Negro (South America)

Negro (South America), river in South America. It rises as the Guainía River in south-eastern Colombia, flows east, forming part of the boundary between Colombia and Venezuela, then south into Brazil, and south-east until it empties into the Amazon at Manaus, after a course of about 2,253 km (1,400 mi). Its chief tributaries are the Uaupés and Branco rivers; the Brazo Casiguiare connects the Negro with the Orinoco River. The river is so named because of the large amount of black sediment carried in its waters. The waters of the Negro thus remain distinct from those of the Amazon for many miles after they join.