Major aquifers
This entry lists the major (mega) aquifer system(s) that underlie a country, keeping in mind that many of these mega aquifers are so large that they extend under multiple countries. More than 30% of freshwater is held in underground aquifers. There is great variation in the size of such aquifers, but a limited number of very large aquifer systems contain a majority of the World’s groundwater volume in storage.
Algeria
Lullemeden-Irhazer Aquifer System, Murzuk-Djado Basin, North Western Sahara Aquifer, Taoudeni-Tanezrouft Basin
Angola
Congo Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Argentina
Guarani Aquifer System
Australia
Great Artesian Basin, Canning Basin
Bahrain
Arabian Aquifer System
Bangladesh
Indus-Ganges-Brahmaputra Basin
Bolivia
Amazon Basin
Botswana
Lower Kalahari-Stampriet Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Brazil
Amazon Basin, Guarani Aquifer System, Maranhao Basin
Cameroon
Lake Chad Basin
Canada
Northern Great Plains Aquifer
Central African Republic
Congo Basin, Lake Chad Basin
Chad
Lake Chad Basin, Nubian Aquifer System
China
North China Aquifer System (Huang Huai Hai Plain), Song-Liao Plain, Tarim Basin
Colombia
Amazon Basin
Congo, Democratic Republic of the
Congo Basin
Congo, Republic of the
Congo Basin
Egypt
Nubian Aquifer System
Ethiopia
Ogaden-Juba Basin, Sudd Basin (Umm Ruwaba Aquifer)
France
Paris Basin
Gabon
Congo Basin
Gambia, The
Senegalo-Mauritanian Basin
Guinea-Bissau
Senegalo-Mauritanian Basin
India
Indus-Ganges-Brahmaputra Basin
Iraq
Arabian Aquifer System
Jordan
Arabian Aquifer System
Kenya
Ogaden-Juba Basin
Kuwait
Arabian Aquifer System
Libya
Nubian Aquifer System, North Western Sahara Aquifer System, Murzuk-Djado Basin
Mali
Lullemeden-Irhazer Basin, Taodeni-Tanezrouft Basin
Mauritania
Senegalo-Mauritanian Basin, Taodeni-Tanzerouft Basin
Mexico
Atlantic and Gulf Coastal Plains Aquifer
Namibia
Lower Kalahari-Stampriet Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Nepal
Indus-Ganges-Brahmaputra Basin
Niger
Lake Chad Basin, Lullemeden-Irhazer Basin, Murzuk-Djado Basin
Nigeria
Lake Chad Basin, Lullemeden-Irhazer Aquifer System
Oman
Arabian Aquifer System
Pakistan
Indus Basin
Paraguay
Guarani Aquifer System
Peru
Amazon Basin
Qatar
Arabian Aquifer System
Russia
Angara-Lena Basin, Pechora Basin, North Caucasus Basin, East European Aquifer System, West Siberian Basin, Tunguss Basin, Yakut Basin
Saudi Arabia
Arabian Aquifer System
Senegal
Senegalo-Mauritanian Basin
Somalia
Ogaden-Juba Basin
South Africa
Karoo Basin, Lower Kalahari-Stampriet Basin
Sudan
Nubian Aquifer System, Sudd Basin (Umm Ruwaba Aquifer)
Tunisia
North Western Sahara Aquifer System
United States
Northern Great Plains Aquifer, Cambrian-Ordovician Aquifer System, Californian Central Valley Aquifer System, Ogallala Aquifer (High Plains), Atlantic and Gulf Coastal Plains Aquifer
Uruguay
Guarani Aquifer System
World
summary statement: aquifers are underground layers of water-bearing permeable rock formations; they include alluvial formations such as unconsolidated sand and gravel aquifers, sedimentary rock formations of sandstone and karst (carbonate rocks such as limestone) aquifers, as well as volcanic aquifers, and basement aquifers (igneous and metamorphic rocks that underlie sedimentary and volcanic rock sequences); groundwater from aquifers can be extracted using a water well; The World Factbook lists 37 major aquifers across 52 countries; of these, 13 are in Africa, 10 in Asia, 5 in North America, 3 in South America, 4 in Europe, and 2 in Australia; although aquifers can vary in size, the major aquifers listed in The Factbook contain the bulk of the stored volume of groundwater; the fresh water held in these aquifers represents more than 30% of the World's fresh water; in the US, groundwater is primarily used for irrigation and globally, 70% of groundwater withdrawn is used for agriculture; groundwater also supplies almost half of all drinking water worldwide
Zambia
Upper Kalahari-Cuvelai-Upper Zambezi Basin
Zimbabwe
Upper Kalahari-Cuvelai-Upper Zambezi Basin