Transboundary Offshore Aquifers: A Search for a Governance Regime

The following essay by Renee Martin-Nagle is a summary of her recently published article entitled: Transboundary Offshore Aquifers: A Search for a Governance Regime, which appears in Vol. 1.2, 2016, pp. 1-79, of Brill Research Perspectives in International Water Law. Ms. Martin-Nagle is a PhD Researcher at the University of Strathclyde and a Visiting Scholar at the Environmental Law Institute. She can reached at renee.martinnagle [at]

In December 2013 an article appeared in Nature magazine describing aquifers lying under continental shelves around the world and containing fresh to slightly brackish water.  Entitled ‘Offshore Fresh Groundwater Reserves as a Global Phenomenon’, the article summarized scientific studies since the 1970s and suggested that the volume of water held in these offshore reserves could amount to twice the volume of groundwater withdrawn from aquifers globally since 1900.  Within days, the global press seized on the article and gleefully announced that the global water crisis had been solved.  Intrigued by the possibilities, I determined to understand the scientific support for such claims as well as the potential they held for supplementing existing freshwater supplies.  Moreover, I began to wonder what governance regime might apply in the likely event that one or more of these offshore aquifers straddled an international border  Since the topic of sharing transboundary offshore aquifers has not been addressed previously, there was no template to follow.  However, logic suggested that a governance regime for the these unique aquifers should be influenced by at least three current regimes: legal principles embodied in the UN Convention on the Law of the Sea (‘UNCLOS’), legal principles applicable to transboundary offshore hydrocarbon development, and legal principles that have evolved for transboundary land-based freshwater resources.

Global_Sumarine_Aquifers1My article begins with an explanation of the origins of offshore aquifers.  Not surprisingly, they were formed in the distant past, when meteoric and geological conditions were different than they are today.  During the last glacial maximum between 26,500 and 19,000 years ago, sea levels were much lower than they are today.  At that time the current continental shelves were actually part of the continental coastlines and were, therefore, exposed to rain and other meteoric conditions.  Over thousands of years, freshwater became entrapped between confining layers that were generated by the same natural processes that produced other land-based confined aquifers.  As glaciers melted and sea levels rose, the confining layers protected the now-offshore freshwater aquifers from saltwater intrusion.

With this background, the article proceeds to analyze three legal regimes in search of guidance on how these resources might be governed in transboundary circumstances.  It begins by looking at the UN Convention on the Continental Shelf (the precursor to UNCLOS) and its equidistant method for apportioning shared natural maritime resources among nations with adjacent and opposite coasts.  It then considers the assessment of the International Court of Justice in the North Sea Cases, which rejected the equidistant approach, urged nations to seek equitable solutions based on locally-specific facts and circumstances, and referenced the unity of a deposit. UNCLOS followed the ICJ guidance in advising nations to seek equitable solutions.

Global_Sumarine_Aquifers2Following the North Sea Cases, the oil and gas industry quickly filled the void by developing its own legal mechanism, which is the second regime assessed in my article.  Under that regime, and in harmony with the ICJ’s suggestion to preserve the unity of deposits, the industry utilized a system called unitization where parties sharing a resource appoint a single operator to exploit that reserve, with their respective shares being pre-determined in the applicable agreement.  The concept of unitization later evolved into joint development agreements where nations agreed on an operator for both exploration and exploitation of the resource.

The third regime considered in my study is the body of law that has developed for land-based groundwater resources.  While there are only four ratified treaties and several sets of guidance that address transboundary aquifers, certain concepts for land-based water have evolved to the point of representing accepted principles of customary international law.  Principles such as reasonable and equitable use, no significant harm, cooperation, and sharing of information have been enshrined in treaties for surface water and have also influenced principles for sharing hydrocarbon resources.

After examining these three bodies of law, I propose suggestions for a governance regime for transboundary offshore aquifers that incorporates the best aspects of each of them while still bearing in mind practical aspects of resource development.  Whether this regime will be needed in the near future remains to be seen. Nonetheless, by offering this analysis, I hope to begin the conversation and lay the groundwork for the time when offshore aquifers may be used to support existing freshwater supplies.

The entire article is available here.


One Response to “Transboundary Offshore Aquifers: A Search for a Governance Regime”

  1. David B. Brooks says:

    I do not think this comment affects Dr Martin-Nagle’s discussion about possible governance regimes, but it does expand understanding of the source of off-shore aquifers. They can also occur because of synclinal formations that are permeable but held between non-permeable formations above and below. If the synclines are exposed to the surface offshore, one has offshore aquifers. Such is the case just offshore much of the Lebanese coast, and in some cases the flow is large enough and forceful enough so that one can dip a cup into the “sea” and drink fresh water from 100 m down.

    To the best of my knowledge, only those aquifers that surface with a few metres from the shore have been exploited. And engineering-economic analysis at American University of Beirut has indicated that on shore wells would be the better way exploit the larger offshore ones. Of course, if the aquifer lies athwart an international border, all of the concerns expressed by Dr Martin-Nagle would apply. However, if they are to be tapped from onshore drilling, then unitization would likely be most appropriate.