Correct placement of the most distant source of the Amazon River in the Mantaro River drainage

The Amazon River (Rio de las Amazonas') has the highest discharge of any river in the world and is also the longest or second longest. Its source has therefore intrigued scholars and explorers for centuries. A river's source is often defined as the most distant upstream point in the drainage basin. For the past several decades, the longest upstream extension of the Amazon River has been held to be the Nevado Mismi area of the Rio Apurimac drainage. We overturn this longstanding view by employing topographic maps, satellite imagery, digital hydrographic datasets and GPS tracking data to show that the Cordillera Rumi Cruz (10.7320 degrees S, 76.6480 degrees W; elevation approximate to 5220m) in the Rio Mantaro drainage lies 75-92km further upstream than Nevado Mismi. We compare various methods for measuring each of the Rio Apurimac and Rio Mantaro lengths, and show that high-resolution satellite imagery and GPS tracking most closely follow the path of the water. Our results reposition the most distant source' of the Amazon to a more tropical location, change the uppermost approximate to 800km of river to this point, and add 75-92km to the river's maximal length.