Archive for August, 2014

Richard Paisley and Taylor Henshaw: The 1997 UN Watercourses Convention from a North American Perspective

Sunday, August 24th, 2014

The following post by Richard Paisley and Taylor Henshaw is the tenth and final essay in the series related to the entering into force of the 1997 UN Watercourses Convention (see links to all of the essays here). Messrs. Paisley and Henshaw are with the Global Transboundary International Waters Governance Initiative at the University of British Columbia in Vancouver, Canada, which Mr. Paisley directs. Mr. Paisley can be reached at: rpaisley [at]


The nations of North America—Canada, Mexico and the United States (USA)—share a significant number of international drainage basins and transboundary aquifers, comprising 16% of the world’s transboundary river basins. The three countries have entered into various bilateral agreements with their neighbors for the management and allocation of their transboundary waters. However, while each voted in favor of the UN Watercourses Convention (UNWC) when it came before the UN General Assembly, none of them has ratified the instrument. The objective of this essay is to critically consider the absence of these three nations from the roll of the UNWC and to assess whether ratifying and implementing the UNWC would be in the individual and collective best interest of all three countries.

International Freshwater Drainage Basins of North America. Source: UN Watercourses Convention Online Users Guide


The three nations appear to be in no great rush to ratify and implement the UNWC. This may be due to a perception that their international drainage basins are sufficiently managed without the UNWC: long-standing bilateral institutions have been established to deal with various aspects of the conservation and management of international drainage basins in North America.

Prominent among these mechanisms are the International Joint Commission (IJC) between Canada and the USA, and the International Boundary and Water Commission (IBWC) between Mexico and the USA. The history and practice of the IJC and the IBWC provide a rich body of work to review that falls beyond the scope of this essay. Nevertheless, it is pertinent to mention some of the challenges the two commissions face, such as: managing significant risks to water quality and quantity; the linking of border environments to binational trade and associated agreements; new stresses on public health and national economies; changes due to population growth and industrialization; greater demands on shared resources; increasing emphasis on public and indigenous peoples participation in decision-making; greater value placed on non-traditional water uses, such as “in stream” flows; and the imperative to establish ecosystem and active adaptive management approaches to resource management.

In addition, both institutions have experienced recent changes to their constituencies with the increasing influence of environmentalists and economic, social justice, and sustainable development advocates. As a result, ratification and implementation of the UNWC could help make both the IJC and the IBWC more relevant by increasing the focus on, and energy devoted to, the more sustainable conservation and management of transboundary waters and related resources in all three countries.

Substantive Objections

Whether and the extent to which Canada, Mexico and the USA have substantive objections to the UNWC is not well known. This may be because such objections are masked by the fact that all three countries were among, not just the 103 countries who voted in favor of the UNWC, but also the 38 countries to officially sponsor the UNWC.

On reflection, various substantive reasons may exist to explain why all three countries are not overly anxious to ratify and implement the UNWC. Mexico provides a good example. On the one hand, Mexico probably favors the UNWC, in part, because the Convention provides a basis for cooperating over measures to prevent, reduce and control pollution, including from the USA, which is an issue of great sensitivity to Mexicans. On the other hand, groundwater is tremendously important for Mexico where many believe that the conservation and management of shared transboundary aquifers necessitates a different international legal regime to that presented in the UNWC. More specifically, Mexico could be disinclined to ratify and implement the UNWC until more clarity is provided regarding the relationship between the UNWC and the emerging Draft Articles on the Law of Transboundary Aquifers. According to Stephen McCaffrey, such clarity, regrettably, may be a long way off and:

will crucially depend on eliminating both the overlap between the draft and the UN Convention in terms of the physical subject matter they regulate, and the notion of “sovereignty” over shared groundwater, which should have no place in any set of rules governing the use, protection, and management of shared freshwater resources.

Constitutional Politics

At the political level, the ratification and implementation of international treaties has become an increasingly challenging undertaking in all three countries.

In Canada, the negotiation, signing and ratification of international treaties is controlled by the executive branch of the federal government. However, many international treaties, such as the UNWC, deal with matters that fall under the provincial sphere of legislative jurisdiction pursuant to the division of powers in Canada between the federal government, the provincial governments and First Nations (sections 91, 92, 92A and 35 of the Canadian Constitution).  Also, according to Professor Emeritus of Economics and Forestry at the University of British Columbia, Peter Pearse:

A recurrent question in discussions about water management in Canada is “What is the role of the federal government?”  A stranger to these discussions might think, naively, that this is simply a constitutional question.  But even a good constitutional lawyer can not give a crisp answer.  To some extent the question is a political one – “What does the federal government think its role is, at the moment?”  This changes.

