Iriri River Terra do Meio Ecological Station. The river varies greatly in volume depending on the season, and in the dry season include waterfalls, rocks and rapids. The Iriri River flows through the Tapajós-Xingu moist forests ecoregion. The river is rich in fish, including many species found only here and in the Xingu. Large sections remain unexplored due to its remoteness in a region surrounded by Amazon rainforest, and sections with strong current and cataracts. 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
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,