There are three major river systems in South America, and those are the Amazon, Paraná and Orinoco. Together with Madeira and Tocantins they conform the list of the top five longest rivers in South America. We'll attempt to review these and other relevant watercourses by country.
One of the longest two rivers on Earth - the other being the Nile river in Africa - the Amazon drains an area of some 6,915,000 km² (2,722,000 mile²), or about 40 percent of South America. After a course of about 7,200 km (4,800 mi) through the interior of Peru and across Brazil, it enters the Atlantic Ocean, near Belem. Its estuary reaches up to 150 miles wide.
During rainy season, the quantity of fresh water released to the Atlantic Ocean is about 184,000 m³ per second (6.5 million ft³/s), making it responsible for a fifth of the total volume of fresh water entering the oceans worldwide. It has the greatest total flow of any river, estimated to be superior than the Mississippi, Nile, and Yangtze rivers combined.
It originates as a stream from Nevado Mismi in the Peruvian Andes. Flowing into Lake Lauricocha and then the Apurímac river - tributary of the Ucayali - which in turn joins the Marañón to form the actual Amazon.
Second longest in the list of South America rivers comes the Paraná, running through Brazil, Paraguay and Argentina for some 4,880 km (3,030 mi). It merges first with the Paraguay River and then farther downstream with the Uruguay River to form the Río de la Plata and empties into the Atlantic Ocean.
The Paraná river is formed at the confluence of the Paranaiba and Grande rivers in southern Brazil, and the actual name comes from the Tupi-Guarani word "para rehe onáva", meaning "as big as the sea". The Paraná-Paraguay river system provides drinking water, food, energy and transportation to more than 70 million people in the continent.
The drainage basin of the Orinoco covers 880,000 square km (340,000 sq mi), with 76 % of it in Venezuela and the remainder in Colombia. With an extension of 2,140 km (1,330 mi), it originates near the Venezuelan-Brazilian border, precisely Cerro Delgado-Chalbaud, in the Parima range, located in the western part of the Guiana Shield.
It receives several names before discharging into the Gulf of Paría and the Atlantic Ocean: Upper, Middle, Lower and Delta Amacuro, conforming a very large delta that branches off into hundreds of rivers and waterways that flow through 41,000 km2 (16,000 sq mi) of swampy forests of about 370 km (230 mi) at its widest.
Although considered a tributary of the Amazon, it's not quite so, since its waters flow into the Atlantic Ocean alongside those of the Amazon. It runs for about 2,640 km through four Brazilian states, Goiás, Tocantins, Maranhão and Pará. It gives its name to one of Brazil's newest states, created in 1988.
The Tocantins - whose name comes from Tupi-Guarani language meaning "toucan's beak" - originates in the Serra dos Pireneus, Muncipality of Pirenópolis, State of Goiás.
Spanning some 3,250 km (2,020 mi), the Madeira river is the Amazon's largest and most important tributary. It is formed by the junction of the Beni and Mamoré rivers on the Bolivia-Brazil border. At its mouth is Ilha Tupinambarana, located in the State of Amazonas.
Bordered by rivers of the Amazon system - Amazon, Madeira, Sucunduri, and Abacaxis- Ilha Tupinambarana is a former fluvial island that has been split into four completely separate parts by natural channnels, so it's not longer one island, but four.
With a combined area of around 11,850 km², it is the second largest fluvial group of islands in the world after Ilha do Bananal, in southwestern Tocantins, Brazil. Bananal Island is a nature reserve as well as cultural preserve for indigenous people.
Also tributaries of the Amazon river, Rio Negro, Xingu and São Francisco are major watercourses in Brazil. With a length of 2,250 km (1,400 mi), Rio Negro is the largest left tributary of the Amazon and the largest blackwater river in the world. Its actual name - Black river - arises from the fact that it looks black from afar. Near Manaus, at the point of joining the Amazon/ Solimões, it's known as the "Meeting of Waters".
Southeast tributary of the Amazon River, Xingu river flows from central Mato Grosso for 1,979 km (1,230 miles). Some 25,000 indigenous people from several distinct ethnic groups live along its shores. São Francisco is the longest river that runs entirely in Brazilian territory, with a length of 2,830 km (1,758 mi).
Its source is the Canastra mountain range in the State of Minas Gerais and traverses five States before discharging in the Altantic Ocean.
Magdalena river takes its name from the Christianity figure of Mary Magdalene and it's Colombia's most important watercourse. It flows for roughly 1,497 km (930 mi), making it the principal artery of the country and a connection to the Caribbean. Its drainage basin covers a surface of 27.3 million hectares (105,000 sq mi) and it's considered that 86% of the country's gross domestic product is generated there.
Ecuador's two main water systems are the Esmeraldas River (80 km in length) in the North and the Guayas (389 km) in the South. The Guayas is the national river of Ecuador and the most important river in South America that does not flow into the Atlantic Ocean. In the Oriente region, the most important rivers are Pastaza (710 km - 441 mi), Napo (1,130 km - 702 mi), and Putumayo (1,610 km - 1,000 mi).
Ucayali is Peru's longest river with a length of 1,771 km (1,100 mi). Together with Marañón river, they conform the Amazon river. The Marañón River (1,414 km - 879 mi) begins in the Huánuco Region, but its true source lies further up, with the confluence of Lawriqucha and Nupe Rivers.
The list of the top ten rivers in Peru includes as well the Putumayo (it begins in southwestern Colombia), Yavarí (1,184 km - 736 mi), Huallaga (longest river in Peru that doesn’t flow directly into the Amazon), Urubamba (862 km - 536 mi), Mantaro (724 km - 450 mi), Apurímac (690 km - 429 mi), the Napo - that begins in Ecuador - and the mighty Amazon river, its birthplace.
Apart from Paraná - Argentina's longest river - the list of the top five includes Uruguay river (1,838 km - 1,142 mi) that finds it source in the Serra do Mar in Brazil, where the Canoas River and the Pelotas River are joined. Together with the Paraná River, the Uruguay forms the Río de la Plata estuary and is part of the boundaries of Brazil, Argentina and Uruguay,
Rio Negro 550 km (342 mi) originates from the junction of the Limay River and Neuquén River and flows to the Atlantic ocean. Bermejo river (1,060 km - 660 mi) flows from Bolivia to the Paraguay River in Argentina. Pilcomayo - its name comes from the Quechua Pillkumayu meaning "red river" - has a length of 1,100 km (680 mi) long and is the longest western tributary of the Paraguay river.
Colorado river - 1,000 km (620 mi) - is located in the South of the country and marks most of the political boundary between the Argentine provinces of Neuquén and Mendoza, and between Rio Negro and La Pampa.
Although the Futaleufú or "Futa" - 105 km (65 miles) in length - is very well known internationally for withewater rafting and kayaking, it ranks fifth in the list of the top five rivers in Chile. Loa (440 km) is the country's longest river and the main watercourse in the Atacama desert, followed by Bío Bío (380 km), Maipo (250 km) and Cachapoal river (250 km).