{"id":44,"date":"2022-12-27T14:50:05","date_gmt":"2022-12-27T14:50:05","guid":{"rendered":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/chapter\/differences-in-size-small-and-large-aquifers-aquifer-systems\/"},"modified":"2022-12-29T00:50:01","modified_gmt":"2022-12-29T00:50:01","slug":"differences-in-size-small-and-large-aquifers-aquifer-systems","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/chapter\/differences-in-size-small-and-large-aquifers-aquifer-systems\/","title":{"raw":"1.4 Differences in Size: Small and Large Aquifers\/Aquifer Systems","rendered":"1.4 Differences in Size: Small and Large Aquifers\/Aquifer Systems"},"content":{"raw":"<div class=\"differences-in-size:-small-and-large-aquifers\/aquifer-systems\">\r\n<h1 class=\"sub-sub\">1.4.1 Criteria<\/h1>\r\n<p class=\"import-Normal\">How is the size of an aquifer defined? <span lang=\"en-GB\" xml:lang=\"en-GB\">For those who see an aquifer as a container (the lithological matrix in which drainable groundwater <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">is<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> stored)<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">,<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> it seems logical to define the size of an aquifer theoretically as its volumetric storage capacity, which equals the bulk volume of the aquifer rock times its mean specific yield. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">Specific yield<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> is the fraction of the bulk aquifer volume occupied by water that can be drained by gravity. Estimating aquifer size according to this concept, however, is in practice possible for only very few aquifers in the world. In most cases, the data required for making such estimates with reasonable accuracy are not available<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> because<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> the aquifers are thick or deep, extend over large areas<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">, and\/or have been scarcely or only partially explored<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">. <\/span><\/p>\r\n<p class=\"import-Normal\"><span lang=\"en-GB\" xml:lang=\"en-GB\">If an aquifer is perceived as a container (matrix) plus its content (groundwater), then one may resort to a more feasible, semi<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">-<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">quantitative approach for comparing or classifying <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">the size of <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">aquifers or aquifer systems. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">This approach<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> is based on the following parameters: (<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">i<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">) horizontal area covered by the aquifer or aquifer system (in most cases reasonably known) and (ii) mean cumulative thickness of the hydraulically productive aquifer zones <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">included in the vertical lithological sequence<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span> <span lang=\"en-GB\" xml:lang=\"en-GB\">I<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">n many cases<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">, the size of an aquifer is<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> only a rough <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">estimate<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span><\/p>\r\n<p class=\"import-Normal\">Tentatively, the following aquifer size classification is proposed:<\/p>\r\n\r\n<ul>\r\n \t<li class=\"import-Normal\">very small: less than 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent;<\/li>\r\n \t<li class=\"import-Normal\">small: 100\u2013500 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent;<\/li>\r\n \t<li class=\"import-Normal\">medium: 500\u20135,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 20\u00a0m cumulative thickness of productive aquifer zones;<\/li>\r\n \t<li class=\"import-Normal\">large: 5,000\u201350,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 50\u00a0m cumulative thickness of productive aquifer zones; and,<\/li>\r\n \t<li class=\"import-Normal\">very large: more than 50,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 100\u00a0m cumulative thickness of productive aquifer zones.<\/li>\r\n<\/ul>\r\n<p class=\"import-Normal\">If the thickness criterion is not met, then the aquifer is classified one class lower <a id=\"_Hlk92915035\"><\/a>than the class corresponding to its area.