Its Brazilian tributaries are comparatively unimportant, but from Bolivia it receives the Baures and the San Miguel, both rising in the Sierras de Chiquitos and flowing north-west across the llanos to the Guapore.
The Baures has one large tributary, the Blanco, and the Itonama (San Miguel) has its origin in Lake Concepcion, lying among the west ranges of the Chiquitos mountains 952 ft.
The first includes the Guapay or Rio Grande, Piray or Sara, Yapacani and Marac6, upper tributaries of the Mamore, and the San Miguel, Blanco, Baures and Paragua, tributaries of the Guapore - both draining the western and northern parts of the department.
The waters find their way to the falls of the Madeira by many great rivers, the principal of which, if we enumerate them from east to west, are the Guapore or Itenez, the Baures and Blanco, the Itonama or San Miguel, the Mamore, Beni, and Mayutata or Madre de Dios, all of which are reinforced by numerous secondary but powerful affluents.
The Guapore presents many difficulties to continuous navigation; the Baures and Itonama offer hundreds of miles of navigable waters through beautiful plains; the Mamore has been sounded by the writer in the driest month of the year for a distance of 500 m.