GUAPOR RIVER

Portuguese Rio Guapor, Spanish Ro Itnez, river flowing through northeastern Bolivia and west central Brazil. The river rises in the Serra (mountains) dos Parecis in Mato Grosso state, Brazil, and loops southward, westward, and then north-northwestward past Mato Grosso city. After receiving the Rio Verde, it continues northwestward, forming the border between Bolivia and Brazil and emptying into the Mamor River (q.v.) above the town of Guajar-Mirim. The Guapor is the largest affluent of the Mamor and is navigable along its 1,087-mi (1,749-km) course at any season of the year. It flows through a region of tropical rain forest that is almost uninhabited except for occasional settlements of Indians and mestizos along the banks. In contrast with the brown, silt-laden Mamor, the Guapor has unusually clear water. For several miles below their juncture, the identity of the two streams can still be readily perceived. Historically, the region was witness to numerous frontier conflicts between the Spanish and the Portuguese and the struggles of both with hostile Indians. Forte Prncipe da Beira, constructed near the confluence of the Guapor and the Mamor in the late 18th century, is a reminder of this era.