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
Terra do Meio Ecological Station. The river varies greatly in volume depending on the season, and in the dry season includes 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 there 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. ==References==