The Amazon River, the most voluminous in the world, is still expanding as it captures water from the Orinoco River, which flows through Colombia and Venezuela. Maya Stokes, Samuel Goldberg, and Taylor Perron, from the Massachusetts Institute of Technology (MIT), made the finding after analyzing the size and velocity of the Casiquiare River, which links the Orinoco to the Rio Negro, a major tributary of the Amazon. The Casiquiare River branches off the Orinoco, the fourth largest river in the world, and diverts about a quarter of its waters to the Rio Negro (Geophysical Research Letters, May 25). The study estimates that the flow of the Casiquiare will continue to increase, and in the distant future will divert all water from the upper Orinoco to the Rio Negro. If this occurs, the area drained by the Amazon basin could expand by up to 40,000 square kilometers. There are signs that several tributaries of the west bank of the Amazon were originally captured from the Orinoco basin.
