensible source streams and which of several channels through the delta one chooses. Downstream the river carries Andean sediment: the Solimoes runs pale with it, while the Rio Negro drains ancient weathered shield rock and runs dark with dissolved humic acids.