Continental Runoff and River Discharge

Key Takeaways

• Amazon discharge: 209,000 to 224,000 m³/s (7.4 to 7.9 million ft³/s)
• Water flowing through the Amazon’s mouth each second would fill 88 Olympic pools
• South America: 29% of global runoff, 12% of Earth’s land
• Europe: just two rivers in the world’s top 30 by discharge

Water resources don’t distribute evenly across the planet. South America generates nearly 30% of global runoff while covering just 12% of Earth’s land surface. Europe produces only 6% of the world’s runoff despite its numerous rivers and relatively wet climate. Some regions have far more water than they need. Others don’t have enough.

A cartogram reshapes continents according to their annual runoff volume. South America swells. Europe and Australia shrink.

Runoff by Continent

The world generates 47,884 km³ of runoff per year (11,488 mi³). Distribution across continents:

Continent	Annual Runoff (km³)	Annual Runoff (mi³)	Percentage
South America	13,896	3,333	29%
Asia	13,571	3,255	28%
North America	7,538	1,808	16%
Africa	6,944	1,666	14%
Oceania	3,026	726	6%
Europe	2,909	698	6%

South America and Asia produce similar amounts. But Asia covers more than twice the land and holds 60% of the world’s population. South America? Only 6% of global population on 29% of the water.

Brazil experiences water shortages in its northeast even though the country sits on massive freshwater resources. Northern China imports water despite Asia generating seemingly adequate runoff. The issue isn’t total volume but where water actually flows. The visualization below, created by VisualCapitalist, shows the average discharge of the world’s most powerful rivers, the continents on which they are located, and the countries through which they flow.

Top 30 Rivers

The Amazon discharges 209,000 to 224,000 m³/s depending on season (7.4 to 7.9 million ft³/s). The Ganges-Brahmaputra-Meghna, Congo, Orinoco, Yangtze, Río de la Plata, Mississippi, and Yenisei are the next seven largest rivers. Combined, they nearly match the Amazon by itself. One river moving about 20% of all freshwater into the oceans!

Rank	River System	Region	Discharge (m³/s)	Discharge (ft³/s)
1	Amazon–Ucayali–Apurímac	South America	224,000	7,910,000
2	Ganges-Brahmaputra-Meghna	Asia	42,800	1,511,000
3	Congo	Africa	41,400	1,462,000
4	Orinoco	South America	39,000	1,377,000
5	Yangtze	Asia	31,900	1,126,000
6	Río de la Plata	South America	27,225	961,000
7	Mississippi	North America	21,300	752,000
8	Yenisei	Asia	20,200	713,000
9	Lena	Asia	18,300	646,000
10	St. Lawrence	North America	17,600	621,000
11	Mekong	Asia	15,856	560,000
12	Irrawaddy	Asia	15,112	534,000
13	Ob	Asia	13,100	463,000
14	Amur	Asia	12,360	436,000
15	Tocantins	South America	11,796	416,000
16	Pearl (Xi)	Asia	10,700	378,000
17	Mackenzie	North America	9,800	346,000
18	Volga	Europe	8,380	296,000
19	Magdalena	South America	8,058	285,000
20	Niger	Africa	7,900	279,000
21	Columbia	North America	7,407	262,000
22	Fly	Oceania	7,355	260,000
23	Yukon	North America	6,860	242,000
24	Salween	Asia	6,600	233,000
25	Danube	Europe	6,510	230,000
26	Kapuas	Asia	6,012	212,000
27	Indus	Asia	5,589	197,000
28	Mamberamo	Oceania	5,500	194,000
29	Sepik	Oceania	5,000	177,000
30	Essequibo	South America	4,951	175,000

The Ganges-Brahmaputra-Meghna sits at number two with 42,800 m³/s (1.5 million ft³/s). Still under 20% of the Amazon. Hundreds of millions across India and Bangladesh rely on this system draining the Himalayas.

The Congo ranks third at 41,400 m³/s (1.5 million ft³/s). It crosses the equator twice. Different basin sections hit wet season at different times, keeping flow more consistent year-round than most tropical rivers.

Six South American rivers appear in the top 20. Asia places seven across a continent three times larger. Africa has two. The Volga ranks 18th at 8,380 m³/s (296,000 ft³/s). The Danube sits at 25th with 6,510 m³/s (230,000 ft³/s).

The Nile doesn’t make this list. Africa’s longest river discharges around 3,075 m³/s (109,000 ft³/s). The Sahara evaporates most of its water before the Mediterranean. Length and discharge don’t correlate.

South America controls nearly a third of global runoff using one-eighth of the land. The Amazon in one year moves what most rivers move in a decade.