Then distances from Lago Junín to several potential source points in the uppermost Mantaro river were measured, which enabled them to determine that the Cordillera Rumi Cruz was the most distant source of water in the Mantaro basin (and therefore in the entire Amazon basin).
To find out where the water originated in the Mantaro River system, researchers measured distances from Lago Junín to various potential sources. This revealed that the Cordillera Rumi Cruz was the furthest upstream source of water in the Mantaro basin and by extension, the entire Amazon basin.