Transboundary water conflicts, cooperation, and pathways forward

When Water Becomes a Weapon: In early 2025, escalating tensions between India and Pakistan caused an armed conflict between the two countries. In a bold move that shocked regional observers, India announced its suspension of the Indus Waters Treaty (1) and threatened to halt or curb flows to Pakistan. Soon after, India reportedly flushed large volumes of water from upstream reservoirs and reduced releases into key tributaries. Such actions were viewed by Pakistan as an existential threat (2), since its irrigated agriculture and food security depend heavily on water from India (3). Officials warned that interference with cross-border water flows is an act of aggression. This episode is a vivid, contemporary example of how transboundary waters can be leveraged as strategic tools in geopolitical disputes, underscoring the fragility of long-standing agreements under heightened political stress (4, 5).

Transboundary river basins sustain over 50% of the world’s population, delivering water for agriculture, energy, ecosystems, and livelihoods (6). Codevelopment of solutions, driven by inclusive science diplomacy, is essential in these biophysically linked, geopolitically important landscapes. This approach combines rigorous research, stakeholder engagement, and iterative policy development. A prominent initiative exemplifying this is the PEER2PEER program, coled by the US National Academies of Sciences, Engineering, and Medicine, University of California Irvine (UCI), and Oklahoma State University (OSU), with support from the US NSF AccelNet program. PEER2PEER was established in 2021 to bring scientists and decision makers together in a “network-of-networks” in the water–climate domain to engage in formal dialogue on vulnerabilities in transboundary basins (Fig. 1). The aim is to enhance the capacity of governments, civil society groups, and nongovernmental entities to develop resilience against these vulnerabilities, defined as the ability to withstand and recover from disruptions caused by climate change, economic and population growth, and other stressors. Furthermore, PEER2PEER fosters international convergence research centered on transboundary water security in Africa, Central Asia, and the Middle East. It brings together existing networks from former and current National Academies of Sciences, Engineering, and Medicine programs, including the Partnership for Enhanced Engagement in Research (PEER) program and the Regional Frontiers programs in the Arab region and the African continent (7).

Fig. 1.

The PEER2PEER network science team and participants involved with transboundary water research. Image Credit: Sofia Bowman, National Academies of Sciences, Engineering, and Medicine.

Transboundary water challenges are found across the world, where external shocks, including political, climatic, or infrastructural, impede effective water governance and cooperation (8, 9). Examples include the Amu Darya Basin in Afghanistan, where water diversions through development of the Qosh-Tepa Canal have become a point of dispute with Uzbekistan and Turkmenistan; the Euphrates–Tigris Basin, where dam construction in Türkiye and water diversions have long affected downstream Syria and Iraq, straining regional security, food production, and intrabasin governance (10, 11); and the Nile Basin, where Ethiopia’s Grand Ethiopian Renaissance Dam (GERD) has become contentious with Egypt and Sudan (12), reflecting the complexities of upstream infrastructural expansion against downstream dependency and claims of preexisting water rights. Similarly, tensions between Kyrgyzstan and Tajikistan over transboundary water resources in the Fergana Valley and around the Golovnoy sluice on the Isfara River triggered cross-border clashes and population displacement (13). Rooted in Soviet era border demarcation gaps, tensions were intensified by changes in precipitation and glacier melt patterns in the Pamirs, resulting in reduced overall water availability and unequal access to irrigation water exacerbated by degraded shared infrastructure and weak cross-border institutions (14, 15).

Climate as a Catalyst: Climate variability and change exacerbate vulnerabilities in transboundary water resources within a complex nexus of strategic sectors. The Indus case underscores how agricultural dependency and food security are intimately tied to cross-border flows (16). Changes in monsoon patterns, intensifying droughts, declining snow and glacier cover, and more frequent extreme flows undermine river predictability and strain existing cooperative mechanisms. The Indus region, for instance, has already experienced altered monsoon variability (17, 18), whereas Central Asia has reported reduced snowpack and compounding political tensions (14, 19, 20). Such changes are threat multipliers for transboundary water tensions. Despite such tensions and threats, several transboundary basins show that cooperation is possible and beneficial (21). Examples include the Great Lakes Compact (2008), an agreement between eight US states and the province of Ontario, Canada safeguarding the Great Lakes from overextraction and pollution via shared institutional governance; and the Lesotho Highlands Water Project, an enduring partnership in southern Africa, where Lesotho’s highlands supply water and hydropower to South Africa with mutual national benefits (22).

