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Major watersheds (area sq km)
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This entry lists the major watersheds or catchment areas of major rivers in a country in terms of their area in sq km. Most of the watersheds listed have an area of at least 500,000 sq km, although some smaller but significant watersheds are also included. The watersheds are listed by the ocean into which they drain. When that drainage occurs other than into the ocean proper, italics are used to identify the constituent part of an ocean (e.g., Black Sea). However, some watersheds, known as endorheic basins, drain internally with no external flow to the ocean. An example of an endorheic basin is the Caspian Sea, the World’s largest lake. Given the size of the largest watersheds, they frequently occur across more than one country.
Afghanistan
Indian Ocean drainage: Indus (1,081,718 sq km)Internal (endorheic basin) drainage: Amu Darya (534,739 sq km); Tarim Basin (1,152,448 sq km)
Albania
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Algeria
Atlantic Ocean drainage: Niger (2,261,741 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
Angola
Atlantic Ocean drainage: Congo (3,730,881 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Internal (endorheic basin) drainage: Okavango Basin (863,866 sq km)
Argentina
Atlantic Ocean drainage: Paraná (2,582,704 sq km)Australia
Indian Ocean drainage: (Great Australian Bight) Murray-Darling (1,050,116 sq km)Internal (endorheic basin) drainage: Lake Eyre (1,212,198 sq km)
Austria
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km), (Black Sea) Danube (795,656 sq km)Bangladesh
Indian Ocean drainage: Brahmaputra (651,335 sq km), Ganges (1,016,124 sq km)Belarus
Atlantic Ocean drainage: (Black Sea) Dnieper (533,966 sq km)Belgium
Atlantic Ocean drainage: Seine (78,919 sq km), Rhine-Maas (198,735 sq km)Benin
Atlantic Ocean drainage: Niger (2,261,741 sq km), Volta (410,991 sq km)Bolivia
Atlantic Ocean drainage: Amazon (6,145,186 sq km), Paraná (2,582,704 sq km)Bosnia and Herzegovina
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Botswana
Atlantic Ocean drainage: Orange (941,351 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Internal (endorheic basin) drainage: Okavango Basin (863,866 sq km)
Brazil
Atlantic Ocean drainage: Amazon (6,145,186 sq km), Orinoco (953,675 sq km), Paraná (2,582,704 sq km), São Francisco (617,814 sq km), Tocantins (764,213 sq km)Bulgaria
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Burkina Faso
Atlantic Ocean drainage: Niger (2,261,741 sq km), Volta (410,991 sq km)Burma
Indian Ocean drainage: Brahmaputra (651,335 sq km), Ganges (1,016,124 sq km), Irrawaddy (413,710 sq km), Salween (271,914 sq km)Pacific Ocean drainage: Mekong (805,604 sq km)
Burundi
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Cambodia
Pacific Ocean drainage: Mekong (805,604 sq km)Cameroon
Atlantic Ocean drainage: Congo (3,730,881 sq km), Niger (2,261,741 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
Canada
Atlantic Ocean drainage: Mississippi* (Gulf of Mexico) (3,202,185 sq km, Canada only 32,000 sq km), Nelson (Hudson Bay) (1,093,141 sq km), Saint Lawrence* (1,049,636 sq km, Canada only 839,200 sq km)Arctic Ocean drainage: Mackenzie (1,706,388 sq km)
Pacific Ocean drainage: Yukon* (847,620 sq km, Canada only 823,800 sq km), Columbia* (657,501 sq km, Canada only 103,000 sq km)
note - watersheds shared with the US shown with *
Central African Republic
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
Chad
Atlantic Ocean drainage: Niger (2,261,741 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
China
Pacific Ocean drainage: Amur (1,929,955 sq km), Huang He (944,970 sq km), Mekong (805,604 sq km), Yangtze (1,722,193 sq km)Indian Ocean drainage: Brahmaputra (651,335 sq km), Ganges (1,016,124 sq km), Indus (1,081,718 sq km), Irrawaddy (413,710 sq km), Salween (271,914 sq km)
Arctic Ocean drainage: Ob (2,972,493 sq km)
