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
American River just south of where U.S. Route 50 makes a sharp curve northward to descend into Tahoe Valley. The South Fork has multi-use recreational areas, including the Rubicon Trail for motorized adventuring and whitewater rafting venues. The South Fork also features the historic town of Coloma, where the California Gold Rush began in 1848. Trout fishing and recreational gold panning are popular activities on the South Fork. The Silver Fork American River is a tributary of the South Fork American River, that has its origin at Silver Fork Lake The American River watershed crosses multiple climate zones due to the large