As a practical matter this means that ratification and implementation of the UNWC in Canada would likely trigger challenging and hard-nosed fiscal and other negotiations among the federal, provincial and First Nations levels of government. An analogous situation occurred when Canada was asked to ratify and implement the Espoo Convention on Environmental Impact Assessment in a Transboundary Context.

In the USA, the legal situation regarding international treaties is somewhat different, but possibly even more challenging. Under United States constitutional law, an international “treaty” is an agreement that has received the “advice and consent” of two-thirds of the United States Senate and has been ratified by the President (see here). As a practical matter, given the increasing political polarization within the United States Senate, obtaining the consent of two thirds of Senate members for any multilateral treaty, including the UNWC, would be exceedingly challenging.

Mexico is much closer to Canada constitutionally than to the USA as Mexico constitutionally allocates separate and exclusive spheres of authority to the states/provinces and the federal government. International treaties must conform to the Mexican Constitution in order to be valid. However, many international treaties address topics that in Mexico fall within the exclusive authority of the states/provinces. Seemingly, in practical terms this means that Mexico may need to enact domestic legislation to transform international treaty obligations into enforceable domestic law, which could be both time consuming and expensive.


Another reason why the UNWC has not yet been ratified and implemented in Canada, Mexico and the USA is the paucity of champions at the political level in all three countries. This resonates with Nicolo Machiavelli’s observation:

there is nothing more difficult to take in hand, more perilous to conduct, or more uncertain in its success, than to take the lead in the introduction of a new order of things. Because the innovator has for enemies all those who have done well under the old conditions, and lukewarm defenders in those who may do well under the new. This coolness arises partly from fear of the opponents, who have the laws on their side, and partly from the incredulity of men, who do not readily believe in new things until they have had a long experience of them.

Justifying the UNWC in North America

Despite the apparent obstacles noted above, there are at least three compelling reasons why Canada, Mexico and the USA should immediately ratify and implement the UNWC. First, ratification and implementation will send a strong and important message to each other, and to the world community, generally, that sovereign states have important rights and responsibilities when it comes to transboundary freshwater resources.

Second, the fact that Canada and the USA are variously both upstream and downstream of each other and that the USA is upstream of Mexico, will particularly and importantly help dispel any lingering misperception that the UNWC may be biased in favour of downstream or upstream states.

Third, Canadian, Mexican and American support for the Convention could not be more timely given how the world community is currently struggling with the harsh realities of climate change and water scarcity.

Ratifying and implementing the UNWC in North America would also demonstrate a wider acceptance of practice under the Convention as representing customary international law. In turn this could place the UNWC higher on various political agendas and could help lead to a more stable framework for transboundary water cooperation globally.


Dr. Maria Querol: The UN Watercourses Convention and South America

Thursday, August 21st, 2014

The following post by Dr. Maria Querol is the ninth 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). Dr. Querol is an international law consultant with a vast background in international water law. She can be reached at maria.querol [at]



Although the 1997 UN Watercourses Convention (UNWC) has finally entered into force, not one South American country is among its State Parties. Whilst Brazil, Chile, Uruguay and Venezuela voted in favour of its adoption at the UN General Assembly (UNGA), Argentina, Bolivia, Colombia, Ecuador, Paraguay and Peru all abstained. Paraguay and Venezuela were the only states from the region to sign the Convention, in 1997 and 1998 respectively. Nevertheless, neither has made any attempt to ratify it.

Many arguments have been presented to justify this flagrant absence, mainly focusing on the concern of South American states regarding challenges to their sovereignty over water resources flowing through their territories. However, this is not the only factor to be considered when analysing the region’s position on this topic.

Multilateral transboundary water treaties of South America

South American states have a history of concluding international treaties to regulate the management of their shared watercourses. This long-standing tradition favors the implementation of specific mechanisms and international water law norms over more general regimes. While most of these agreements are bilateral, there are four exceptions: the 1969 Treaty of the River Plate Basin, the 2010 Guarani Aquifer Agreement, the 1978 Amazon Cooperation Treaty, and the 1995 Agreement constituting the Tri-National Commission of the Pilcomayo River Basin.