Gaps and Opportunities: Through a series of workshops (23)^* with scientists, decision makers, and policy experts, the PEER2PEER team collaboratively develops data tools, policy options, and resilience frameworks. Common themes emerging from these meetings have revealed that effective solutions must be context specific, data-informed, and collaboratively governed. Based on our multibasin consultations and scientific analysis and in-person meetings with local partners, we offer three interlinked recommendations:

1. Beyond Water Stress: Integrating Human Dimensions

Current widely used measures of water stress [e.g., ratios of withdrawals to renewable supplies, (24)] are often used as indicators of water insecurity, stress, or vulnerability. While useful as first-order approximations, these indices can be misleading when applied to the management of transboundary waters (25). Water stress metrics typically reduce complex socio-hydrological realities to a single number often dominated by climate, ignoring the uneven social, economic, and institutional contexts in which water scarcity is experienced. In practice, the outcomes of water management decisions depend not only on hydrological conditions but also on the ability of societies to anticipate, absorb, and adapt to stress (26). This capacity is shaped by human development, financial resources, and governance quality, factors that are absent from conventional water stress indices (27).

Future progress requires a shift from purely hydrological assessments to frameworks that explicitly integrate human dimensions of vulnerability and adaptive capacity. Any meaningful analysis of water stress must combine vulnerability and coping capacity information, since hydrological scarcity alone cannot explain how societies experience or manage risk. Integrating these dimensions allows us to distinguish between regions facing similar physical shortages but with vastly different abilities to absorb impacts, adapt, and negotiate sustainable water management. For this reason, we highlight the need for a Water Resource Vulnerability and Coping Capacity (VCC) framework that can combine water stress, management capacity, exposure, governance [e.g., Human Development Index (28) and government effectiveness indices], and indicators of financial capacity/stability (Fig. 2). Such a framework moves beyond static representations of scarcity to capture the dynamic interplay of climatic variability and human systems. Countries with similar hydrological conditions often exhibit starkly different outcomes during droughts, depending on governance effectiveness, institutional capacity, and levels of economic and human development (29, 30). Fig. 2 shows examples of publicly available datasets that can be used in a VCC framework, including traditional drought information [e.g., Fig. 2A, the Standard Precipitation and Evaporation Index (SPEI); (31)], available from SPEIbase; Fig. 2B, government effectiveness [(32); one metric in the World Bank’s Worldwide Governance Indicators dataset]; and Fig. 2C, water demand per capita [(33); sourced from FAO AQUASTAT)].

Fig. 2.

Maps of (A) drought based on Standardized Precipitation Evapotranspiration Index (SPEI), (B) government effectiveness, and (C) water demand per capita in 2022. Major droughts across South America, Europe, and Central Asia affected countries with variable water demand and governance, the impacts of which are not captured by climatological drought metrics (such as SPEI) alone. As societies develop over time, integrating human impacts (e.g., water demand, governance) in water resource assessment becomes more important.

Expanding upon this logic, future assessments of transboundary water systems should incorporate a broader suite of human indicators. First, governance quality (i.e., transparency, rule of law, compliance, and institutional effectiveness) shapes how disputes are negotiated and how adaptation policies are implemented (e.g., Fig. 2B). Second, local water use/demand (e.g., Fig. 2C) determines the degree of pressure exerted on the shared resource and the dynamics of competition. Third, financial and economic capacity influences whether countries can invest in resilient infrastructure or provide safety nets to vulnerable populations. Fourth, human development indicators, such as education and health, affect how societies respond to crises and build adaptive strategies. By integrating these dimensions, vulnerability assessments will provide more realistic insights into where tensions over shared waters may emerge and where cooperation is most feasible.

