The following post by Professor Gabriel Eckstein is the seventh in the series of essays related to the entering into force of the 1997 UN Watercourses Convention (see links to all of the essays here). Professor Eckstein is a member of the law faculty at Texas A&M University, directs the International Water Law Project, and edits the International Water Law Project Blog. He can be reached at gabriel [at] internationalwaterlaw.org or gabrieleckstein [at] law.tamu.edu.
With Vietnam’s accession to the 1997 UN Watercourses Convention (UNWC), the global community has taken an important step toward cooperative riparian management of transboundary waters. Although most scholars and UNWC parties have focused on the surface water implications of the Convention, there is another critical component of the instrument that should not be neglected. The UWNC applies to many aquifers worldwide. The purpose of this essay is to consider the scope of the Convention in relation to groundwater resources and place it in the context of emerging international law for transboundary aquifers.
Groundwater: a hidden treasure
Groundwater is the world’s most extracted natural resource. It provides approximately 45% of humanity’s freshwater needs for everyday uses, such as drinking, cooking, and hygiene, and 24% of water used in irrigated agriculture (see here).
Not surprising, groundwater is highly transboundary. While 276 international watercourses traverse the world’s land areas, an ongoing study identified 448 aquifers and aquifer bodies traversing international political boundaries. In places like the Middle East, North Africa, and the Mexico-United States border, transboundary aquifers serve as the primary or sole source of available freshwater for human and environmental sustenance.
Despite their importance, transboundary aquifers have been comparatively ignored in cross-border water management and treaty development. While thousands of agreements have been forged for transboundary rivers and lakes, only a handful directly apply to aquifers that traverse international frontiers. As one of the few international instruments to address this topic, the UNWC provides critical recognition of the important role groundwater resources play in human progress and development, as well as the need to establish principles of law governing this “hidden” but valuable natural resource.
Applicability of the UNWC to groundwater resources
Although the UNWC clearly applies to many of the world’s groundwater resources, it is important to delineate precisely which aquifers are included and excluded from the rubric of the Convention. The UNWC defines “watercourse” to mean “a system of surface waters and groundwaters constituting by virtue of their physical relationship a unitary whole and normally flowing into a common terminus,” and an “international watercourse” as “a watercourse, parts of which are situated in different States.” Parsing out this phraseology reveals a number of important qualifications.
For an aquifer to fall within the scope of the UNWC, it must be a part of a “system of surface waters and groundwaters.” Use of the “system” criterion in the definition implies an interrelationship between multiple and interlinked water bodies. This assessment is supported and complemented by the subsequent definitional language that emphasizes the “physical relationship” and “unitary whole” of the system, and the “common” characterization of a terminus. Hence, solitary transboundary aquifers – such as independent fossil aquifers and rain-fed aquifers – are presumptively excluded from the scope of the UNWC.
It is noteworthy that subsequent to drafting the principles for the UNWC, the UN International Law Commission (ILC) submitted a Resolution on Confined Transboundary Groundwater in which it commended states to be guided by the principles of its work product in regulating independent and hydraulically unrelated transboundary groundwater resources. This progressive recommendation was not incorporated into the UNGA’s final version of the UNWC.
In addition, a textual reading of the two definitions suggests that the Convention applies where the transboundary character exists in any part of the system. Hence, a domestic aquifer is subject to the UNWC if it is hydraulically connected to a transboundary river. Similarly, an internal river would be bound by the terms of the Convention if it is linked to a transboundary aquifer. This latter scenario, however, may be subject to debate. In its Thirty-Second Session Report during its preparatory work to the UNWC, the ILC asserted that “the main stem of a river traversing or forming an international boundary” is the “core” of a watercourse. Additionally, Ambassador Chusei Yamada, who served on the ILC during the drafting of the UNWC and later as Special Rapporteur for the ILC’s Draft Articles on the Law of Transboundary Aquifers (Draft Articles), explained to this author in a private conversation that in its deliberations the ILC, and later the UNGA, never contemplated applying the Convention where the transboundary character of the system could not be found in a surface water body. Given that the qualification has yet to be considered in state practice, it remains unclear how broadly it may be interpreted.
Another criterion affecting the UNWC’s applicability to certain groundwater resources is the phrase “flowing into a common terminus.” The criterion intimates that the interlinked water resources must flow toward the same end point to be subject to the Convention’s regime. The directional flow of rivers and lakes, however, is generally described in two dimensions (from point X to point Y). In contrast, groundwater flow is defined in three dimensions because its movement is dependent on local geological conditions, which can vary throughout the aquifer. As a result, groundwater can flow toward a disparate terminal point from that of a related surface water body. Moreover, while aquifers do sometimes terminate at a single point, such as at a spring, it is more common for aquifers to discharge over an extended geographical area along the entire edge of the aquifer. Accordingly, the Convention does not apply to aquifers that do not share a common terminus with hydraulically connected rivers and lakes.
In summary, the UNWC does apply to groundwater resources. However, the Convention’s definitions narrow its relevance to domestic and transboundary aquifers that are hydraulically linked to a transboundary river or lake and that flow into a common terminus. They may also apply to transboundary aquifers that are hydraulically linked to an internal water body, so long as the interrelated surface and subsurface waters flow into a common terminus. All other aquifers are excluded from the Convention’s regime (for a more detailed analysis, see here).
UNWC, transboundary aquifers, and international law
While the UNWC is widely regarded as codifying customary international law, it draws almost exclusively from state practice related to the management and allocation of transboundary rivers and lakes. This perspective is understandable as the bilateral and multilateral cooperative experience over transboundary groundwater resources is scant in comparison. Nevertheless, many of the norms contained in the UNWC are equally (or, at least, similarly) applicable to transboundary aquifers.
A 2011 study suggests that the customary responsibilities most conspicuous in state practice include the substantive obligations of equitable and reasonable utilization and of no significant harm. The study also recognized the existence of accepted procedural duties, including: regular exchange of data and information, generation of supplemental data and information through continuous monitoring and related activities, and prior notification of planned activities. The latter obligation is considerably more general and less developed procedurally than what is contained in the UNWC. Principles contained in the UNWC, but which have yet to arise in state practice for transboundary aquifers, include norms related to ecosystem protection and pollution prevention, cooperative management mechanisms, and the settlement of disputes. In addition, the study identified groundwater-specific concepts that, while logical, have yet to emerge in state practice, including obligations related to protecting recharge and discharge zones.
In 2002, the UNGA tasked the UNILC with drafting principles of law for transboundary aquifers based on trends in state practice and customary norms. The resulting Draft Articles are now before the UNGA (see here). While the Draft Articles were modeled largely on the UNWC, there are a number of noteworthy differences. The UNWC applies to certain transboundary and some domestic aquifers as discussed above. In contrast, the Draft Articles apply to all transboundary aquifers, regardless of whether they are hydraulically linked to any other water body (surface or subsurface), and to domestic aquifers that are hydraulically related to a transboundary aquifer. In addition, the Draft Articles are tailored specifically for transboundary aquifers and include references and principles related to protecting recharge and discharge zones, ensuring the functioning of aquifers, and aquifer-related monitoring activities. If the Draft Articles proceed toward an independent legal instrument, which is yet uncertain (see here), the Draft Articles and UNWC will have to be harmonized.
The coming into force of the UNWC is a significant milestone in the evolution of international water law. While the Convention’s applicability to certain of the world’s groundwater resources may be limited, its growing acceptance and implementation signifies the global community’s broadening commitment to manage and utilize transboundary freshwater resources through peaceful and cooperative means. It also recognizes and affirms transboundary groundwater resources as a legitimate topic of international law.