International Basins of South AmericaThe Plate Basin Treaty entered into force for Argentina, Bolivia, Brazil, Uruguay and Paraguay on 14 August 1970.  It operates as an umbrella for other more specific agreements, both bilateral and multilateral, that have been concluded with regard to particular transboundary watercourses within the basin. Article VI of this agreement foresees the possibility that its Contracting Parties may conclude specific, partial, bilateral, or multilateral agreements designed to develop the basin. Accordingly, the Guarani Aquifer Agreement was concluded within the framework of the Plate Basin Treaty. Thus, the basin is regulated with an intergrated approach, both from a general and a more specific standpoint.

Transboundary watercourses are regarded in the region as shared natural resources. This view was particulary emphasized by both Argentina and Uruguay in the 1975 River Uruguay Statute and reaffirmed in 2010 in the Pulp Mills case before the International Court of Justice (ICJ). In this regard, Argentina argued in its memorial to the Court that “[t]he shared nature of the River Uruguay is also apparent from the fact that obligations are imposed on Argentina and Uruguay at an international level. The 1975 River Uruguay Statute is actually a repository for th[ose] international obligations”. Those obligations comprise the rules of no significant harm, equitable and reasonable use, and prior notification. It is important to bear in mind that these general norms are only applicable to the use and protection of shared natural resources as long as the states sharing the resource have not implemented a more specific conventional regime. Accordingly, Argentina also declared that while the River Uruguay Statute had been concluded 22 years before the UNWC was adopted by the UNGA, “the Statute provides for the establishment of a system of co-operation which is far more rigorous than that laid down by the Convention.”

The Amazon Cooperation Treaty was adopted by Bolivia, Brasil, Colombia, Ecuador, Perú, Suriname and Venenzuela to promote equitable and mutually beneficial results in the Amazon territories under their respective jurisdictions. It entered into force on 12 August 1980. The no harm rule and the reasonable and equitable principle are enshrined in Article I of the agreement. The no harm rule is also implicit in Article XVI as it stipulates that the decisions and commitments adopted by the State Parties to the treaty shall not be to the detriment of projects and undertakings executed within their natural territories, in accordance with international law. In addition, Article V prescribes the rational utilization of the water resources of the Amazon System. Periodic exchange of information among all the State Parties is also provided for in Articles I, VII and XI.

By virtue of an amendment to Article XXII of the Amazon Cooperation Treaty, the Organization of the Treaty of Amazon Cooperation was created with the view of further strengthening and ensuring the more effective implementation of the goals of the Treaty. The existence of an international legal entity directly regulated by public international law no doubt facilitates the realization of projects and can provide guidance for the rational utilization and sustainable management of shared water resources in the Amazon region.

Although the Amazon Cooperation Treaty does not prescribe a dispute resolution mechanism, State Parties can agree to submit their disputes to an arbitral tribunal or a permanent judicial organ such as the ICJ. They can also resort to a political dispute resolution method such as mediation or good offices. In any case, states are always bound by the customary obligation to negotiate a solution to their disputes in good faith.

Transboundary water management in South America

Unlike the practice in other regions of the world, discussions over shared water resources in South America, more often than not, take place under a cordial atmosphere. Although information exchange among states does take place in the region, the necessary data may be scattered around in different institutions, in which case its collection can prove quite burdensome. With reference to dispute resolution, South American states have been resolving their issues through direct negotiations and in some cases, as between Argentina and Uruguay, through the ICJ. Whilst progress has been made in terms of cooperation and knowledge over the management of shared surface water resources, this is not the case with regards to all shared groundwater. A first step forward has indeed been taken with regards to the Guarani Aquifer. But, further in-depth knowledge is necessary to provide a more complete scenario of all the possible consequences of human action related to transboundary groundwater resources.

Currently, South American states do not appear to have an immediate interest in a universal framework treaty to regulate the management of their transboundary water resources. Rather, they would prefer to continue resorting to their existing bilateral and multilateral agreements and to applicable customary norms in the absence of such treaties. They even count on international organizations to help implement their preferred management regime in the case of the Amazon Basin, and through a framework agreement for the Plate Basin.

This does not mean that the UNWC will have no value to South America. To the extent that the Convention codifies general international rules, its norms are binding on all states of the international community, including those of South America. In addition, the entry into force of the UNWC might foster the development of new customary norms in areas not yet covered by the existing regional treaties and could prove very influential in the interpretation of those particular treaties.