Advancing the field requires decisive tools beyond water stress as a narrow metric. By embedding hydrological assessments within the broader fabric of social, economic, and institutional capacity, researchers can provide tools that better describe the causes of scarcity and ultimately help resolve the tensions that arise in managing shared water resources.

2. Closing the Data Gap

In every interaction with stakeholders, the lack of reliable, publicly accessible data emerged as one of the most pressing challenges for effective water management. The data challenges are particularly acute across international borders where “white map syndrome” is prevalent due to restrictive data coverage and cross-political boundary availability. Among these, limited runoff information was consistently identified as the most critical gap. This shortfall severely constrains our ability to anticipate, model, and manage water-related risks in transboundary basins. In regions such as Central Asia, where snow and glacial runoff provide the foundation of river flows, the absence of systematic observations is particularly acute. Ground-based monitoring networks are sparse and often discontinuous, leaving large uncertainties in seasonal water availability. This challenge was repeatedly emphasized during discussions at the annual PEER2PEER meetings, where regional scientists and decision makers highlighted the need for tailored data products to fill these blind spots. Stakeholders stressed that without reliable information on snow cover, snow-water equivalent, and melt dynamics, it is difficult to assess vulnerabilities or negotiate cooperative transboundary management strategies.

Closing this gap requires a stronger integration of remote sensing capabilities with regional knowledge. Satellite observations have already transformed our ability to monitor water resources across inaccessible terrain (34). Looking forward, there is a need for high-resolution, basin-specific products that directly support coupled water–human system models. These models must be designed not only to capture historical dynamics but also to enable scenario analysis of future extremes, such as accelerated glacier retreat or shifts in snowmelt timing (35). The development of such tools must be coproduced with regional partners. Engagement with local scientists and institutions ensures that products are relevant, interpretable, and directly usable in policy and management contexts. For example, NASA’s Surface Water and Ocean Topography (SWOT) satellite now provides unprecedented measurements of water surface elevation in reservoirs, lakes, and major rivers worldwide (36). These observations offer a powerful new lens for tracking changing water conditions, improving runoff estimation, and validating basin-scale models. When combined with snow and glacial data products, SWOT’s capabilities create opportunities to develop integrated monitoring frameworks that can inform drought preparedness, flood risk management, and long-term adaptation planning.

Closing the data gap is not solely about collecting more information; it is also necessary to make the right information accessible, usable, and actionable. By coupling advances in remote sensing with collaborative model development and local expertise, the scientific community can provide the evidence base needed to support sustainable management of shared water resources. We advocate for creation of transboundary, open-access data-sharing platforms, managed jointly by riparian governments, independent researchers, UN and intergovernmental agencies, and international stakeholders. These platforms would integrate hydrometeorological data (streamflows, precipitation, snowpack); socioeconomic indicators (agricultural demands, population and economic trends); and governance metrics (decision-making structures, cooperative agreements). Such a shared platform can support transparency, early warning, and coordinated planning, moving beyond crisis-response to proactive resilience building.

Progress in this area also depends on sustained investments in local capacity building. To address this need, the PEER2PEER team has organized a wide range of local training on remote sensing and geospatial information systems in countries such as Tanzania, Uzbekistan, and Kyrgyzstan. In parallel, the National Academies has supported several mobility fellowships for early-career scholars from Africa, Central Asia, and the Middle East to collaborate with US partners. These initiatives aim to strengthen local expertise in data analysis and processing, activities that require long-term investments to achieve meaningful and lasting impact.

3. Building Governance Regimes Trusted by Parties

Effective transboundary agreements acknowledge the importance of trust, confidence, and equity (37). All parties must feel secure in their share of available water, and regional allocation agreements should respect national sovereignty and be equitable in how they allocate intrabasin availability. In the case of Singapore and Malaysia, water-sharing agreements that transfer riparian flows from the latter to the former work because Malaysia is equitably compensated for its sharing of water while Singapore’s growing reliance on water supply innovations such as rainwater harvesting, desalination, and effluent reuse has helped reduce tensions. Both nations have agreed not to implement unilateral changes without consulting the other party (38).

