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.
Lullemeden-Irhazer Aquifer System, Murzuk-Djado Basin, North Western Sahara Aquifer, Taoudeni-Tanezrouft Basin
Congo Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Great Artesian Basin, Canning Basin
Indus-Ganges-Brahmaputra Basin
Lower Kalahari-Stampriet Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Amazon Basin, Guarani Aquifer System, Maranhao Basin
Northern Great Plains Aquifer
Congo Basin, Lake Chad Basin
Lake Chad Basin, Nubian Aquifer System
North China Aquifer System (Huang Huai Hai Plain), Song-Liao Plain, Tarim Basin
Ogaden-Juba Basin, Sudd Basin (Umm Ruwaba Aquifer)
Senegalo-Mauritanian Basin
Senegalo-Mauritanian Basin
Indus-Ganges-Brahmaputra Basin
Nubian Aquifer System, North Western Sahara Aquifer System, Murzuk-Djado Basin
Lullemeden-Irhazer Basin, Taodeni-Tanezrouft Basin
Senegalo-Mauritanian Basin, Taodeni-Tanzerouft Basin
Atlantic and Gulf Coastal Plains Aquifer
Lower Kalahari-Stampriet Basin, Upper Kalahari-Cuvelai-Upper Zambezi Basin
Indus-Ganges-Brahmaputra Basin
Lake Chad Basin, Lullemeden-Irhazer Basin, Murzuk-Djado Basin
Lake Chad Basin, Lullemeden-Irhazer Aquifer System
Angara-Lena Basin, Pechora Basin, North Caucasus Basin, East European Aquifer System, West Siberian Basin, Tunguss Basin, Yakut Basin
Senegalo-Mauritanian Basin
Karoo Basin, Lower Kalahari-Stampriet Basin
Nubian Aquifer System, Sudd Basin (Umm Ruwaba Aquifer)
North Western Sahara Aquifer System
Northern Great Plains Aquifer, Cambrian-Ordovician Aquifer System, Californian Central Valley Aquifer System, Ogallala Aquifer (High Plains), Atlantic and Gulf Coastal Plains Aquifer
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
Upper Kalahari-Cuvelai-Upper Zambezi Basin
Upper Kalahari-Cuvelai-Upper Zambezi Basin