<\/p>\r\n\r\n<h1 class=\"sub-sub\">1.4.2 Small Aquifers<\/h1>\r\n<p class=\"import-Normal\">In principle, there is no lower limit to the size of an aquifer, but very small permeable bodies in the subsurface\u00a0\u2013\u00a0say, 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> or less in lateral extent\u00a0\u2013\u00a0are rarely identified as a separate aquifer (with a given aquifer name). Notable exceptions include a few small aquifers that span international boundaries:<\/p>\r\n\r\n<ul>\r\n \t<li class=\"import-Normal\">the Abbotsford-Sumas Aquifer, sand and gravel of 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent that provides water supply to 10,000 people in the USA and 100,000 in Canada;<\/li>\r\n \t<li class=\"import-Normal\">the Okanagan-Osoyoos Aquifer, multilayer unconsolidated sedimentary aquifer of 25 km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent shared by Canada and the USA;<\/li>\r\n \t<li class=\"import-Normal\">the Grand Forks Aquifer, unconsolidated sediments 34 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in extent shared by Canada and the USA; and,<\/li>\r\n \t<li class=\"import-Normal\">the Genovese Aquifer, Quaternary fluvio-glacial deposits that are 15-40 m thick of approximately 30 km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent, from which 15-17\u00a0mm<sup class=\"import-GWPNormalsuper\">3<\/sup>\/year of groundwater is abstracted and shared by Switzerland and France. It is the first aquifer in the world with a formal international transboundary aquifer management agreement which has been in force since 1978.<\/li>\r\n<\/ul>\r\n<p class=\"import-Normal\">These examples show that even very small aquifers can be important, which is highlighted by such aquifers being included in transboundary aquifer publications and\/or agendas (Puri and Aureli, 2009; IGRAC, 2015). Also, myriad small aquifers \u2013 often unnamed\u00a0\u2013\u00a0that are entirely located within one country (domestic aquifers) are important locally. Because they are numerous, usually shallow, and often closely linked to surface water (alluvial aquifers)\u00a0thus favorably located to sources of recharge,\u00a0small aquifers provide a significant share of the world\u2019s exploited groundwater. The smallest aquifers are predominantly tapped by self-suppliers, usually for domestic and agricultural purposes; many of them are vulnerable to seasonal depletion, especially in arid regions. Water utilities usually locate their wells in aquifers that are at least a few hundred square kilometers in extent and have sufficient capacity to buffer seasonal and interannual variations in recharge.<\/p>\r\n\r\n<h1 class=\"sub-sub\">1.4.3 Large and Very Large Aquifers\/Aquifer Systems<\/h1>\r\n<p class=\"import-Normal\">With increasing horizontal extent and thickness, aquifers tend to become more complex, interbedded with several aquitards, and often hydraulically connected to other aquifers that are usually located above or underneath. In such cases the term \u2018aquifer systems\u2019 is appropriate. Large aquifer systems play an important role in hydrogeology and as a source of water because together they cover a significant part of the continents and contain huge quantities of groundwater.<\/p>\r\n<p class=\"import-Normal\">Figure\u00a08 shows the approximate location of 70 large or very large aquifers\/aquifer systems scattered over the globe. Table\u00a03 lists their names corresponding to the numbers used to identify them in the figure. The selection consists of two distinct sets: a) 37 so-called mega aquifer systems; and, b) 33 other large aquifers or aquifer systems. The mega aquifer systems are considered to be our planet\u2019s largest aquifer systems (these are discussed in <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">Section 2<\/a>). They contain a large share of all fresh groundwater reserves on earth. Part of the groundwater they store may be of considerable age (i.e., the time elapsed since water entered the aquifer system), up to the order of a million years. The selected \u2018other large aquifers\/aquifer systems\u2019, although belonging to the category \u2018large\u2019 or \u2018very large\u2019, do not necessarily represent the next largest aquifer systems. Rather, aquifers have been selected that are large and also rank among the most well-known in their regions, either because of their importance or as an object of investigation. The selection thus is somewhat subjective.<\/p>\r\n<p class=\"import-Normal\"><img class=\"aligncenter\" src=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-content\/uploads\/sites\/30\/2022\/12\/image9.png\" alt=\"Map showing mega and large aquifers\" width=\"1427\" height=\"726\" \/><\/p>\r\n<p class=\"figcaption-text\"><strong>Figure\u00a0<\/strong><strong>8<\/strong><strong>\u00a0<\/strong><strong>-<\/strong><strong>\u00a0<\/strong>Mega aquifer systems and selected other large aquifers\/aquifer systems around the globe (<strong>Table\u00a0<\/strong><strong>3<\/strong> associates names with the numbers) <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-content\/uploads\/sites\/30\/2022\/12\/image9.png\" target=\"_blank\" rel=\"noopener\">View<\/a> a larger version of this figure.<\/p>\r\n<p class=\"tabcaption-text\"><strong>Table\u00a0<\/strong><strong>3<\/strong><strong>\u00a0<\/strong><strong>-<\/strong><strong>\u00a0<\/strong>Mega aquifer systems and selected other large aquifers\/aquifer systems.<\/p>\r\n\r\n<table style=\"width: 100%; border: none; border-collapse: collapse;\">\r\n<tbody>\r\n<tr style=\"background-color: #f2f2f2;\">\r\n<td style=\"vertical-align: top; padding-right: 1em;\"><strong>#<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><strong>Mega aquifer systems<\/strong><\/td>\r\n<td style=\"vertical-align: top; padding-right: 1em;\"><strong>#<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><strong>Other large aquifers\/aquifer systems<\/strong><\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>AFRICA<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>AFRICA<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">1<\/td>\r\n<td style=\"vertical-align: top;\">Nubian Aquifer System (NAS)<\/td>\r\n<td style=\"vertical-align: top;\">38<\/td>\r\n<td style=\"vertical-align: top;\">Djeffara Aquifer