List of drainage basins by area

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This is a list of ocean, mediterranean sea, river, and lake drainage basins larger than 400,000 square kilometers (154,440 square miles), sorted by area. It includes drainage basins which do not flow to the ocean (endorheic basins). It does not include the drainage basins for oceanic seas, as the boundaries of these seas are set by convention and do not necessarily correspond to hydrologically coherent areas.

The oceans drain approximately 83% of the land in the world. The other 17% – an area larger than the basin of the Arctic Ocean – drains to internal endorheic basins.

Note that there are substantial areas of the world that do not "drain" in the commonly understood sense. In arctic deserts much of the snowfall sublimates directly into the air and does not melt into flowing water, while in equatorial deserts precipitation may evaporate before joining any substantial water course. However, these areas can still be included in topographically defined basins if one considers the hypothetical flow of water (or ice), and thus nutrients or pollutants, over the surface of the ground (or ice sheet); this is the approach taken here. For example, the Antarctic ice sheet can be divided into basins [2], and most of Libya is included the Mediterranean Sea basin even though almost no water from the interior actually reaches the sea.

Continent color key
Africa	Asia	Europe	North America	Australia	South America	Antarctica

This list is incomplete; you can help by expanding it.

Basin	Type	Continent	Drains to	Basin Area		Notes
Atlantic Ocean	Ocean	multiple	n/a	69,800,000 km²	26,900,000 mi²	^[1]
Arctic Ocean	Mediterranean Sea	multiple	Atlantic Ocean^[2]	23,100,000 km²	8,900,000 mi²	^[1]
Pacific Ocean	Ocean	multiple	n/a	20,300,000 km²	7,800,000 mi²	^[1]
Indian Ocean	Ocean	multiple	n/a	19,400,000 km²	7,500,000 mi²	^[1]
Southern Ocean	Ocean	Antarctica	n/a	14,000,000 km²	5,400,000 mi²	^[1] ^[3]
Eurafrican Mediterranean Sea	Mediterranean Sea	multiple	Atlantic Ocean^[2]	8,500,000 km²	3,300,000 mi²	^[1]
American Mediterranean Sea	Mediterranean Sea	multiple	Atlantic Ocean^[2]	6,200,000 km²	2,400,000 mi²	^[1]
Amazon River	Primary River	South America	Atlantic Ocean	6,144,727 km²	2,372,492 mi²
Congo River	Primary River	Africa	Atlantic Ocean	3,730,474 km²	1,440,344 mi²
Caspian Sea	Lake	Asia/Europe	n/a (endorheic basin)	3,626,000 km²	1,400,000 mi²
Nile River	Primary River	Africa	Mediterranean Sea	3,254,555 km²	1,256,591 mi²
Mississippi-Missouri River	Primary River	North America	Gulf of Mexico	3,202,230 km²	1 236 388 mi²	^[4]
Ob River	Primary River	Asia	Arctic Ocean	2,972,497 km²	1,147,688 mi²
Paraná River	Primary River	South America	Atlantic Ocean	2,582,672 km²	997,175 mi²
Yenisei River	Primary River	Asia	Arctic Ocean	2,554,482 km²	986,291 mi²
Lake Chad	Lake	Africa	n/a (endorheic basin)	2,497,918 km²	964,452 mi²
Black Sea	Mediterranean Sea	multiple	Mediterranean Sea^[2]	2,400,000 km²	930,000 mi²	^[1]
Lena River	Primary River	Asia	Arctic Ocean	2,306,772 km²	890,650 mi²
Niger River	Primary River	Africa	Atlantic Ocean	2,261,763 km²	873,272 mi²
Amur River	Primary River	Asia	Pacific Ocean	1,929,981 km²	745,170 mi²
Mackenzie River	Primary River	North America	Arctic Ocean	1,743,058 km²	672,998 mi²
Yangtze River (Chang Jiang)	Primary River	Asia	Pacific Ocean	1,722,155 km²	664,927 mi²
Baltic Sea	Mediterranean Sea	Europe	Atlantic Ocean^[2]	1,700,000 km²	660,000 mi²	^[1]
Irtysh River	Tributary River	Asia	Ob River	1,673,470 km²	646,130 mi²
Aral Sea	Lake	Asia	n/a (endorheic basin)	1,618,750 km²	625,000 mi²
Madeira River	Tributary River	South America	Amazon River	1,485,218 km²	573,446 mi²
Volga River	Primary River	Europe	Caspian Sea	1,410,994 km²	544,788 mi²
Persian Gulf	Mediterranean Sea	Asia	Indian Ocean^[2]	1,400,000 km²	540,000 mi²	^[1]
Zambezi River	Primary River	Africa	Indian Ocean	1,332,574 km²	514,510 mi²
Missouri River	Tributary River	North America	Mississippi River	1,331,810 km²	514,215 mi²	^[4]
Paraguay River	Tributary River	South America	Paraná River	1,168,540 km²	451,176 mi²
Lake Eyre Basin	Lake	Australia	n/a (endorheic basin)	1,200,000 km²	460,000 mi²
Tarim River	Primary River	Asia	Lop Nur	1,152,447 km²	444,962 mi²
Australasian Mediterranean Sea	Mediterranean Sea	multiple	Pacfic / Indian Oceans^[2]	1,100,000 km²	420,000 mi²	^[1]
Nelson River	Primary River	North America	Hudson Bay	1,093,442 km²	422,180 mi²
Indus River	Primary River	Asia	Indian Ocean	1,081,733 km²	417,659 mi²
Murray River	Primary River	Australia	Indian Ocean	1,072,000 km²	413,900 mi²
St. Lawrence River	Primary River	North America	Atlantic Ocean	1,049,621 km²	405,261 mi²
Ganges River	Primary River	Asia	Indian Ocean	1,016,104 km²	392,320 mi²
