Amazon river dolphin widespread river dolphins. They are present in six countries in South America: Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela, in an area covering about . The boundaries are set by waterfalls, such as the Xingu and Tapajós rivers in Brazil, as well as very shallow water. A series of rapids and waterfalls in the Madeira River have isolated one population, recognized as the subspecies "I. g. boliviensis", in the southern part of the Amazon basin in Bolivia. They are also distributed in the basin of the Orinoco River, except the Caroni River and the upper Caura River in Venezuela. The
Clearwater river (river type) Madeira (notably Guaporé, Ji-Paraná and Aripuanã) and Paraguay (although heavily influenced by its whitewater tributaries). The Tapajós and Xingu alone account for 6% and 5%, respectively, of the water in the Amazon basin. Examples of clearwater rivers originating in the Guiana Shield include the upper Orinoco (above the inflow of the blackwater Atabapo and whitewater Inírida–Guaviare), Ventuari, Nhamundá, Trombetas, Paru, Araguari and Suriname. Outside South America the classification is not commonly used, but rivers with clearwater characteristics are found elsewhere, such as the upper Zambezi River, certain upland streams in major river basins of South and Southeast Asia, and many