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Groundwater resources that traverse political boundaries are becoming increasingly important sources of freshwater in international and intranational arenas worldwide. This is a direct extension of the growing need for new sources of freshwater, as well as the impact that excessive extraction, pollution, climate change, and other anthropogenic activities have had on surface waters. It is also a function of the growing realization that groundwater respects no political boundaries, and that aquifers traverse jurisdictional lines at all levels of political geography.

Due to this growing awareness, questions pertaining to responsibility and liability are now being raised in relation to the use, management, exploitation, and governance of cross-border aquifers by stakeholders and policymakers who want to maximize their access to subsurface freshwater, as well as minimize their legal vulnerability and exposure. This is occurring both at the international level where two or more sovereign nations, and at the domestic level where two or more subnational political units, overlay a common aquifer.

The law applicable to transboundary groundwater resources at both levels of governance is presently quite primitive and inadequate. Moreover, the relationship of groundwater law to surface water law is often absent from treaties as well as national laws and regulations. While a few promising trends appear to be emerging in the international realm, clear rules and regulations addressing questions of responsibility and liability in relation to the use, management, exploitation, and administration of transboundary groundwater remains elusive at all level of governance.

To provide a foundation for the development of such norms, this paper explores circumstances under which the use, management, exploitation, or administration of a transboundary groundwater body might cause harm to a neighboring political unit—either to their territory, or to important economic, societal, or other interests—and, thereby, result in legal responsibility and/or liability. It assesses cause and effect relationships with reference to conceptual models of transboundary aquifers developed by Eckstein & Eckstein (2005) and Eckstein (2017). Notions of gaining and losing stream relationships, recharging and non-recharging aquifers, groundwater flow direction, the impact of groundwater pumping, anthropogenic contamination, and other concepts are utilized to describe scenarios in which harm could traverse a political boundary. The paper then translates that analysis into notions of responsibility and liability that are common to the legal realm. This research area is novel and has only marginally been addressed in the domestic interstate context of the United States (Hall & Regalia 2016).

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Paris, France


This publication is available in Open Access under the Attribution-ShareAlike 3.0 IGO (CC-BY-SA 3.0 IGO) license ( By using thecontent of this publication, the users accept to be bound by the terms of use of the UNESCO Open Access Repository ( The present license applies exclusively to the text content of the publication. For the use of any material not clearly identified as belonging to UNESCO, prior permission shall be requested from: or UNESCO Publishing, 7, place de Fontenoy, 75352 Paris 07 SP France. The designations employed and the presentation of material throughout this publication do not imply the expression of any opinion whatsoever on the part of UNESCO concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The ideas and opinions expressed in this publication are those of the authors; they are not necessarily those of UNESCO and do not commit the Organization. The boundaries and names shown and the designations used on the maps of this books do not imply official endorsement or acceptance by the United Nations.


Rosario Sánchez

Book Title

Transboundary Aquifers: Challenges and the way forward

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Conference ISARM2021

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