Abstract
The Tigris-Euphrates basin is of high regional and global significance; however, the lack of a comprehensive multilateral agreement among riparian states has transformed the management of this transboundary watercourse into a political, security, and environmental challenge. The central issue addressed in this research is the evaluation of the quality of the application of the 'no significant harm' principle within the basin. Specifically, the study investigates whether water resource utilization—such as constructing dams beyond the natural capacity of the rivers and excessive extraction of groundwater—complies with legal obligations and the principles of equitable and reasonable utilization. This study employs an innovative interdisciplinary approach that integrates legal and technical analyses. The legal framework is established by examining customary sources, international conventions, and the insights of prominent international law scholars regarding the definition and scope of "no significant harm." Concurrently, up-to-date technical data on dam capacities, river flow alterations, and groundwater extraction—sourced from reputable publications—serve as the empirical basis for assessing the practical application of the principle. The findings indicate that mismanagement practices in water resource development can inflict significant harm on the ecosystem, regional wetlands, and the livelihoods of local communities. Therefore, the formulation of a comprehensive framework and the advancement of multilateral cooperation for the equitable and reasonable use of the TigrisEuphrates resources is imperative.