Robyn Stein and Georgina Mackenzie: Implication of the Entry Into Force of the UN Watercourses Convention for Southern African States

Tuesday, August 12th, 2014

The following post by Robyn Stein and Georgina Mackenzie is the eighth 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). Ms. Stein is Director and attorney with Edward Nathan Sonnenberg, Inc. in South Africa where she specializes in water law and policy. She can be reached at rstein [at] Ms. Mackenzie is a candidate attorney working with Ms. Stein.


The Revised Protocol on Shared Watercourses (Protocol) of the Southern African Development Community (SADC) came into force in 2003. The original Protocol, concluded between SADC member states in 1995, was revised to ensure that it reflected those of the then pending 1997 UN Watercourses Convention (UNWC). With a few notable exceptions, numerous provisions of the Revised Protocol have identical counterparts in the UNWC. As South Africa and Namibia are the only SADC states to have ratified the UNWC, it must be asked whether the entry into force of the UNWC will have any impact on the implementation or content of the SADC Protocol, and whether other SADC states might now be motivated to accede to the Convention.

Notable differences between the UNWC and the Protocol

Despite numerous Protocol provisions mirroring the UNWC, there are two fundamental differences between the instruments:

Dispute resolution mechanisms

Under Article 7 of the Protocol, member states must “strive to resolve” disputes relating to the implementation, interpretation or application of the Protocol amicably.  Otherwise, disputes must be referred to the SADC Tribunal. In contrast, the corresponding article in the UNWC, Article 33, offers numerous dispute settlement options beginning with negotiations, followed by mediation or conciliation through a third party, the use of joint watercourse institutions, submission to arbitration, and adjudication by the International Court of Justice.

Furthermore, under Article 33(3) of the UNWC, if the parties have not settled their dispute within 6 months, any party can unilaterally initiate impartial and compulsory fact-finding procedures. A “Fact-finding Commission,” comprised of members nominated by both parties, is thereafter required to produce a report setting out findings and recommendation for an equitable solution. While the parties must consider such findings and recommendations in good faith, scholars suggest that they are not bound by the pronouncement. In this sense, the Commission may be characterized as “compulsory conciliation.” This fact-finding procedure is one of the significant provisions of the UNWC, and yet the most notable absence from the Protocol.

Countries in the Southern African Development Community

“Equitable utilisation” principle vs the “no harm” obligation

Both the UNWC and the Protocol oblige watercourse states to utilise shared watercourses in an “equitable and reasonable manner” vis-à-vis other riparians. Whether or not such use is reasonable and equitable depends on a non-exhaustive number of social, economic and environmental factors listed in both instruments. Each instrument (Protocol Article 3(10)(a); UNWC Article 7(1)) obliges parties to take “all appropriate measures to prevent significant harm to other watercourse states.” The legal relationship between these two principles is of extreme importance and the precedence of one specific principle over the other has been deemed to have wide-ranging implications.

It is now widely recognised that the UNWC gives precedence to the equitable utilisation principle over the no significant harm obligation and is considered the “cornerstone” of the UNWC. This position is evident in the International Court of Justice’s endorsement of this preference in the 1997 case of Gabcikovo-Nagymaros. In contrast, Protocol Article 3(10)(b) states that where significant harm is nonetheless caused to another watercourse state, the responsible state must take appropriate measures to eliminate or mitigate such harm having due regard for the provisions of Article 3(10)(a), which embodies the Protocol’s no-harm obligation. Therefore some have interpreted the Protocol to give preference to the no-harm obligation over the equitable utilisation principle.

While it may be argued that some Protocol provisions have been poorly drafted, two arguments support the precedence of the no-harm obligation in the Protocol.

Despite the express reference to the UNWC, the Protocol was never intended to mirror the UNWC. This is evident in historical drafts and instruments as well as other notable differences between the two instruments. Moreover, while the Protocol provides a substantial definition for “significant harm,” the UNWC contains no comparable characterization. Arguably, inclusion of this definition in the Protocol indicates that the drafters intended to harness the objective nature of this definition and its factual importance to the complex set of SADC transboundary water resource issues. As such, they sought to ensure that the no-harm obligation prevails over equitable and reasonable use.

Stephen McCaffrey, a leading scholar of international water law contends that the preference in the Protocol for the no-harm obligation prevents SADC states from developing or using shared watercourses in a manner that causes significant harm to other watercourse states – even if such use or development were equitable and reasonable – unless the latter states consent to such use and development. While this precedence in the Protocol favours downstream watercourse states, the UNWC’s structure has the converse effect.

