The Orinoco River is the second longest and third largest river in South America, with a length of about 2,140 km and a discharge of about 37,000 m3/s.
The Paraná River is the second largest and fourth longest river in South America, with a length of about 4,880 km and a discharge of about 18,000 m3/s.
The Rio Negro is the largest tributary of the Amazon River and the largest blackwater river in the world, with a length of about 2,250 km and a discharge of about 28,400 m3/s.
The Madeira River is the largest tributary of the Amazon River by volume and the fifth longest river in South America, with a length of about 3,380 km and a discharge of about 31,200 m3/s.
The Ucayali River is the main headwater of the Amazon River and the sixth longest river in South America, with a length of about 2,760 km and a discharge of about 13,700 m3/s.