The Guaviare is a tributary of the Orinoco in Colombia. It flows together with the upper Orinoco (until here also called Río Parágua), which it clearly surpasses in length (altogether about 1,760 km) and water flow. Thus, the Guaviare is hydrologically the main stream of the Orinoco system. The Guaviare has its source in two other rivers, the Ariari and the Guayabero, which in turn have their own sources in the eastern part of the Andes. At 1,760 km (1,090 mi) long, it is the longest tributary of the Orinoco and is navigable for 630 km (390 mi) of its total length. The Guaviare is considered the border between the Llanos and the Amazon rainforest. Its main tributary is the Inírida River.