Internal (endorheic basin) drainage: Tarim Basin (1,152,448 sq km), Amu Darya (534,739 sq km), Syr Darya (782,617 sq km), Lake Balkash (510,015 sq km)
Colombia
Atlantic Ocean drainage: Amazon (6,145,186 sq km), Orinoco (953,675 sq km)Congo, Democratic Republic of the
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Congo, Republic of the
Atlantic Ocean drainage: Congo (3,730,881 sq km)Cote d'Ivoire
Atlantic Ocean drainage: Niger (2,261,741 sq km), Volta (410,991 sq km)Croatia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Czechia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Ecuador
Atlantic Ocean drainage: Amazon (6,145,186 sq km)Egypt
Atlantic Ocean drainage: (Mediterranean Sea) Nile (3,254,853 sq km)Ethiopia
Atlantic Ocean drainage: (Mediterranean Sea) Nile (3,254,853 sq km)France
Atlantic Ocean drainage: Loire (115,282 sq km), Seine (78,919 sq km), Rhine-Maas (198,735 sq km), (Adriatic Sea) Po (76,997 sq km), (Mediterranean Sea) Rhone (100,543 sq km)Gabon
Atlantic Ocean drainage: Congo (3,730,881 sq km)Germany
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km), (Black Sea) Danube (795,656 sq km)Ghana
Atlantic Ocean drainage: Volta (410,991 sq km)Guinea
Atlantic Ocean drainage: Niger (2,261,741 sq km), Senegal (456,397 sq km)Guyana
Atlantic Ocean drainage: Amazon (6,145,186 sq km), Orinoco (953,675 sq km)Hungary
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)India
Indian Ocean drainage: Brahmaputra (651,335 sq km), Ganges (1,016,124 sq km), Indus (1,081,718 sq km), Irrawaddy (413,710 sq km)Iran
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Iraq
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Italy
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km), (Black Sea) Danube (795,656 sq km), (Adriatic Sea) Po (76,997 sq km), (Mediterranean Sea) Rhone (100,543 sq km)Jordan
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Kazakhstan
Internal (endorheic basin) drainage: Tarim Basin (1,152,448 sq km), Amu Darya (534,739 sq km), Syr Darya (782,617 sq km), Lake Balkash (510,015 sq km)Kenya
Atlantic Ocean drainage: (Mediterranean Sea) Nile (3,254,853 sq km)Kosovo
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Kuwait
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Kyrgyzstan
Internal (endorheic basin) drainage: Tarim Basin (1,152,448 sq km), (Aral Sea basin) Amu Darya (534,739 sq km), Syr Darya (782,617 sq km)Laos
Pacific Ocean drainage: Mekong (805,604 sq km)Lesotho
Atlantic Ocean drainage: Orange (941,351 sq km)Libya
Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)Liechtenstein
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km)Luxembourg
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km)Malawi
Atlantic Ocean drainage: Congo (3,730,881 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Mali
Atlantic Ocean drainage: Niger (2,261,741 sq km), Senegal (456,397 sq km), Volta (410,991 sq km)Mauritania
Atlantic Ocean drainage: Niger (2,261,741 sq km), Senegal (456,397 sq km)Mexico
Atlantic Ocean drainage: (Gulf of Mexico) Rio Grande/Bravo (607,965 sq km)Pacific Ocean drainage: (Gulf of California) Colorado (703,148 sq km)
Moldova
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Montenegro
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Mozambique
Indian Ocean drainage: Zambezi (1,332,412 sq km)Namibia
Atlantic Ocean drainage: Orange (941,351 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Internal (endorheic basin) drainage: Okavango Basin (863,866 sq km)
Nepal
Indian Ocean drainage: Brahmaputra (651,335 sq km), Ganges (1,016,124 sq km), Indus (1,081,718 sq km)Netherlands
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km)Niger
Atlantic Ocean drainage: Niger (2,261,741 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
Nigeria
Atlantic Ocean drainage: Niger (2,261,741 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
North Macedonia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Pakistan
Indian Ocean drainage: Indus (1,081,718 sq km)Internal (endorheic basin) drainage: Tarim Basin (1,152,448 sq km), (Aral Sea basin) Amu Darya (534,739 sq km)
Paraguay
