section_path: Basin and course
section_name: Basin and course
paragraph_text: Basin and course
  
  The Congo's drainage basin covers 4,014,500 km 2 (1,550,000 sq mi), an area nearly equal to that of the European Union. The Congo's discharge at its mouth ranges from 23,000 to 75,000 m 3 /s (810,000 to 2,650,000 cu ft/s), with an average of 41,000 m 3 /s (1,400,000 cu ft/s). The river transports annually 86 million tonnes of suspended sediment to the Atlantic Ocean and an additional 6% of bedload.
  
  The river and its tributaries flow through the Congo rainforest, the second largest rainforest area in the world, after the Amazon rainforest in South America. The third-largest river in the world by discharge volume (at mouth 41,860 m 3 /s), following the Amazon (219,530 m 3 /s) and Ganges – Brahmaputra – Meghna (total discharge at delta 43,950 m 3 /s) rivers; the second-largest drainage basin of any river, behind the Amazon; and is one of the deepest rivers in the world, at depths greater than 220 m (720 ft). Because its drainage basin includes areas both north and south of the Equator, its flow is stable, as there is always at least one part of the river experiencing a rainy season.
  
  The sources of the Congo are in the highlands and mountains of the East African Rift, as well as Lake Tanganyika and Lake Mweru, which feed the Lualaba River, which then becomes the Congo below Boyoma Falls. The Chambeshi River in Zambia is generally taken as the source of the Congo in line with the accepted practice worldwide of using the longest tributary, as with the Nile River.
  
  The Congo flows generally toward the northwest from Kisangani just below the Boyoma Falls, then gradually bends southwestward, passing by Mbandaka, joining with the Ubangi River and running into the Pool Malebo (Stanley Pool). Kinshasa (formerly Léopoldville) and Brazzaville are on opposite sides of the river at the Pool, where the river narrows and falls through a number of cataracts in deep canyons (collectively known as the Livingstone Falls), running by Matadi and Boma, and into the sea at Muanda.
  
  Lower Congo constitutes the "lower" parts of the great river; that is the section of the river from the river mouth at the Atlantic coast to the twin capitals of Brazzaville and Kinshasa. In this section of the river, there are two significant tributaries, both on the left or south side. The Kwilu River originates in the hills near the Angolan border and enters the Congo some 100 km upstream from Matadi. The other is the Inkisi River, that flows in a northerly direction from the Uíge Province in Angola to the confluence with the Congo at Zongo some 80 km (50 mi) downstream from the twin capitals. Because of the vast number of rapids, in particular the Livingstone Falls, this section of the river is not operated continuously by riverboats.