System<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">2<\/td>\r\n<td style=\"vertical-align: top;\">North-Western Sahara Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">39<\/td>\r\n<td style=\"vertical-align: top;\">Tindouf Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">3<\/td>\r\n<td style=\"vertical-align: top;\">Murzuk\u2013Djado Basin<\/td>\r\n<td style=\"vertical-align: top;\">40<\/td>\r\n<td style=\"vertical-align: top;\">Gedaref Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">4<\/td>\r\n<td style=\"vertical-align: top;\">Taoudeni-Tanezrouft Basin<\/td>\r\n<td style=\"vertical-align: top;\">41<\/td>\r\n<td style=\"vertical-align: top;\">Vall\u00e9e de la B\u00e9nou\u00e9<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">5<\/td>\r\n<td style=\"vertical-align: top;\">Senegalo-Mauritanian Basin<\/td>\r\n<td style=\"vertical-align: top;\">42<\/td>\r\n<td style=\"vertical-align: top;\">Volta Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">6<\/td>\r\n<td style=\"vertical-align: top;\">Iullemeden\u2013Irhazer Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">43<\/td>\r\n<td style=\"vertical-align: top;\">Aquif\u00e8re c\u00f4tier<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">7<\/td>\r\n<td style=\"vertical-align: top;\">Lake Chad Basin<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">8<\/td>\r\n<td style=\"vertical-align: top;\">Sudd Basin (Umm Ruwaba Aquifer)<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">9<\/td>\r\n<td style=\"vertical-align: top;\">Ogaden-Juba Basin<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">10<\/td>\r\n<td style=\"vertical-align: top;\">Congo Basin<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">11<\/td>\r\n<td style=\"vertical-align: top;\">Cuvelai-Upper Zambezi Basin (Upper Kalahari)<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">12<\/td>\r\n<td style=\"vertical-align: top;\">Stampriet-Kalahari Basin (Lower Kalahari)<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">13<\/td>\r\n<td style=\"vertical-align: top;\">Karoo Basin<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>NORTH AMERICA<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>NORTH AMERICA<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">14<\/td>\r\n<td style=\"vertical-align: top;\">Northern Great Plains Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">44<\/td>\r\n<td style=\"vertical-align: top;\">Columbia Plateau aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">15<\/td>\r\n<td style=\"vertical-align: top;\">Cambrian-Ordovician Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">45<\/td>\r\n<td style=\"vertical-align: top;\">Snake River Plain aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">16<\/td>\r\n<td style=\"vertical-align: top;\">California\u2019s Central Valley Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">46<\/td>\r\n<td style=\"vertical-align: top;\">Basin and Range aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">17<\/td>\r\n<td style=\"vertical-align: top;\">High Plains Aquifer (Ogallala)<\/td>\r\n<td style=\"vertical-align: top;\">47<\/td>\r\n<td style=\"vertical-align: top;\">Rio Grande aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">18<\/td>\r\n<td style=\"vertical-align: top;\">Atlantic and Gulf Coastal Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">48<\/td>\r\n<td style=\"vertical-align: top;\">Edwards-Trinity aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">49<\/td>\r\n<td style=\"vertical-align: top;\">Mexico Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">50<\/td>\r\n<td style=\"vertical-align: top;\">Yucat\u00e1n karst aquifer system<\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>SOUTH AMERICA<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>SOUTH AMERICA<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">19<\/td>\r\n<td style=\"vertical-align: top;\">Amazon Basin<\/td>\r\n<td style=\"vertical-align: top;\">51<\/td>\r\n<td style=\"vertical-align: top;\">Andean Altiplano aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">20<\/td>\r\n<td style=\"vertical-align: top;\">Maranh\u00e3o Basin (Parna\u00edba Basin)<\/td>\r\n<td style=\"vertical-align: top;\">52<\/td>\r\n<td style=\"vertical-align: top;\">Pantanal aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">21<\/td>\r\n<td style=\"vertical-align: top;\">Guarani Basin (Paran\u00e1 Basin)<\/td>\r\n<td style=\"vertical-align: top;\">53<\/td>\r\n<td style=\"vertical-align: top;\">Yrend\u00e1-Toba-Tarije\u00f1o aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">54<\/td>\r\n<td style=\"vertical-align: top;\">Puelche aquifer<\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>ASIA<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>ASIA<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">22<\/td>\r\n<td style=\"vertical-align: top;\">Arabian Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\">55<\/td>\r\n<td style=\"vertical-align: top;\">Tihama aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">23<\/td>\r\n<td style=\"vertical-align: top;\">Indus Basin<\/td>\r\n<td style=\"vertical-align: top;\">56<\/td>\r\n<td style=\"vertical-align: top;\">Pretashkent aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">24<\/td>\r\n<td style=\"vertical-align: top;\">Ganges-Brahmaputra Basin<\/td>\r\n<td style=\"vertical-align: top;\">57<\/td>\r\n<td style=\"vertical-align: top;\">Lower Central Plain aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">25<\/td>\r\n<td style=\"vertical-align: top;\">West Siberian