Rivers, lakes and aquifers do not stop at borders. They move as gravity dictates – binding upstream and downstream states into relationships they cannot ignore.
A dam, diversion project or pollution event in one country can quickly become water scarcity, flood risk or ecological damage in another. Shared water is therefore never purely domestic. It sits at the intersection of development, diplomacy and climate resilience. This becomes crucial as transboundary basins account for around 60 percent of global freshwater flows and are vital to roughly 40 percent of the world’s population [1].
Why shared water demands shared rules
Over time, states have moved from ad hoc bargaining to more formal legal norms and basin institutions. Two milestones were the 1992 Water Convention and the 1997 UN Watercourses Convention. Together, they established principles that still shape water diplomacy: equitable and reasonable use, the obligation to avoid significant harm, data sharing and institutionalised cooperation [2,3]. Their significance lies in how they shift the debate from “who owns the water?” to “how should shared water be governed fairly and sustainably?”
In practice, cooperation varies. The International Commission for the Protection of the Rhine is cited as a strong model for managing water quality, flood risk and ecosystem recovery [4]. In West Africa, the Organisation for the Development of the Senegal River treats the basin as a shared development space [5]. The Mekong River Commission, meanwhile, provides a platform for coordination and data-sharing in a politically sensitive region [6].
Climate change is stress-testing old agreements
As climate risks intensify, the basic need for fairness and cooperation has not changed, but pressure on shared waters has intensified. Hotter temperatures, erratic rainfall, droughts, more intense floods and glacier loss are making river flows harder to predict. Many agreements were built around historical averages, and those are becoming less reliable [7].
This challenge is particularly pronounced in climate-vulnerable river basins across Africa and Southeast Asia, where water insecurity often overlaps with food insecurity, energy demand and limited adaptive capacity. In the Nile Basin, climate stress is heightening tensions over development and downstream water security, including around the Grand Ethiopian Renaissance Dam – a large hydropower project that has sharpened disputes between Ethiopia, Sudan and Egypt over water flows and filling schedules [8]. In the Mekong, projected shifts in rainfall and runoff raise concerns for fisheries, agriculture and flood management [9]. In each case, it is often the most marginalised communities, such as smallholder farmers, women, and young people who bear the consequences of governance failures [10].
Therefore, the impact of climate change is best understood as a threat multiplier. It deepens scarcity, increases uncertainty and exposes weak institutions. Where trust is low and rules are vague, climate shocks can sharpen tensions. Where institutions are stronger, the same shocks can create incentives for deeper cooperation. The Rhine’s “Rhine 2040” programme shows how older institutions can adapt to new climate risks rather than collapse under them [11]. Through the programme, countries in the basin have agreed to plan jointly for floods, droughts, low water levels and ecosystem protection, showing how long-standing river institutions can update their work as climate risks evolve [12].
From water-sharing to risk-sharing
In a warming world, the policy challenge is no longer just how to divide water, but how governance can respond to developmental challenges that are aligned with ecological integrity.
One useful lens is Integrated Water Resources Management (IWRM). Rooted in the 1992 Dublin Principles, it treats freshwater as finite and vulnerable, emphasises participatory governance, recognises the central role of women, and acknowledges water’s social and economic value [12]. Used as intended, it shifts the focus from allocation to coordination, equity, sustainability, and basin-wide resilience.
In concrete terms, this means moving towards real-time data sharing, joint flood and drought forecasting, and climate-informed basin planning with rules that can adapt as hydrological conditions change. It also broadens the agenda beyond water volumes to interconnected outcomes such as food security, energy systems, navigation, ecosystem protection, and disaster risk reduction.
At its core, transboundary water governance has shifted from dividing scarce water to managing shared risk, building resilience across borders, and ensuring that those most exposed, including future generations, have a voice in how that is done.
