Major Amazon tributary reaches record low as drought takes hold

A boat is stuck in the Rio Negro during a drought (Edmar Barros/AP)

One of the Amazon river’s largest tributaries has reached its lowest level since official measurements began 121 years ago.

The level of the Rio Negro at the Brazilian city of Manaus confirms part of the world’s largest rainforest is suffering its worst drought, little more than two years after its most significant flooding.