The Rio Negro (Portuguese: Rio Negro [ˈʁi.u neɡɾu]; Spanish : Río Negro [ˈri.o ˈneɣɾo] " Black River ") or Guainía as it is known in its upper part, is the largest left tributary of the Amazon River, the largest blackwater river in the world ( accounting for about 14% of the water in the Amazon basin), and one of the world 's ten largest rivers by average discharge.
Geography
Upper course
The source of the Rio Negro lies in Colombia, in the Department of Guainía where the river is known as the Guainía River. The young river generally flows in an east-northeasterly direction through the Puinawai National Reserve, passing several small indigenous settlements on its way, such as Cuarinuma, Brujas, Santa Rosa and Tabaquén. After roughly 400 km the river starts forming the border between Colombia 's Department of Guainía and Venezuela 's Amazonas State. After passing the Colombian community of Tonina and Macanal the river turns Southwest. Maroa is the first Venezuelan town the river passes.
120 km further downstream the river receives the Casiquiare canal from the right - hand, forming a unique link between the Orinoco and the Amazon river basin. Henceforth the river is called Rio Negro.
Middle course
The river now continues in a southeastern direction passing the Venezuelan town of San Carlos de Río Negro, its largest settlement on the river, and Colombia 's San Felipe.
In this stretch the river is constantly fed with tributaries from both sides, and it quickly grows in size creating large river islands, a common feature for all rivers in the Amazon basin.
