Summary

International water law plays a key role in guiding states’ behavior over water resources they share. Substantive and procedural principles provide an ex ante framework based on which states can interact in a manner that prevents or mitigates potential conflicts and fosters cooperation and its benefits while supporting the sustainable use and management of these transboundary resources. Through the international water law regime, cooperation has largely prevailed over conflict in the world’s transboundary basins. Nonetheless, international water law—and thus also its role in conflict prevention and cooperation promotion—faces various challenges as populations and economies grow, the climate changes, and states seem to increasingly value short-term unilateral considerations over long-term multilateralism gains. This will challenge key principles, such as the principle of equitable and reasonable utilization and the principle of no significant harm, and their implementation in different basins, possibly triggering new disagreements between riparian states. It will therefore be important for international water law to remain adaptive to change and ensure the long-term cooperative and sustainable governance of water resources shared between states.