Basin<\/td>\r\n<td style=\"vertical-align: top;\">58<\/td>\r\n<td style=\"vertical-align: top;\">Cambodia-Mekong Delta aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">26<\/td>\r\n<td style=\"vertical-align: top;\">Tunguss Basin<\/td>\r\n<td style=\"vertical-align: top;\">59<\/td>\r\n<td style=\"vertical-align: top;\">Junggur Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">27<\/td>\r\n<td style=\"vertical-align: top;\">Angara-Lena Basin<\/td>\r\n<td style=\"vertical-align: top;\">60<\/td>\r\n<td style=\"vertical-align: top;\">Ordos Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">28<\/td>\r\n<td style=\"vertical-align: top;\">Yakut Basin<\/td>\r\n<td style=\"vertical-align: top;\">61<\/td>\r\n<td style=\"vertical-align: top;\">Jianghan-Dongting Plain aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">29<\/td>\r\n<td style=\"vertical-align: top;\">Greater North China Plain Aquifer System<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">30<\/td>\r\n<td style=\"vertical-align: top;\">Song-Liao Plain (NE China Plain)<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">31<\/td>\r\n<td style=\"vertical-align: top;\">Tarim Basin<\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>EUROPE<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>EUROPE<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">32<\/td>\r\n<td style=\"vertical-align: top;\">Paris Basin<\/td>\r\n<td style=\"vertical-align: top;\">62<\/td>\r\n<td style=\"vertical-align: top;\">London Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">33<\/td>\r\n<td style=\"vertical-align: top;\">Russian Platform Basins<\/td>\r\n<td style=\"vertical-align: top;\">63<\/td>\r\n<td style=\"vertical-align: top;\">Belgian-Dutch-German Lowland aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">34<\/td>\r\n<td style=\"vertical-align: top;\">North Caucasus Basin<\/td>\r\n<td style=\"vertical-align: top;\">64<\/td>\r\n<td style=\"vertical-align: top;\">Upper Rhine Graben aquifer<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">35<\/td>\r\n<td style=\"vertical-align: top;\">Pechora Basin<\/td>\r\n<td style=\"vertical-align: top;\">65<\/td>\r\n<td style=\"vertical-align: top;\">Aquitanian Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">66<\/td>\r\n<td style=\"vertical-align: top;\">Po Valley aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">67<\/td>\r\n<td style=\"vertical-align: top;\">Pannonian aquifer system<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\">68<\/td>\r\n<td style=\"vertical-align: top;\">Dinaric karst aquifer system<\/td>\r\n<\/tr>\r\n<tr style=\"background-color: #d0cece;\">\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>AUSTRALIA<\/strong><\/td>\r\n<td style=\"vertical-align: top;\"><\/td>\r\n<td style=\"vertical-align: top;\"><strong>AUSTRALIA<\/strong><\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">36<\/td>\r\n<td style=\"vertical-align: top;\">Great Artesian Basin<\/td>\r\n<td style=\"vertical-align: top;\">69<\/td>\r\n<td style=\"vertical-align: top;\">Murray Basin<\/td>\r\n<\/tr>\r\n<tr>\r\n<td style=\"vertical-align: top;\">37<\/td>\r\n<td style=\"vertical-align: top;\">Canning Basin<\/td>\r\n<td style=\"vertical-align: top;\">70<\/td>\r\n<td style=\"vertical-align: top;\">Perth Basin<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p class=\"import-Normal\">Some well-known aquifer systems are not shown by name in Table\u00a03, because they are implicitly included as components of the listed and mapped large aquifer systems. Examples include the Dakota Aquifer (partly) and the Canadian Paskapoo aquifer as components of the Northern Great Plains Aquifer System; the Floridan Aquifer System and the Mississippi Embayment Aquifer System as components of the Gulf and Atlantic Coastal Aquifer System; and the Saq-Ram, Wajid and Umm er Radhuma-Dammam Aquifer Systems as components of the Arabian Aquifer System.<\/p>\r\n<p class=\"import-Normal\"><span lang=\"en-GB\" xml:lang=\"en-GB\">In principle, t<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">his book <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">uses<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> the <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">aquifer<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> and aquifer system<\/span> <span lang=\"en-GB\" xml:lang=\"en-GB\">na<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">mes<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> used in the consulted literature, except when <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">that use<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> would lead to confusion<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> or when deemed unsatisfactory for other reasons<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">A few mega aquifer systems have been renamed, as <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">indicated<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> and explained in <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">Section 2<\/a><\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> Sections <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">2<\/a> and <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/hydrological-regime-of-the-mega-aquifer-systems\/\">3<\/a><\/span> focus exclusively on the mega aquifer systems.