Iriri River Iriri River The Iriri River () is a large tributary of the Xingu River in Brazil, in the state of Pará. It is long making it the 116th longest river in the world (with Krishna River, India) and the 15th longest in the Amazon basin. The headwaters are the traditional home of the Panará people. The river rises in the Nascentes da Serra do Cachimbo Biological Reserve, a strictly protected conservation unit established in 2005 in the Serra do Cachimbo. It is one of the headwaters of the Xingu River. It flows for before joining the Xingu, running through the
Xingu-Tocantins-Araguaia moist forests ecoregion rises into the Carajás Mountains, where it becomes interspersed with areas of seasonal forest and cerrado. Population centers include São Félix do Xingu on the Xingu, Porto de Moz, Oeiras do Pará and Gurupá on the Amazon, and Marabá on the Tocantins. The Marajó várzea at the mouth of the Amazon lies to the north. To the west, on the other side of the Xingu River, is the Tapajós-Xingu moist forests. To the northeast is the Tocantins/Pindare moist forests. To the southeast and south the ecoregion blends into the Mato Grosso seasonal forests ecoregion, and in some places directly