Across the world, nations sharing transboundary rivers face persistent geopolitical risks over water allocation and weaponization. Nowhere, however, are these risks more pressing than on the foothills of the Himalayas. Two recent and headline-grabbing disputes are China’s proposal to dam the Yarlung Tsangpo River, which took another step forward last week, and India’s suspension of the Indus River Treaty.
While coverage of these recent crises has focused on water weaponization, an arms race in dam-building, and ecological disruption, it has failed to anchor these conflicts in their rightful legal context. Commentators, by and large, are overlooking a long history of international lawmaking aiming to install certainty and security over the use of transboundary rivers. The recent conflicts in the Himalayas should serve as impetus for countries to strengthen this existing international regime, rather than repudiate it.
The centerpiece of the general international law governing transboundary rivers is the 1997 Convention on the Law of the Non-navigational Uses of International Watercourses (the U.N. Watercourses Convention or Convention). At its heart, it espouses the twin principles of “equitable utilization” (Article 5) and “cause-no-harm” (Article 7). As discussed below, both arguably reflect customary international law today.
Moreover, since 2023, three new countries – Gambia, Zimbabwe, and Kazakhstan – ratified the Convention, signaling increasing momentum. And even as non-signatories, the United States and its partners should seize this opportunity to strengthen the international governance of transboundary rivers, clarify default international legal rules, and chart a more stable and secure water future.
The Himalayan Disputes and the Shortcomings of the Operating Legal Architecture
Two broad categories of international law govern the sharing of transboundary rivers: river basin treaties and blanket international law principles. The U.N. Watercourses Convention codifies the latter.
The former category, made up of over 400 river basin treaties signed since 1820, forms the bulk of the current international legal architecture. Typically, these are practical treaties negotiated by parties living in and/or with legal authority over those river basins. They are sensitive to local economic, cultural, and geographic factors. Many of these treaties have withstood the test of time. However, reliance on fragmented treaties leaves some countries and communities unprotected and others uncertain. The recent Himalayan crises highlights these shortcomings.
River basin treaties do not cover all shared rivers – not even all major ones. No treaty, for example, governs the Yarlung Tsangpo, which flows from Tibet into India and Bangladesh as the Brahmaputra-Jamuna. In December 2024, China announced a plan to build the world’s largest hydroelectric dam on the Yarlung Tsangpo; the country began construction earlier this month. India vehemently protested China’s proposal, asserting environmental concerns and security worries. Indian Ministry of External Affairs Spokesperson Randhir Jaiswal cautioned China against weaponizing the dam – whether to stop the flow or to cause a flood – in times of conflict. The protest was largely rhetorical and diplomatic, however, rather than legal: India, however, could not point to a river basin treaty that legally limits China’s usage of the Yarlung Tsangpo or prohibits the building of the dam.
Crucially, parties, especially upstream nations, often face few impediments against leaving existing river basin treaties unilaterally and at whim. For example, India unilaterally suspended the Indo-Pakistan Indus Waters Treaty following the Apr. 22, 2025, terrorist attack near Pahalgam, even before the attack could be independently attributed to Pakistan. On paper, India claimed that the treaty contained no prohibition against such a “suspension” or “abeyance” On the ground, India immediately vowed to slash the Indus River’s water supply to Pakistan and did indeed close several dams on the Indus to restrict the river’s flow. India did so despite the fact that 80 percent of Pakistan’s agriculture depends on the Indus River. Eventually, this course of events precipitated a short military clash. Although fighting has since stopped, the underlying conflict remains unresolved. The demise of the Indus Waters Treaty fueled regional instability and highlighted the fragility of the current international legal architecture.
Despite these shortcomings, the international community should aim not to displace river basin treaties, but to buttress them with robust backstops in the form of blanket international law instruments – in other words: forge clear, equitable, and reliable default rules. These default rules should have the authority to govern and resolve disputes in the absence of an existing treaty or in the event of a treaty failure.
