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
Tapajós-Xingu moist forests the ecoregion blends into the Mato Grosso seasonal forests ecoregion. Elevations range from above sea level along the Amazon to in the south. The ecoregion mostly lies on the undulating terrain of the ancient Brazilian Shield. Soils are often rich in nutrients, but poor soils are found in the higher areas. The main rivers are blackwater, with little or no suspended sediment. The largest is the Iriri, a tributary of the Xingu. Others are the Jamanxim, Curuá, Crepori, Curuá Una, and Jaraucu. The ecoregion is in the neotropic ecozone and the tropical and subtropical moist broadleaf forests biome. The Köppen