It is a northern tributary of the Amazon River, and known for its extensive peacock bass population.

[3] During the wet season starting in December, water levels can rise some 25 to 40 feet.

Water levels have been strongly affected by the building of the controversial Balbina Dam on the river in the mid to late 1980s to generate electricity.

[4] From the point where the river emerges from the dam it defines the east boundary of the 374,700 hectares (926,000 acres) Caverna do Maroaga Environmental Protection Area, established in 1990.

This article related to a river in the Brazilian state of Amazonas is a stub.