The Emergence of the U.N. Watercourses Convention
The U.N. Watercourses Convention codifies many such default rules through decades of legal development and negotiations. Beginning in the 1950s, lawmakers began searching for general international law principles to govern transboundary rivers. In 1957, France and Spain engaged in an arbitration over the diversions of water from Lake Lanoux, a part of a transboundary riparian system on the Pyrenes. In their decision, the arbitration panel conceded that “[c]ustomary international law” did not yet supply “a general principle of law” to allocate cross-border water resources at the time. In reaching this concession, the panel scourged various traditional sources of law, including the system of compascuités local to the Pyrenes. The panel remarked that the compascuités, which once administered communal water rights in the region, symbolized a “spirit of co-operation and of understanding.”
Ten years later, lawmakers launched a more concerted effort to codify that spirit through an international legal document. In 1967, the International Law Association adopted the Helsinki Rules on the Use of the Waters of International Rivers (the Helsinki Rules). Article IV of the Helsinki Rules recognizes a right to “a reasonable and equitable share in the beneficial uses of the waters” for all “basin States.”
Although the U.N. did not officially endorse the Helsinki Rules, it embraced many of Helsinki’s ideals in the Watercourses Convention 30 years later. Article 5 of the Convention directly borrows Helsinki Article IV’s principle of “equitable utilization.” At the same time, the Convention also elevates one of Helsinki’s more circumspect ideas to new heights: Article 7 of the Convention calls for states to “take all appropriate measures to prevent the causing of significant harm to other watercourse States.” The “cause-no-harm” principle, a mere balancing factor in Helsinki, becomes a core tenet in the Convention.
Unlike the Helsinki Rules, the Convention is legally binding. Having lain dormant for 17 years, it finally entered into force on Aug. 17, 2014, when Vietnam ratified as the 35th State. Since then, five more countries have ratified the Convention to reach 40 in total. As noted above, three of these countries ratified after 2023 in a recent wave.
Despite these promising developments, courts and scholars still debate the Convention’s strengths, prospects, and scopes in reflecting customary international law, which encompasses only “general and consistent practice of states [rooted in] a sense of legal obligation.” Stephen McCaffrey, the U.N. International Law Commission’s special rapporteur in preparation for the Convention, argues that three provisions from the Convention – equitable utilization, cause-no-harm, and notification of planned measures to other watercourse states (Article 12) – best mirror such customary practices.
Phantom Contradictions: “Equitable Utilization” and “Cause-No-Harm”
The juxtaposition of “equitable utilization” and “cause-no-harm” as co-equal principles of the Convention has become a source of tension. Scholars contend that they are inherently contradictory: whereas “equitable utilization” signifies a permissive stance towards river uses, “cause-no-harm” chills exploitation. The former guarantees each nation’s right to tap the river flow for development, but the latter exposes those very developments to liability.
This contradiction suggests that customary international law regarding transboundary rivers is still evolving and lacks clear consensus. At the same time, it offers valuable insights into how international courts might reconcile and integrate the various principles embodied in the Convention.
A 2022 International Court of Justice (ICJ) judgment in Chile v. Bolivia offers one of the most recent analyses of the Convention’s scopes and mandates. The case arose from Chile’s complaint of Bolivia’s exploitation of the headwaters of the Silala River. While neither country is a signatory of the Convention, Chile nevertheless challenged Bolivia’s upstream uses of the river (as well as the connected wetlands) on both “equitable utilization” and “cause-no-harm” grounds, regarding both provisions as general principles of customary international law.
During the course of the ICJ proceedings, however, the positions of Chile and Bolivia gradually converged. On the question of “equitable utilization,” both countries came to the agreement that the right to equitably exploit the river considers historical practices and does not mandate compensation for past uses. On the question of “cause-no-harm,” the parties reached a consensus that it pertains only to “significant harms,” and does not dictate every aspect of how nations could use transboundary rivers. While the ICJ broadly recognized the applicability of Article 5 and 7 of the Convention as customary international law, it declined to specify concrete permissible future uses nor “in any way freeze further development.”
