In geography, a confluence is the meeting of two or more bodies of water. Also known as a conflux, it refers either to the point where a tributary joins a larger river, called the main stem, or where two streams meet to become the source of a river of a new name, such as the confluence of the Monongahela and Allegheny rivers in Pittsburgh, Pennsylvania creating the Ohio River.
The term is also used to describe the meeting of tidal or other non-riverine bodies of water, such as two canals or a canal and a lake. A one-mile (1.6 km) portion of the Industrial Canal in New Orleans accommodates the Gulf Intracoastal Waterway and the Mississippi River-Gulf Outlet Canal; therefore those three waterways are confluent there.
The Meeting of Waters (Portuguese: Encontro das Águas) is the confluence between the Rio Negro, a river with dark (almost black coloured) water, and the sandy-coloured Amazon River or Rio Solimões, as it is known the upper section of the Amazon in Brazil. For 6 km (3.7 mi) the river's waters run side by side without mixing. It is one of the main tourist attractions of Manaus, Brazil. The same also happens near Santarém, Pará with the Amazon and Tapajós rivers.
This phenomenon is due to the differences in temperature, speed and water density of the two rivers. The Rio Negro flows at near 2 km per hour at a temperature of 28°C, while the Rio Solimões flows between 4 to 6 km per hour a temperature of 22°C.