The Amazon River accounts for approximately 1/5 of total world's river flow, and it has the largest drainage basin in the world. There is an ongoing dispute regarding its length, and along with the Nile it is one of the contenders for the position as the longest river in the world. Because of its vast dimensions, it is sometimes called The River Sea (o rio-mar in Portuguese), and at no point is it crossed by bridges.
The area covered by the water of the River and its tributaries more than triples over the course of a year. In an average dry season 110,000 square kilometres (42,000 sq mi) of land are water-covered, while in the wet season the flooded area of the Amazon Basin rises to 350,000 square kilometres (135,000 sq mi). At its widest point the Amazon River can be 11 kilometres (7 mi) wide during the dry season, but during the rainy season when the Amazon floods the surrounding plains it can be up to 45 kilometres (28 mi) wide.
The river systems and flood plains in Brazil, Peru, Ecuador, Colombia and Venezuela whose waters drain into the Solimões and its tributaries are called the "Upper Amazon".
The Japurá River or Caquetá River also called the zhepoorä´ in Latin is a river of c.1,750 mi (2,815 km) long (some sources say 2,414 km) rising as the Caquetá River in the Andes in the Southwest of Colombia. It flows southeast into Brazil, where it is called the Japurá. The Japura enters the Amazon River through a network of channels. It is navigable by small boats in Brazil.
The river is home to a wide variety of fish and reptiles, including enormous catfish weighing up to 200 lbs. and measuring up to six feet in length, electric eels, piranhas, turtles, and caimans. It also serves as a principal means of transportation, being plied by tiny dugout canoes, larger ones, motorboats, and riverboats known locally as "lanchas." These lanchas carry a multitude of cargoes, sometimes being chartered, sometimes even being traveling general stores. The presence of guerrillas and soldiers often severely limits river traffic.
West of the Río Negro the Amazon River receives three more imposing streams from the north-west -- the Yapura, the Içá (referred to as the Putumayo before it crosses over into Brazil), and the Napo. The first was formerly known as the Hyapora, but its Brazilian part is now called the Yapura, and its Colombian portion the Caquetá. Barao de Marajo gives it 600 miles of navigable stretches. Jules Crevaux, who descended it, describes it as full of obstacles to navigation, the current very strong and the stream frequently interrupted by rapids and cataracts. It rises in the Colombian Andes, nearly in touch with the sources of the Magdalena River, and augments its volume from many branches as it courses through Colombia. It was long supposed to have eight mouths; but Ribeiro de Sampaio, in his voyage of 1774, determined that there was but one real mouth, and that the supposed others are all furos or canos. In 1864-1868 the Brazilian government made a somewhat careful examination of the Brazilian part of the river, as far up as the rapid of Cupaty. Several very easy and almost complete water-routes exist between the Yapura and Negro across the low, flat intervening country. Barao de Marajo says there are six of them, and one which connects the upper Yapura with the Vaupés branch of the Negro; thus the Indian tribes of the respective valleys have facile contact with each other.