2 Mega Aquifer Systems
The term ‘mega aquifer systems’ is used here to denote the world’s largest aquifer systems. This section identifies the thirty-seven largest aquifer systems followed by a concise description of some of their main characteristics. These include horizontal extent, thickness, geological characteristics, estimated fresh groundwater reserves and groundwater quality. The compilation is constrained by the scarcity of publicly accessible information on some of the mega aquifer systems, written in a language understood by the author. Exploration and assessment of the mega aquifer systems have advanced to varying degrees, but in all cases, much remains unknown because of the huge size and great depth of these aquifer systems.