<\/p>\r\n\r\n<\/div>","rendered":"<div class=\"differences-in-size:-small-and-large-aquifers\/aquifer-systems\">\n<h1 class=\"sub-sub\">1.4.1 Criteria<\/h1>\n<p class=\"import-Normal\">How is the size of an aquifer defined? <span lang=\"en-GB\" xml:lang=\"en-GB\">For those who see an aquifer as a container (the lithological matrix in which drainable groundwater <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">is<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> stored)<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">,<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> it seems logical to define the size of an aquifer theoretically as its volumetric storage capacity, which equals the bulk volume of the aquifer rock times its mean specific yield. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">Specific yield<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> is the fraction of the bulk aquifer volume occupied by water that can be drained by gravity. Estimating aquifer size according to this concept, however, is in practice possible for only very few aquifers in the world. In most cases, the data required for making such estimates with reasonable accuracy are not available<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> because<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> the aquifers are thick or deep, extend over large areas<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">, and\/or have been scarcely or only partially explored<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">. <\/span><\/p>\n<p class=\"import-Normal\"><span lang=\"en-GB\" xml:lang=\"en-GB\">If an aquifer is perceived as a container (matrix) plus its content (groundwater), then one may resort to a more feasible, semi<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">&#8211;<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">quantitative approach for comparing or classifying <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">the size of <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">aquifers or aquifer systems. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">This approach<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> is based on the following parameters: (<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">i<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">) horizontal area covered by the aquifer or aquifer system (in most cases reasonably known) and (ii) mean cumulative thickness of the hydraulically productive aquifer zones <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">included in the vertical lithological sequence<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span> <span lang=\"en-GB\" xml:lang=\"en-GB\">I<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">n many cases<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">, the size of an aquifer is<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> only a rough <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">estimate<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span><\/p>\n<p class=\"import-Normal\">Tentatively, the following aquifer size classification is proposed:<\/p>\n<ul>\n<li class=\"import-Normal\">very small: less than 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent;<\/li>\n<li class=\"import-Normal\">small: 100\u2013500 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent;<\/li>\n<li class=\"import-Normal\">medium: 500\u20135,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 20\u00a0m cumulative thickness of productive aquifer zones;<\/li>\n<li class=\"import-Normal\">large: 5,000\u201350,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 50\u00a0m cumulative thickness of productive aquifer zones; and,<\/li>\n<li class=\"import-Normal\">very large: more than 50,000 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in horizontal extent and with at least 100\u00a0m cumulative thickness of productive aquifer zones.<\/li>\n<\/ul>\n<p class=\"import-Normal\">If the thickness criterion is not met, then the aquifer is classified one class lower <a id=\"_Hlk92915035\"><\/a>than the class corresponding to its area.<\/p>\n<h1 class=\"sub-sub\">1.4.2 Small Aquifers<\/h1>\n<p class=\"import-Normal\">In principle, there is no lower limit to the size of an aquifer, but very small permeable bodies in the subsurface\u00a0\u2013\u00a0say, 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> or less in lateral extent\u00a0\u2013\u00a0are rarely identified as a separate aquifer (with a given aquifer name). Notable exceptions include a few small aquifers that span international boundaries:<\/p>\n<ul>\n<li class=\"import-Normal\">the Abbotsford-Sumas Aquifer, sand and gravel of 100\u00a0km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent that provides water supply to 10,000 people in the USA and 100,000 in Canada;<\/li>\n<li class=\"import-Normal\">the Okanagan-Osoyoos Aquifer, multilayer unconsolidated sedimentary aquifer of 25 km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent shared by Canada and the USA;<\/li>\n<li class=\"import-Normal\">the Grand Forks Aquifer, unconsolidated sediments 34 km<sup class=\"import-GWPNormalsuper\">2<\/sup> in extent shared by Canada and the USA; and,<\/li>\n<li class=\"import-Normal\">the Genovese Aquifer, Quaternary fluvio-glacial deposits that are 15-40 m thick of approximately 30 km<sup class=\"import-GWPNormalsuper\">2<\/sup> extent, from which 15-17\u00a0mm<sup class=\"import-GWPNormalsuper\">3<\/sup>\/year of groundwater is abstracted and shared by Switzerland and France. It is the first aquifer in the world with a formal international transboundary aquifer management agreement which has been in force since 1978.