A hotly debated subject has emerged under the context of transboundary aquifers (TBA). When planning any type of arrangement to manage an aquifer spanning two or more jurisdictions, MoU, Minutes, legally binding agreements, etc., what should be managed—the aquifer or the groundwater flowing through the aquifer? Is there a trend of misunderstanding between the two terms? In the realm of hydrogeology, there is no dispute on the existence of clarity about the differences between groundwater and aquifers. However, this does not seem to be the case for the law and policy literature, which are strong components of any type of agreement to share a TBA. Most of the concepts relative to aquifers and groundwater are well known in physical and chemical hydrogeology, but when groundwater and/or aquifers traverse two jurisdictions, other factors, not the least the boundaries of aquifers, acquire a more complex meaning. Groundwater sciences need to imbed other interrelated aspects with TBA, such as cooperation, collaboration, social interaction, agreements, prejudices, asymmetries, shared management, and others. A new vocabulary, new concepts, and more accuracy in terminology have emerged over the last 20 years under ISARM (Internationally Shared Aquifer Resources Management). However, there are disagreements because cultural, political, economic, and social factors differ around the world. In addition to its natural boundaries, jurisdictional boundaries need to be added to the TBA. Two examples of contrasting conceptual definitions of aquifers are the Groundwater Bodies in Europe, and the Administrative Aquifers in Mexico. In the former, aquifers are defined by jurisdictional boundaries (sub-units in river basins crossing jurisdictional borders); in the latter, aquifers are defined by administrative boundaries (delimited by basin aquifer boundaries, or state geographical boundaries within the country); in both cases the natural boundaries of aquifers are neglected in the management. Through ISARM we have come to a point where we cannot talk only of aquifers (being transboundary) while ignoring the scales of the dynamics of groundwater either as a flux, or in storage. The issues arrive when we plan and try to implement shared management. In that case, which one should be used? Well, that is not in the menu, that is à la carte; it depends on specific conditions and local circumstances. We cannot manage the same situation in a TBA located in an arid region with fossil groundwater (e.g., Nubian), as compared to one located in a humid region with “modern” recharge (e.g., Guarani). It has become contentious defining the unit of management in the transboundary context. There seems to be a paradigm shift in the way aquifers are perceived and studied when dealing with multiple jurisdictions with transboundary issues; the very nature of the TBA concept is still being debated. Should the complete aquifer be considered? One practice requires parsing out aquifers by dividing them into groundwater flow systems and identifying their relations to each other based on scientific, social, economic and political needs, and issues. Another approach claims that for simpler locally-based groundwater management scenarios, effective TBA areas could be defined by identifying the priority areas of an aquifer using “pumping hot spots.” As this practice is constantly evolving, the concept of groundwater management units under the TBA context will be further defined as new study cases are completed. In large and small TBA, such as the Guarani, and the Genevese, the emphasis is in the shared management of groundwater (the resource), while at the same time recognizing the nature and extent of the aquifers (the container). The Draft Articles on the Law of Transboundary Aquifers (DA) were adopted with UN General Assembly resolution #63 in 2008 (ILC 2008). This non-legally binding resolution recommends shared management of TBAs, without mentioning groundwater (article 14). The DA provided a definition of TBA where: only the saturated zone is considered aquifer, only aquifers with modern recharge, and aquifers including other resources within the aquifer (“utilization of TBA includes extraction of heat, minerals, and storage and disposal of any substance”; art. 2). These would imply that shared management of a TBA would not only be about groundwater. Management of groundwater at the scale closer to the jurisdictional boundaries, should be chosen rather than the full aquifer. Managing shared groundwater, however, requires new elements, e.g., social, economic, and political needs, to complement the knowledge of groundwater dynamics; these new parameters need be incorporated into the groundwater flow systems closer to the jurisdictional boundaries. Ideally, we should privilege shared groundwater management, and at the same time, improve shared governance of the full aquifer to avoid aquifer misuse (overdraft, land subsidence, contamination).
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Aug 29, 2023
Imad Antoine Ibrahim 
Open Access
