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
North Fork American River Big Granite Creek then the North Fork of the American River come in from the right. The canyon shallows as the river turns southwest, carving through the Sierra foothills, then turning abruptly south near Colfax. About downstream, it receives Shirttail Creek from the left then is impounded in Lake Clementine (or North Fork Lake) which is formed by the North Fork Dam, built in 1939 to contain hydraulic mining debris. Below the dam, the river bends south, passing under the Foresthill Bridge, the highest bridge in California, then receives the Middle Fork American River, its largest tributary, from the left.