<\/li>\n<\/ul>\n<p class=\"import-Normal\">These examples show that even very small aquifers can be important, which is highlighted by such aquifers being included in transboundary aquifer publications and\/or agendas (Puri and Aureli, 2009; IGRAC, 2015). Also, myriad small aquifers \u2013 often unnamed\u00a0\u2013\u00a0that are entirely located within one country (domestic aquifers) are important locally. Because they are numerous, usually shallow, and often closely linked to surface water (alluvial aquifers)\u00a0thus favorably located to sources of recharge,\u00a0small aquifers provide a significant share of the world\u2019s exploited groundwater. The smallest aquifers are predominantly tapped by self-suppliers, usually for domestic and agricultural purposes; many of them are vulnerable to seasonal depletion, especially in arid regions. Water utilities usually locate their wells in aquifers that are at least a few hundred square kilometers in extent and have sufficient capacity to buffer seasonal and interannual variations in recharge.<\/p>\n<h1 class=\"sub-sub\">1.4.3 Large and Very Large Aquifers\/Aquifer Systems<\/h1>\n<p class=\"import-Normal\">With increasing horizontal extent and thickness, aquifers tend to become more complex, interbedded with several aquitards, and often hydraulically connected to other aquifers that are usually located above or underneath. In such cases the term \u2018aquifer systems\u2019 is appropriate. Large aquifer systems play an important role in hydrogeology and as a source of water because together they cover a significant part of the continents and contain huge quantities of groundwater.<\/p>\n<p class=\"import-Normal\">Figure\u00a08 shows the approximate location of 70 large or very large aquifers\/aquifer systems scattered over the globe. Table\u00a03 lists their names corresponding to the numbers used to identify them in the figure. The selection consists of two distinct sets: a) 37 so-called mega aquifer systems; and, b) 33 other large aquifers or aquifer systems. The mega aquifer systems are considered to be our planet\u2019s largest aquifer systems (these are discussed in <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">Section 2<\/a>). They contain a large share of all fresh groundwater reserves on earth. Part of the groundwater they store may be of considerable age (i.e., the time elapsed since water entered the aquifer system), up to the order of a million years. The selected \u2018other large aquifers\/aquifer systems\u2019, although belonging to the category \u2018large\u2019 or \u2018very large\u2019, do not necessarily represent the next largest aquifer systems. Rather, aquifers have been selected that are large and also rank among the most well-known in their regions, either because of their importance or as an object of investigation. The selection thus is somewhat subjective.<\/p>\n<p class=\"import-Normal\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter\" src=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-content\/uploads\/sites\/30\/2022\/12\/image9.png\" alt=\"Map showing mega and large aquifers\" width=\"1427\" height=\"726\" \/><\/p>\n<p class=\"figcaption-text\"><strong>Figure\u00a0<\/strong><strong>8<\/strong><strong>\u00a0<\/strong><strong>&#8211;<\/strong><strong>\u00a0<\/strong>Mega aquifer systems and selected other large aquifers\/aquifer systems around the globe (<strong>Table\u00a0<\/strong><strong>3<\/strong> associates names with the numbers) <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-content\/uploads\/sites\/30\/2022\/12\/image9.png\" target=\"_blank\" rel=\"noopener\">View<\/a> a larger version of this figure.<\/p>\n<p class=\"tabcaption-text\"><strong>Table\u00a0<\/strong><strong>3<\/strong><strong>\u00a0<\/strong><strong>&#8211;<\/strong><strong>\u00a0<\/strong>Mega aquifer systems and selected other large aquifers\/aquifer systems.<\/p>\n<table style=\"width: 100%; border: none; border-collapse: collapse;\">\n<tbody>\n<tr style=\"background-color: #f2f2f2;\">\n<td style=\"vertical-align: top; padding-right: 1em;\"><strong>#<\/strong><\/td>\n<td style=\"vertical-align: top;\"><strong>Mega aquifer systems<\/strong><\/td>\n<td style=\"vertical-align: top; padding-right: 1em;\"><strong>#<\/strong><\/td>\n<td style=\"vertical-align: top;\"><strong>Other large aquifers\/aquifer systems<\/strong><\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>AFRICA<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>AFRICA<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">1<\/td>\n<td style=\"vertical-align: top;\">Nubian Aquifer System (NAS)<\/td>\n<td style=\"vertical-align: top;\">38<\/td>\n<td style=\"vertical-align: top;\">Djeffara Aquifer System<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">2<\/td>\n<td style=\"vertical-align: top;\">North-Western Sahara Aquifer System<\/td>\n<td style=\"vertical-align: top;\">39<\/td>\n<td style=\"vertical-align: top;\">Tindouf Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">3<\/td>\n<td style=\"vertical-align: top;\">Murzuk\u2013Djado Basin<\/td>\n<td style=\"vertical-align: top;\">40<\/td>\n<td style=\"vertical-align: top;\">Gedaref Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">4<\/td>\n<td style=\"vertical-align: top;\">Taoudeni-Tanezrouft Basin<\/td>\n<td style=\"vertical-align: top;\">41<\/td>\n<td style=\"vertical-align: top;\">Vall\u00e9e de la B\u00e9nou\u00e9<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">5<\/td>\n<td style=\"vertical-align: top;\">Senegalo-Mauritanian Basin<\/td>\n<td