Water Under the Bridge

In December 2024, China approved the construction of the Medog Hydropower Station on the Yarlung Tsangpo River in Tibet, which flows on to become the Brahmaputra in India and the Jamuna in Bangladesh. The project is set to be the world’s largest hydropower dam.

The Medog Project has raised concerns not just for the Tibetans, who will have to be resettled, but also for the lower riparian states, like Bangladesh and India, because the size of the project indicates that it could potentially choke or divert water flow. These concerns primarily arise out of the fact that China has not meaningfully declared its plans for the project to India and Bangladesh.

This article argues that China is bound, under customary international law, to duly notify and cooperate with its co-riparian states. To this end, it first analyses the obligation to notify co-riparians of planned use under customary watercourse law and goes on to argue that the project triggers this obligation. Finally, the article showcases China’s acceptance of this obligation in other contexts and proposes a cooperative path forward.

The Duty to Notify as Customary International Water Law

The 1997 UN Convention on the Law of the Non-Navigational Uses of International Watercourses (UN Watercourses Convention) is the key international instrument governing shared freshwater, to which China is not a state party. It is, however, widely accepted in scholarship on the Convention that, to the extent that it codifies the principles of ‘equitable and reasonable utilisation’ and the ‘no significant harm’ doctrine, the Convention reflects customary international law. This includes Article 11, which requires watercourse states to exchange information and consult on the ‘possible effects’ of planned measures.

Building on this principle, Article 12 of the Convention creates an obligation on watercourse states to provide timely notification and data before implementing any measure that may have a ‘significant adverse effect’ upon other watercourse states. The main objectives of such prior notification and consultation are ‘maintaining harmonious relations among watercourse states and preventing adverse transboundary damage’.

Historically, some states have argued that watercourse states have substantive obligations which constitute customary international law (as codified in Articles 5 and 6), whereas the procedural obligations (such as Articles 11 and 12) do not (see para. 90). However, the International Court of Justice in the 2022 Silala case held that the obligations to cooperate, notify, and consult complement the substantive customary obligations of every watercourse State (para. 110). In fact, it also specifically recognised Article 12 of the Convention to reflect customary international law (para. 118). Notably, the Court did not consider Article 11 to be custom (para. 111). This observation, however, has been considered to be based on little analysis and without regard to contrasting evidence (see p. 60).

With respect to the criteria for notification, the ILC’s Commentary to the Draft Articles on the Convention explicitly states that the threshold established by Article 12 of ‘significant adverse effects’ is intended to be lower than that of ‘significant harm’ under Article 7. Furthermore, the UN Special Rapporteur on the law of the non-navigational uses of international watercourses also clarified that Draft Article 11 (which included the current Article 12) ‘is couched in terms of appreciable harm in order to facilitate a joint determination of whether any harm entailed by the new use would be wrongful’.

Similar variations of the ‘adverse effect’ standard are established in other environmental treaties as well. For example, the Espoo Convention (Article 3), the Helsinki Convention (Article 6), and the SADC Protocol on Shared Watercourses (Article 4(1)) all contain similar obligations. A prior notification obligation is also imposed by many bilateral and multilateral treaties governing specific shared watercourses, such as the Indus River (Article 7(2)), Sava River (Article 4), and the Mekong Basin.

Why the Medog Project Triggers the Obligation to Notify

Whether a particular project meets the ‘significant adverse effect’ threshold is ultimately a question of fact. However, states must act diligently not only where there is evidence of actual harm, but also where there is a risk of such harm (see Pulp Mills, para. 205). This would allow a joint determination of the extent of the harm, facilitating cooperation, as well as equitable and reasonable use.

In fact, regional agreements like the Mekong River Commission’s procedural framework (to which China is a Dialogue Partner) and the Convention on the Sustainable Management of Lake Tanganyika explicitly recognise that construction and operation of large dams and similar infrastructure are activities that are likely to have significant adverse effects upon a shared basin (Annex I(A), entry 8).

As far as China’s own harm assessment is concerned, the spokesperson for China’s Ministry of Foreign Affairs has publicly stated that the Medog project ‘will not adversely affect downstream regions.’ In fact, China has cursorily declared that downstream states should not ‘read too much into [the project]’. However, it has not made any official meaningful declaration or justifications regarding the project’s expected scale and impact.

To the contrary, studies predict that if China diverts or controls the river’s flow, India could experience unpredictable floods during monsoon seasons and severe droughts in dry months. Keeping in mind that the Brahmaputra supports nearly 130 million people and six million hectares of agricultural land, such diversion would be especially challenging for India. Furthermore, 55 per cent of Bangladesh’s irrigation depends on the Jamuna. Thus, China’s unilateral construction could significantly endanger water security in Bangladesh, demonstrating the value of procedural obligations, like prior notification, in ensuring stability of water supply and agricultural production in a region.

China’s Acceptance of the Duty to Notify

China is not a party to the UN Watercourses Convention. In fact, it voted against the Convention’s adoption in 1997. However, this section demonstrates that it has not been a persistent objector to the rule of prior notification.