For governance regimes to be effective, parties must have confidence that any agreement to share and comanage water will be honored equally by all others within the basin. This commitment requires that goals and desired outcomes are explicit in treaties and other agreements, parties are assured that violations will be caught before credibility of agreements is undermined (e.g., verification), and agreements provide tangible benefits to all parties. Moreover, parties must adhere to five principles: transparent data sharing (39), reliable monitoring (40), inclusive representation (41), reliance on third party monitors when needed (42), and cogovernance by all parties (43). A good endeavor to adopt these principles is the Nile Basin Initiative (NBI) of 1999, which strives to implement a Shared Vision among its ten member states: “to achieve sustainable socioeconomic development through the equitable utilization of, and benefit from common Nile Basin water resources.” The Agreement explicitly states that the underlying principles of cooperative action in the Nile Basin are “benefit sharing and confidence building,” with stakeholder engagement essential to both (44–47).

Transboundary water challenges are found throughout the world. South American experiences reinforce the importance of mutually beneficial agreements and solutions acceptable to affected parties. The 1978 Amazon Cooperative Treaty signed by Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, and Venezuela, and its ancillary agreements encompassing specific projects addresses intrabasin land use, species protection, indigenous justice, public health, and integrated water management through shared monitoring and evaluation protocols and conjoint financing by member states. Elsewhere, conflict between Chile and Bolivia over utilization of the Silala basin has led both countries to seek amicable redress through the International Court of Justice. While the parties agree that the customary obligation to prevent transboundary harm applies to the entire basin, as the Court ruled in 2022, they continue to disagree over the threshold defining “significant harm” (48–50).

Two other examples, in principle, are the Mekong and Indus River basins. In the former, a 1995 agreement commits basin states to “reasonable and equitable use” and cooperation in ensuring sustainability of the basin’s water for hydropower, water supply, irrigation, navigation, and flood control (51). Similarly, the 1960 Indus Waters Treaty has sought equitable allocation of the basin’s tributaries among parties geographically—assigning western streams to Pakistan and eastern rivers to India. A Permanent Indus Commission requires prior notification of river development plans (52). In all three cases, however, adherence to these principles of confidence building have been challenged by competing national development pressures, political distrust, and failures to confer with one another when launching new water infrastructure. This has sometimes led to diplomatic impasse (Indus Basin), failure to address the needs of marginalized groups [Mekong basin, (53)], and disagreement over water withdrawal, storage, and diversion rights [e.g., Nile Basin, (46)], particularly between upstream and downstream states (i.e., Ethiopia, Egypt).

In an effort to build trust and evidence-based governance, PEER2PEER designed a training on “Confidence building in resolving transboundary water disputes” in partnership with the United Nations University Institute for Water, Environment and Health (UNU-INWEH), known as the UN’s Think Tank on Water. The first training was delivered in Dodoma (Tanzania) on June 23, 2025, to representatives from the Ministry of Water of the Republic of Tanzania. It covered discussions of conflict databases and their use as investigative/analytical tools for understanding confidence building, as well as major principles entailed in building confidence including structuring equitable agreements, transparent monitoring, and data-sharing protocols. It also featured role playing exercises on how to formulate durable, verifiable agreements to diffuse conflict and create a sustainable transboundary management regime. The curriculum for this training can be applied to other participating networks and regions. Capacity building activities and cross-border knowledge sharing can be used as strong confidence building activities to bring Parties together, create transparency in the negotiation process, and provide a shared understanding of expectations.

From Flashpoints to Lifelines: The 2025 India-Pakistan crisis, a moment when water threatened to become a tool of war, is a clear warning. Yet, it also illuminates the stakes and the necessity of science informed collaboration. Across different basins, we have seen how trust, shared data, and inclusive governance can transform shared watercourses into bridges, not battlegrounds (54). If we commit to weaving together science, diplomacy, and local voices, and build codesigned data platforms that reflect both hydrology and humanity, we can reshape the future of transboundary waters as foundations of regional stability, ecological integrity, and societal well-being.