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
Amazon River the northern slope of the valley. The drainage area of the Amazon basin above Óbidos city is about , and, below, only about (around 20%), exclusive of the of the Tocantins basin. The Tocantins River enters the southern portion of the Amazon delta. In the lower reaches of the river, the north bank consists of a series of steep, table-topped hills extending for about from opposite the mouth of the Xingu as far as Monte Alegre. These hills are cut down to a kind of terrace which lies between them and the river. On the south bank, above the Xingu,