The Amazon River (US Spanish and Portuguese: Amazonas) in South America is generally regarded as the second longest river in the world and is by far the largest by waterflow with an average discharge of about 209,000 metres per second (7,381,000 cu ft/s), greater than the next seven largest rivers combined (not including Madeira and Rio Negro, which are tributaries of the Amazon). The Amazon, which has the largest drainage basin in the world, about 7,050,000 square kilometres (2,720,000 sq mi), accounts for approximately one-fifth of the world's total river flow. In fact, the river would have the biggest drainage basin in the world even just counting Brazil, which it enters with only 1/5 of the volume that will finally be discharged into the Atlantic.
In its upper stretches, above the confluence of the Rio Negro, the Amazon is called Solimões in Brazil; however, in Peru, Colombia and Ecuador, as well as the rest of the Spanish-speaking world, the river is generally called the Amazon downstream from the confluence of the Marañón and Ucayali rivers in Peru. The Ucayali-Apurímac river system is considered the main source of the Amazon, with its main headstream being the Carhuasanta glacial stream flowing off the Nevado Mismi mountain.