style=\"vertical-align: top;\">42<\/td>\n<td style=\"vertical-align: top;\">Volta Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">6<\/td>\n<td style=\"vertical-align: top;\">Iullemeden\u2013Irhazer Aquifer System<\/td>\n<td style=\"vertical-align: top;\">43<\/td>\n<td style=\"vertical-align: top;\">Aquif\u00e8re c\u00f4tier<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">7<\/td>\n<td style=\"vertical-align: top;\">Lake Chad Basin<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">8<\/td>\n<td style=\"vertical-align: top;\">Sudd Basin (Umm Ruwaba Aquifer)<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">9<\/td>\n<td style=\"vertical-align: top;\">Ogaden-Juba Basin<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">10<\/td>\n<td style=\"vertical-align: top;\">Congo Basin<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">11<\/td>\n<td style=\"vertical-align: top;\">Cuvelai-Upper Zambezi Basin (Upper Kalahari)<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">12<\/td>\n<td style=\"vertical-align: top;\">Stampriet-Kalahari Basin (Lower Kalahari)<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">13<\/td>\n<td style=\"vertical-align: top;\">Karoo Basin<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>NORTH AMERICA<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>NORTH AMERICA<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">14<\/td>\n<td style=\"vertical-align: top;\">Northern Great Plains Aquifer System<\/td>\n<td style=\"vertical-align: top;\">44<\/td>\n<td style=\"vertical-align: top;\">Columbia Plateau aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">15<\/td>\n<td style=\"vertical-align: top;\">Cambrian-Ordovician Aquifer System<\/td>\n<td style=\"vertical-align: top;\">45<\/td>\n<td style=\"vertical-align: top;\">Snake River Plain aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">16<\/td>\n<td style=\"vertical-align: top;\">California\u2019s Central Valley Aquifer System<\/td>\n<td style=\"vertical-align: top;\">46<\/td>\n<td style=\"vertical-align: top;\">Basin and Range aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">17<\/td>\n<td style=\"vertical-align: top;\">High Plains Aquifer (Ogallala)<\/td>\n<td style=\"vertical-align: top;\">47<\/td>\n<td style=\"vertical-align: top;\">Rio Grande aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">18<\/td>\n<td style=\"vertical-align: top;\">Atlantic and Gulf Coastal Aquifer System<\/td>\n<td style=\"vertical-align: top;\">48<\/td>\n<td style=\"vertical-align: top;\">Edwards-Trinity aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">49<\/td>\n<td style=\"vertical-align: top;\">Mexico Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">50<\/td>\n<td style=\"vertical-align: top;\">Yucat\u00e1n karst aquifer system<\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>SOUTH AMERICA<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>SOUTH AMERICA<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">19<\/td>\n<td style=\"vertical-align: top;\">Amazon Basin<\/td>\n<td style=\"vertical-align: top;\">51<\/td>\n<td style=\"vertical-align: top;\">Andean Altiplano aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">20<\/td>\n<td style=\"vertical-align: top;\">Maranh\u00e3o Basin (Parna\u00edba Basin)<\/td>\n<td style=\"vertical-align: top;\">52<\/td>\n<td style=\"vertical-align: top;\">Pantanal aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">21<\/td>\n<td style=\"vertical-align: top;\">Guarani Basin (Paran\u00e1 Basin)<\/td>\n<td style=\"vertical-align: top;\">53<\/td>\n<td style=\"vertical-align: top;\">Yrend\u00e1-Toba-Tarije\u00f1o aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">54<\/td>\n<td style=\"vertical-align: top;\">Puelche aquifer<\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>ASIA<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>ASIA<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">22<\/td>\n<td style=\"vertical-align: top;\">Arabian Aquifer System<\/td>\n<td style=\"vertical-align: top;\">55<\/td>\n<td style=\"vertical-align: top;\">Tihama aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">23<\/td>\n<td style=\"vertical-align: top;\">Indus Basin<\/td>\n<td style=\"vertical-align: top;\">56<\/td>\n<td style=\"vertical-align: top;\">Pretashkent aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">24<\/td>\n<td style=\"vertical-align: top;\">Ganges-Brahmaputra Basin<\/td>\n<td style=\"vertical-align: top;\">57<\/td>\n<td style=\"vertical-align: top;\">Lower Central Plain aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">25<\/td>\n<td style=\"vertical-align: top;\">West Siberian Basin<\/td>\n<td style=\"vertical-align: top;\">58<\/td>\n<td style=\"vertical-align: top;\">Cambodia-Mekong Delta aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">26<\/td>\n<td style=\"vertical-align: top;\">Tunguss Basin<\/td>\n<td style=\"vertical-align: top;\">59<\/td>\n<td style=\"vertical-align: top;\">Junggur Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">27<\/td>\n<td style=\"vertical-align: top;\">Angara-Lena Basin<\/td>\n<td style=\"vertical-align: top;\">60<\/td>\n<td style=\"vertical-align: top;\">Ordos Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">28<\/td>\n<td style=\"vertical-align: top;\">Yakut Basin<\/td>\n<td style=\"vertical-align: top;\">61<\/td>\n<td style=\"vertical-align: top;\">Jianghan-Dongting Plain aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">29<\/td>\n<td style=\"vertical-align: top;\">Greater North China Plain Aquifer System<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">30<\/td>\n<td