Graduation date: 2007With 97% of the world’s freshwater resources stored underground, the connection between groundwater resources to the metrics of space, scale and time common to the geographic study of natural resources has not been extensively investigated by geographers. While nearly 240 transboundary aquifers are mapped across the world, a potential “tragedy” is brewing due to the poorly structured institutional capacity built within river basin treaties and agreements and River Basin Organizations to accommodate the management and governance of these transboundary aquifers. Regimes to manage or govern groundwater remain weak. On the basis of a survey of 400 freshwater treaties and agreements completed as part of this study, about 15% include provisions for groundwater. Very few of the treaties and agreements address transboundary aquifers, the coastal aquifer systems which serve as the water supplies to an increasing number of mega cities with populations exceeding 10 million people, the types of aquifers that store groundwater and respond differently to intensive exploitation, or the three dimensional boundaries of the resource or user domains. Recognized as a common pool resource, groundwater resources serve as an example of a “pure” common pool resource. This is because of the difficulty in excluding users and because of the subtractability of the resource as groundwater is pumped or artificially drained from the subsurface. Yet the management and governance of groundwater resources is challenging and increasingly conflictive not only due to its hidden nature, but also because of the difficulty in placing boundaries around the groundwater resources and user domains. These domain boundaries are three dimensional and change with time. Drawing these domain boundaries is supremely political and morph with changing social and cultural values. The present work incorporates an interdisciplinarity and broad systems approach to explore the geography of groundwater to provide context to an inventory of global groundwater resources and user domains. On the basis of surveys of international law and national policies focusing on groundwater, a previously unrecognized typology was derived for the boundaries for groundwater resources and user domains. This work found that (1) traditional approaches to defining groundwater domains focus on predevelopment conditions, referred to herein as a bona-fide “commons” boundary; (2) groundwater development creates human-caused or fiat “hydrocommons” boundary where hydrology and hydraulics are meshed, and (3) the social and cultural values of groundwater users define a fiat “commons heritage” boundary acknowledging that groundwater resources are part of the “common heritage of humankind”. The significance of this typology is that it is difficult to aggregate demographic, social, and economic data within specific boundaries for groundwater resources for detailed geographic analyses, much less develop international regimes, without agreement on the fundamental unit of analysis. Given the complexity of the geologic and political setting of global groundwater resources, a new paradigm of “post-sovereign governance” was examined as part of this study to assess the applicability of global groundwater governance as opposed to international regimes, including the recognition of the geographic overlap between groundwater and ocean resources through an evaluation of the applicability of a law of the sea model for multilateral collaboration regarding groundwater resources through the Law of the Hidden Sea.