The Beni River flows north through Bolivia after rising in the Andean slopes of the Cordillera Real. The Mamoré River is formed by numerous headwaters that drain the Llanos de Moxos. The two rivers form the Madeira River on the border with Brazil.
The Beni River flows north/northeast through Bolivia after rising in the Andean slopes of the Cordillera Real. Fed by various confluents, it flows through plains and the densely forested Yungas north of La Paz. The middle path of the river runs through dense rainforests, joined by the Madidi and Tuichi rivers, which flow through Madidi National Park.
The Tuichi River joins the Beni River upstream from the town of Rurrenabaque. North of Rurrenabaque, the Beni River runs through the Llanos de Moxos or Beni Savanna. The Madre de Dios River joins the Beni River at Riberalta. Then, it flows to its junction with the Mamoré River at Villa Bella, on the Brazilian border.
After approximately 1,600 km (1,000 mi), the Beni and the Mamoré form the Madeira River at Riberalta, constituting Bolivia's extreme northeastern border. Steam navigation is possible at specific points along the Beni during high water (December to May).
Map depicting the Amazon River drainage basin with the Beni River highlighted
The Mamoré River in north-central Bolivia is formed by numerous headwaters that arise on the northern slopes of the Cordillera Real and drain the Llanos de Moxos, or Moxos plain, an ancient lake bed. The Grande River is its main tributary.
The Mamoré generally meanders northward to the Brazilian border, at which point the Guaporé joins it. It constitutes the Bolivia-Brazil border that runs north to Villa Bella. Here, it merges with the Beni River to form the Madeira River.
Due to rapids that occur a few miles above its junction with the Beni, the river's importance as a transport route is limited. However, navigation is possible through the Moxos plain and tropical rainforests to the border towns of Guajará-Mirim, Brazil, and Guayaramerín, Bolivia. Numerous indigenous communities inhabit the banks of the river.
Map depicting the Amazon River drainage basin with the Mamoré River highlighted