style=\"vertical-align: top;\">Song-Liao Plain (NE China Plain)<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">31<\/td>\n<td style=\"vertical-align: top;\">Tarim Basin<\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>EUROPE<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>EUROPE<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">32<\/td>\n<td style=\"vertical-align: top;\">Paris Basin<\/td>\n<td style=\"vertical-align: top;\">62<\/td>\n<td style=\"vertical-align: top;\">London Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">33<\/td>\n<td style=\"vertical-align: top;\">Russian Platform Basins<\/td>\n<td style=\"vertical-align: top;\">63<\/td>\n<td style=\"vertical-align: top;\">Belgian-Dutch-German Lowland aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">34<\/td>\n<td style=\"vertical-align: top;\">North Caucasus Basin<\/td>\n<td style=\"vertical-align: top;\">64<\/td>\n<td style=\"vertical-align: top;\">Upper Rhine Graben aquifer<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">35<\/td>\n<td style=\"vertical-align: top;\">Pechora Basin<\/td>\n<td style=\"vertical-align: top;\">65<\/td>\n<td style=\"vertical-align: top;\">Aquitanian Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">66<\/td>\n<td style=\"vertical-align: top;\">Po Valley aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">67<\/td>\n<td style=\"vertical-align: top;\">Pannonian aquifer system<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\">68<\/td>\n<td style=\"vertical-align: top;\">Dinaric karst aquifer system<\/td>\n<\/tr>\n<tr style=\"background-color: #d0cece;\">\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>AUSTRALIA<\/strong><\/td>\n<td style=\"vertical-align: top;\"><\/td>\n<td style=\"vertical-align: top;\"><strong>AUSTRALIA<\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">36<\/td>\n<td style=\"vertical-align: top;\">Great Artesian Basin<\/td>\n<td style=\"vertical-align: top;\">69<\/td>\n<td style=\"vertical-align: top;\">Murray Basin<\/td>\n<\/tr>\n<tr>\n<td style=\"vertical-align: top;\">37<\/td>\n<td style=\"vertical-align: top;\">Canning Basin<\/td>\n<td style=\"vertical-align: top;\">70<\/td>\n<td style=\"vertical-align: top;\">Perth Basin<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"import-Normal\">Some well-known aquifer systems are not shown by name in Table\u00a03, because they are implicitly included as components of the listed and mapped large aquifer systems. Examples include the Dakota Aquifer (partly) and the Canadian Paskapoo aquifer as components of the Northern Great Plains Aquifer System; the Floridan Aquifer System and the Mississippi Embayment Aquifer System as components of the Gulf and Atlantic Coastal Aquifer System; and the Saq-Ram, Wajid and Umm er Radhuma-Dammam Aquifer Systems as components of the Arabian Aquifer System.<\/p>\n<p class=\"import-Normal\"><span lang=\"en-GB\" xml:lang=\"en-GB\">In principle, t<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">his book <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">uses<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> the <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">aquifer<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> and aquifer system<\/span> <span lang=\"en-GB\" xml:lang=\"en-GB\">na<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">mes<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> used in the consulted literature, except when <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">that use<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> would lead to confusion<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> or when deemed unsatisfactory for other reasons<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">. <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">A few mega aquifer systems have been renamed, as <\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">indicated<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> and explained in <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">Section 2<\/a><\/span><span lang=\"en-GB\" xml:lang=\"en-GB\">.<\/span><span lang=\"en-GB\" xml:lang=\"en-GB\"> Sections <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/mega-aquifer-systems\/\">2<\/a> and <a href=\"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/part\/hydrological-regime-of-the-mega-aquifer-systems\/\">3<\/a><\/span> focus exclusively on the mega aquifer systems.<\/p>\n<\/div>\n","protected":false},"author":1,"menu_order":4,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-44","chapter","type-chapter","status-publish","hentry"],"part":97,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapters\/44","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":5,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapters\/44\/revisions"}],"predecessor-version":[{"id":285,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapters\/44\/revisions\/285"}],"part":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/parts\/97"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapters\/44\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/wp\/v2\/media?parent=44"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/pressbooks\/v2\/chapter-type?post=44"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/wp\/v2\/contributor?post=44"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/large-aquifer-systems-around-the-world\/wp-json\/wp\/v2\/license?post=44"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}