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
East River (South Dakota) East River (South Dakota) The East River portion of South Dakota refers to the section of the state lying east of the Missouri River. Geographical distinctions between the eastern and western sections of the state were reinforced by differing patterns of European-American settlement and Native American resettlement during the 19th and 20th centuries. The eastern half of South Dakota was heavily glaciated and is largely covered by glacial till and loamy soil, which has lent itself to agricultural uses. The Missouri River roughly follows the 100th meridian in the state, and areas to the west of the meridian receive less