China expressed four reasons for its rejection of the Convention: (i) a lack of general agreement amongst participating states, (ii) the Convention’s failure to refer to the notion of sovereignty, (iii) a perceived imbalance between upstream and downstream states, and (iv) its opposition to mandatory dispute settlement mechanisms.

However, China has subsequently shown a significant inclination away from these objections, and towards the principles embodied by the Convention. For example, it has entered into bilateral and multilateral agreements based on the principles of equitable and reasonable use.

More crucially, China did not oppose the prior notification obligation during the preparation or adoption of the Convention. In fact, China has accepted the obligation of prior notification and consultation through its regional water-sharing agreements, including with Kazakhstan (Article 6), Mongolia (Article 3(2)), and Russia (Article 5). Even with respect to India and Bangladesh, China has signed Memorandums of Understanding (MoU) with them, recognising such an obligation, albeit non-binding.

Accordingly, the customary obligation to notify would be opposable to, and with that, binding on China (ILC Conclusions on Custom, Conclusion 15, paras. 6-9).

China’s Cooperation Through Regional Agreements

China is no stranger to regional agreements with respect to cooperation on water sharing. As a matter of fact, it refers to ‘cooperation’ right at the beginning of most of its international agreements, embracing it as a central principle across its treaty practice. For instance, its agreements with Mongolia (Articles 2, 3, and 5) and Kazakhstan (Article 5) enumerate activities in which the parties may cooperate, including monitoring, infrastructure maintenance, technology exchange, and joint research.

In keeping with this spirit of cooperation, China has previously codified an obligation to notify co-riparians regarding projects on a shared water source in several of its agreements: Article 17 of the Borderline Protocol between China and North Korea requires prior approval before changes to the channel of navigation or the construction of any installation on the boundary river are made. Similarly, Article 2 of the Provisional Agreement on the Handling of Border Affairs between China and Vietnam provides that ‘any project that would have [a] negative effect on boundary waters can be carried out only upon agreement by the two parties’.

Notably, China is also a Dialogue Partner to the Mekong River Commission (MRC), a platform for regional cooperation, created by Cambodia, Laos, Thailand, and Vietnam and tasked with implementing the 1995 Mekong Agreement. The Commission has published the Procedures for Notification, Prior Consultation and Agreement, which provide a detailed mechanism for ensuring transparency for projects using water from the Mekong basin which may significantly alter water flow or quality of the mainstream.

These procedures largely reflect the principles of Article 12 of the UN Watercourses Convention by requiring any water-use project to undergo either the process of notification, prior consultation or specific agreement by the state developing it. While the procedures are not binding on China, it has signed an agreement with the MRC in 2020 providing year-round hydrological data from Chinese stations at the Upper Mekong. Consequently, it has shown an inclination towards a transparency obligation with respect to planned use of shared watercourses.

Cooperation with Co-Riparians in the Brahmaputra Basin

The equitable and reasonable use of shared water resources requires, at the very least, sharing information and consultation over planned projects that could significantly affect other states. As discussed above, China, being a party to approximately fifty treaties and soft law instruments, which govern its transboundary waters, generally embraces cooperation as a key theme across its treaty obligations.

However, India and Bangladesh are the only co-riparian states with whom China does not share any mutual cooperative agreements. Even the MoU China does have with them tends to get suspended unilaterally during times of conflict or political tension (for example, China’s suspension of its MoU with India after the Doklam Standoff in 2017). In order to comply with its customary obligations, China would, however, benefit from entering into a joint mutual cooperation agreement with these two states.

A regional framework that concretely codifies the principles of equitable and reasonable sharing, no significant harm, and transparency would help to stabilise the equation between the three states with regard to water sharing in the Brahmaputra basin. The most ideal template for such a regional cooperation model would be the MRC and its extensive procedural rules for prior notification. Moreover, China’s existing agreements with Russia, Kazakhstan, and Mongolia may be models, as they provide for reliable information exchange, joint monitoring, environmental cooperation, flood preparedness, and joint scientific research.

Conclusion

China’s decision not to sign the UN Watercourses Convention does not release it from the duty to notify. The Convention continues to protect co-riparian states by codifying a customary obligation of prior notification. This obligates China to meaningfully respond to India and Bangladesh’s requests for exchange of data, given the Medog project’s potential to ‘disrupt the Brahmaputra’s natural flooding cycle’ and threaten the fertility of India and Bangladesh’s floodplains.

China has already accepted this obligation from both ends: as a downstream state in its agreement with Mongolia, and as an upstream state with Kazakhstan. Thus, apart from political considerations or domestic imperatives, there is no legal reason for the Brahmaputra to be treated as an exception. Therefore, a mutual cooperation framework with India and Bangladesh, modelled on the MRC’s procedural rules or on China’s own bilateral agreements, would allow China to discharge its obligations under customary watercourse law and afford some security to the 130 million people for whom the Brahmaputra basin is a primary source of water.

This article was written during my time as a Research Assistant for the Centre for Water, Ocean Governance and Sustainability Law, at Jindal Global Law School. I am grateful to Prof. (Dr) Tony George Puthucherril and Sarthak Sahoo for their guidance and comments on the original draft.