The ICJ’s permissive, reconciliatory reading of the Convention alleviates the document’s inherent tension and reorients its mandates. Today, the Convention would likely come up short in adjudicating small transgressions. At the same time, it is well positioned as a bulwark against the most egregious unilateral violations of water rights on the international stage. The latter is exactly what the international community needs at this moment.
Both Himalayan crises represent egregious violations of the spirit of the Convention. China could claim neither equitable nor historical uses in its decision to dam the sparsely-populated headwaters of the Yarlung Tsangpo, which feeds the densely-populated downstream. India’s unilateral suspension of the Indus Water Treaty, threatening 80 percent of Pakistan’s agriculture, was likewise an unambiguous violation of the principle of “cause-no-harm.” Even though neither China nor India are signatories, under the ICJ’s conception, the Convention nevertheless provides the requisite legal bases to resist their unilateral behaviors. Thus, the Convention should be read as outlining baseline expectations of how nations should govern transboundary rivers.
Realizing the Promises of the U.N. Watercourses Convention
States could best promote water security and minimize geopolitical risk by reading the Convention as such: a baseline expectation for all nations to follow. This would allow all signatory and non-signatory countries to appeal to the Convention’s basic principles when confronted with significant river basin crises, such as those from the foothills of the Himalayas.
The United States, in particular, should embrace this reconciliatory reading of the Convention’s two guiding principles even if it does not ratify the Convention in the short term. Recognizing that the principles of “equitable utilization” and “cause-no-harm” are broadly applicable to signatory and non-signatory countries alike, the United States could reposition these more centrally in its rhetoric and advocacy. Despite favoring overall withdrawal from international commitments, the current administration could nevertheless recognize the applicability of these principles to achieve specific, narrow, and concrete policy objectives.
Endorsing these principles would strengthen American diplomacy. President Donald Trump has claimed credit for brokering the ceasefire between India and Pakistan. Anchoring the peace in the Convention would shore up this important American diplomatic victory. It would incentivize both India and Pakistan to restore the Indus River Treaty or otherwise forge a new, sustainable resolution, at America’s behest.
Endorsing the Convention’s two core principles would also expand American alliances in a contested region of the world. Today, the United States and China are locked in a struggle for influence in Southeast Asia. More than ever before, Southeast Asian countries feel the pressure to choose between the two major powers on trade, military, and development. Promoting the core principles, including the use of the Convention where it applies, would better align America’s position with key Southeast Asian nations downstream from China, including Vietnam, India, Bangladesh, and Thailand, on a critical issue for these countries. Strengthening recognition of “equitable utilization” and “cause-no-harm” as broadly-applicable principles of international law would erode China’s ability to unilaterally leverage the major Asiatic rivers that originate from the Tibetan Plateau (the Mekong, the Salween, and the Brahmaputra, to name a few) for geopolitical clout, forcing China to negotiate as an equal party.
Lastly, adopting the ICJ’s conception of the Convention’s principles – including in dispute resolution between non-signatory countries, as in Chile v. Bolivia – as a baseline may shield U.S. interests from future volatility. The United States is currently facing renegotiations over some of its most important river basin treaties, including treaties over the Columbia and Colorado rivers. Regarding the Columbia River Treaty, many Americans are worried that the upper-riparian Canada might pull out of the treaty due to recent tensions. Others fear that their longstanding water rights might be traded away as a bargaining chip in a broader negotiation. The current administration may assuage these worries by embracing the Convention’s principles as baseline guarantees. It could credibly promise, to the American communities living in those river basins, that their basic water rights would be secure no matter how the renegotiations turn out. At least, recognizing these baseline principles reduces one point of uncertainty in the turbulent trade negotiations between the United States and its neighbors.
In the United States and elsewhere, when old river basin treaties have run their course, and until new treaties are made, the U.N. Watercourses Convention offers the best chance to secure the water futures for all who rely on the world’s fragile, life-giving transboundary rivers.
