Major watersheds (area sq km)

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.  Most watersheds ultimately drain to the some portion of the World Ocean. 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

  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 agriculture

• Zambia

  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)