The Uatumã River (sometimes spelled Uatamã) is a river flowing through the state of Amazonas in Brazil. It is a northern tributary of the Amazon River, and known for its extensive peacock bass population.It is a blackwater river.
The river flows through the Uatuma-Trombetas moist forests ecoregion. 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. The hydroelectric dam generates an average of 112.2 MW of electricity from the river system and floods a total of 2360 km2 of rainforest around the Uatumã river