Accession to the UNWC by other SADC member states

As the Protocol is largely based on the framework of the UNWC, more SADC states might have been expected to have ratified the Convention by now. However, only Namibia and South Africa joined the UNWC. Two reasons might explain the hesitancy of remaining SADC states toward the Convention.

Questioning the relevance of the UNWC

Article 3(1) ensures that pre-existing watercourse agreements and states’ rights and duties arising from such agreements (including the Protocol) remain unaffected by accession to the UNWC. All that the Convention requires is that states “consider harmonizing such agreements with the basic principles” of the UNWC. Furthermore, Article 33(1) gives precedence to regional machinery where it exists (such as the Protocol) for dispute resolution. Therefore SADC states may feel that there is no urgency to accede to the UNWC.

Redundancy of instruments

The UNWC was intentionally designed as a framework convention with basic principles and rules that can be used flexibly and inform inter-state watercourse agreements. It was always intended to be supplemented by more detailed agreements. The Protocol, with its connection to the UNWC, adopted a similar framework approach. Therefore, some SADC states might view the UNWC as a duplication of the Protocol and regard membership in the Convention a redundant undertaking (see here).

Effect of entry into force of the UNWC on implementation of the Protocol

The origins of the UNWC reinforce one of the UNWC’s primary purposes – to codify and progressively develop the content of customary international water law. McCaffrey asserts that the UNWC strengthens and clarifies customary international law principles governing international watercourses through its status as the most authoritative statement of the norms of international water law, including the principle of equitable and reasonable utilization. SADC states opposed to the precedence of the no-harm obligation in the Protocol might use the UNWC to evidence customary international law’s preference for equitable and reasonable use. This could create discord among SADC members and cause undermine the founding principles of both the UNWC and the Protocol.

In contrast, SADC states that support the preference for the no-harm obligation in the Protocol might contend that the UNWC merely codifies the normative principles of customary international law without defining the core and content of the prioritisation of equitable and reasonable use over the no-harm obligation. At issue is the extent to which the UNWC provides practicable guidance on how the precedence will inform the drafting of effective shared watercourse agreements between states. Similarly, SADC members may assert that notwithstanding the precedence of equitable and reasonable use in the UNWC, alignment between the Protocol and the UNWC is unachievable until the UNWC offers more guidance on how its normative principles can be given practical effect (see here). This is particularly evident where competing interests arise in circumstances of hydro-political conflict and dire water scarcity, both of which are ongoing challenges within the SADC region.

This argument is reinforced by the nature of the UNWC as a framework instrument designed to inform the structure of local and regional watercourse agreements. By allowing pre-existing agreements to remain intact (Article 3(1)) and permitting adjustments to Convention provisions where required by local circumstances (Article 3(5)), the UNWC can be tailored to specific watercourses. This feature, however, may make some SADC states uncomfortable with the extent to which member states can depart from the UNWC’s norms, and the degree to which such departures and varied interpretations can be effectively managed.


Until more SADC states accede to the UNWC (which appears unlikely in the near future), the coming into force of the Convention will have limited effect on the Protocol. The UNWC will provide interpretive guidance to those Protocol provisions that incorporate the normative principles of customary international law embodied in the UNWC. Absent constructive and inclusive engagements between SADC states and a central agency responsible for managing and implementing the UNWC, it is unlikely that it that UNWC will have a tangible influence on the Protocol for some time to come.


Professor Gabriel Eckstein: Implications of the UN Watercourses Convention for Groundwater Resources

Tuesday, August 5th, 2014

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]   or   gabrieleckstein [at]

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).

Transboundary Aquifers of the World - 2012 Source: International Groundwater Resources Assessment Centre (

Transboundary Aquifers of the World – 2012
Source: International Groundwater Resources Assessment Centre



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.

Model of a Transboundary Aquifer Model, from Puri,, "Internationally shared aquifer resources management, their significance and sustainable management: A framework document," IHP-VI International Hydrological Programme Non-Serial Publications in Hydrology SC-2001/WS/40 (UNESCO 2001)

Model of a Transboundary Aquifer
Source: Puri,, “Internationally Shared (Transboundary) Aquifer Resources Management: Their Significance and Sustainable Management – A framework document,” IHP-VI International Hydrological Programme Non-Serial Publications in Hydrology SC-2001/WS/40 (UNESCO 2001)



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.