The Rio Uatumã is a blackwater river approximately 660 kilometers long, flowing through the state of Amazonas in Brazil before joining the Amazon River as a northern tributary at approximately 2°24′55″S, 57°34′38″W. Its dark, tannin-stained waters are characteristic of Amazonian blackwater systems, and the river passes through the Uatuma-Trombetas moist forests ecoregion, a landscape of dense rainforest with abundant wildlife including monkeys and other fauna typical of the Amazon basin.

Water levels on the Uatumã fluctuate dramatically with the seasons. The wet season begins in December, and during this period water levels can rise between 25 and 40 feet, fundamentally altering the character of the river and the surrounding flooded forest. This extreme seasonal variation is a critical planning consideration for any paddling trip. The Balbina Dam, a hydroelectric facility constructed on the river in the mid-to-late 1980s, has significantly altered the river's hydrology. The dam flooded approximately 2,360 square kilometers of rainforest and created an extensive reservoir system. The average discharge of the river is approximately 2,200 cubic meters per second.

The Balbina reservoir area is a productive fishing destination, particularly for peacock bass, and the broader river system contains numerous small streams and lagoons accessible from the main channel. The town of Uatumã sits along the river and serves as a point of access and resupply. Boat-building workshops are also located along the river in this area.

Kayaking in the backwater areas of the river system is possible, with paddlers reporting calm conditions and wildlife sightings in the flooded forest margins. Given the scale of seasonal flooding and the presence of the Balbina reservoir, paddlers should be prepared for a remote, expedition-style environment with limited infrastructure. The river's remoteness and the size of the flooded reservoir zone mean that self-sufficiency and careful route planning are essential for any paddling venture on this system.