Atlantic Ocean drainage: Paraná (2,582,704 sq km)Peru
Atlantic Ocean drainage: Amazon (6,145,186 sq km)Poland
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Romania
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Russia
Arctic Ocean drainage: Kolyma (679,934 sq km), Lena (2,306,743 sq km), Ob (2,972,493 sq km), Pechora (289,532 sq km), Yenisei (2,554,388 sq km)Atlantic Ocean drainage: (Black Sea) Don (458,694 sq km), Dnieper (533,966 sq km)
Pacific Ocean drainage: Amur (1,929,955 sq km)
Internal (endorheic basin) drainage: (Caspian Sea basin) Volga (1,410,951 sq km)
Rwanda
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Saudi Arabia
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Senegal
Atlantic Ocean drainage: Senegal (456,397 sq km)Serbia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Sierra Leone
Atlantic Ocean drainage: Niger (2,261,741 sq km)Slovakia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)Slovenia
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km)South Africa
Atlantic Ocean drainage: Orange (941,351 sq km)South Sudan
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Sudan
Atlantic Ocean drainage: (Mediterranean Sea) Nile (3,254,853 sq km)Internal (endorheic basin) drainage: Lake Chad (2,497,738 sq km)
Suriname
Atlantic Ocean drainage: Amazon (6,145,186 sq km)Switzerland
Atlantic Ocean drainage: Rhine-Maas (198,735 sq km), (Black Sea) Danube (795,656 sq km), (Adriatic Sea) Po (76,997 sq km), (Mediterranean Sea) Rhone (100,543 sq km)Syria
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Tajikistan
Internal (endorheic basin) drainage: Tarim Basin (1,152,448 sq km), (Aral Sea Basin) Amu Darya (534,739 sq km), Syr Darya (782,617 sq km)Tanzania
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Thailand
Indian Ocean drainage: Salween (271,914 sq km)Pacific Ocean drainage: Mekong (805,604 sq km)
Togo
Atlantic Ocean drainage: Volta (410,991 sq km)Turkey (Turkiye)
Indian Ocean drainage: (Persian Gulf) Tigris and Euphrates (918,044 sq km)Turkmenistan
Internal (endorheic basin) drainage: (Aral Sea basin) Amu Darya (534,739 sq km)Uganda
Atlantic Ocean drainage: Congo (3,730,881 sq km), (Mediterranean Sea) Nile (3,254,853 sq km)Ukraine
Atlantic Ocean drainage: (Black Sea) Danube (795,656 sq km), Don (458,694 sq km), Dnieper (533,966 sq km)United States
Atlantic Ocean drainage: (Gulf of Mexico) Mississippi* (3,202,185 sq km); Rio Grande (607,965 sq km); (Gulf of Saint Lawrence) Saint Lawrence* (1,049,636 sq km total, US only 505,000 sq km)Pacific Ocean drainage: Yukon* (847,620 sq km, US only 23,820 sq km); Colorado (703,148 sq km); Columbia* (657,501 sq km, US only 554,501 sq km)
note - watersheds shared with Canada shown with *
Uzbekistan
Internal (endorheic basin) drainage: (Aral Sea basin) Amu Darya (534,739 sq km), Syr Darya (782,617 sq km)Venezuela
Atlantic Ocean drainage: Amazon (6,145,186 sq km), Orinoco (953,675 sq km)Vietnam
Pacific Ocean drainage: Mekong (805,604 sq km)World
summary statement: a watershed is a drainage basin on an area of land where precipitation collects and drains off into a common outlet, such as into a river, bay, or other body of water; oceans ultimately take in the drainage from 83% of all land area; the remaining 17% of the land drains into internal (endorheic) basins, e.g., the Caspian Sea; The World Factbook lists 51 different watersheds across 102 countries; of these, 18 are in Asia, 9 in Europe, 9 in Africa, 8 in North and Central America, 5 in South America, and 2 in Australia; all watersheds with an area of at least 500,000 sq km have been included along with a number of smaller, regionally significant watersheds; together, these watersheds represent the surface hydrology water flows that are the World's primary sources of fresh water for individual consumption, industry, and agricultureZambia
Atlantic Ocean drainage: Congo (3,730,881 sq km)Indian Ocean drainage: Zambezi (1,332,412 sq km)
Zimbabwe
Indian Ocean drainage: Zambezi (1,332,412 sq km)Internal (endorheic basin) drainage: Okavango Basin (863,866 sq km)