Great Slave Lake	Lake	North America	Mackenzie River	976,200 km²	376,913 mi²
Orinoco River	Primary River	South America	Atlantic Ocean	953,598 km²	368,186 mi²
Huang He	Primary River	Asia	Pacific Ocean	945,065 km²	364,892 mi²
Orange River	Primary River	Africa	Atlantic Ocean	941,421 km²	363,485 mi²
Kasai River	Tributary River	Africa	Congo River	925,172 km²	357,211 mi²
Yukon River	Primary River	North America	Bering Sea	847,642 km²	327,276 mi²
Mekong River	Primary River	Asia	Pacific Ocean	805,627 km²	311,054 mi²
Great Lakes	Lake	North America	St. Lawrence River	800,114 km²	308,926 mi²
Danube River	Primary River	Europe	Black Sea	795,686 km²	307,216 mi²
Syr Darya	Primary River	Asia	Aral Sea	782,669 km²	302,190 mi²
Tigris-Euphrates Rivers	Primary River	Asia	Persian Gulf	765,831 km²	295,689 mi²
Tocantins River	Primary River	South America	Atlantic Ocean	764,183 km²	295,053 mi²
Okavango River	Primary River	Africa	Okavango Delta	721,277 km²	278,487 mi²
Negro River	Tributary River	South America	Amazon River	720,114 km²	278,038 mi²
Colorado River (U.S.)	Primary River	North America	Gulf of California	703,132 km²	271,481 mi²
Kolyma River	Primary River	Asia	Arctic Ocean	679,908 km²	262,514 mi²
Columbia River	Primary River	North America	Pacific Ocean	657,490 km²	253,858 mi²
Brahmaputra River	Primary River	Asia	Indian Ocean	651,334 km²	251,481 mi²
Red Sea	Mediterranean Sea	multiple	Indian Ocean^[2]	620,000 km²	230,000 mi²	^[1]
São Francisco River	Primary River	South America	Atlantic Ocean	617,812 km²	238,539 mi²
Ubangi River	Tributary River	Africa	Congo River	613,202 km²	236,759 mi²
Rio Grande	Primary River	North America	Gulf of Mexico	608,023 km²	234,759 mi²
Lake Baikal	Lake	Asia	Angara River	571,000 km²	220,000 mi²
Chari River	Primary River	Africa	Lake Chad	548,747 km²	211,872 mi²
Amu Darya	Primary River	Asia	Aral Sea	534,764 km²	206,474 mi²
Dnieper River	Primary River	Europe	Black Sea	531,817 km²	205,336 mi²
Xingu River	Tributary River	South America	Amazon River	520,292 km²	200,886 mi²
Lake Balkhash	Lake	Asia	n/a (endorheic basin)	512,010 km²	197,688 mi²
Viljuj River	Tributary River	Asia	Lena River	507,874 km²	196,091 mi²
Kama River	Tributary River	Europe	Volga River	507,000 km²	195,754 mi²
Jubba River	Primary River	Africa	Indian Ocean	497,655 km²	192,146 mi²
Great Basin		North America	n/a (endorheic basin)	492,000 km²	190,000 mi²	^[5]
Ohio River	Tributary River	North America	Mississippi River	490,603 km²	189,423 mi²
Tapajos River	Tributary River	South America	Amazon River	486,792 km²	187,951 mi²
Songhua River	Tributary River	Asia	Amur River	459,745 km²	177,509 mi²
Don River	Primary River	Europe	Black Sea	458,703 km²	177,106 mi²
Arkansas River	Tributary River	North America	Mississippi River	435,122 km²	168,002 mi²
Saskatchewan River	Tributary River	North America	Lake Winnipeg	435,000 km²	168,000 mi²
Tobol River	Tributary River	Asia	Irtysh River	426,000 km²	164,480 mi²
Limpopo River	Primary River	Africa	Indian Ocean	421,168 km²	162,614 mi²
Senegal River	Primary River	Africa	Atlantic Ocean	419,659 km²	162,031 mi²
Ayeyarwady River	Primary River	Asia	Indian Ocean	413,674 km²	159,720 mi²
Pearl River	Primary River	Asia	Pacific Ocean	409,458 km²	158,093 mi²
Volta River	Primary River	Africa	Indian Ocean	407,093 km²	157,179 mi²
Colorado River (Argentina)	Primary River	South America	Atlantic Ocean	402,956 km²	155,582 mi²

[edit] Notes

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l This is an approximate value based on geospatial data from the USGS.[1] Approximate values for the area of Greenland and Antarctica were added to this data.
^ ^a ^b ^c ^d ^e ^f ^g ^h Note that the connection between a mediterranean sea (or a large estuary) and its parent ocean usually involves simultaneous inflow and outflow in the lower and upper water layers of the connecting channel. Depending on the salinity of the sea, the upper layer may either flow into or out from the ocean; the bottom layer will flow the opposite direction.
^ The value listed here assumes that the entire continent drains to the ocean, such as through the many ice streams, outlet glaciers, and seasonal glacial streams along the coast. However, there are many small endorheic lakes, for example in the McMurdo Dry Valleys.
^ ^a ^b The Mississippi is not the longest watercourse in the Mississippi-Missouri watershed; the combination of the Lower Mississippi and the Missouri is longer. The Upper Mississippi River could thus be seen as a tributary of that river. See list of rivers by length for more details.
^ The Great Basin is not one unified drainage basin. The largest basin within it drains to the Great Salt Lake; this basin has an area of 54,390 km² (21,000 mi²).