Customary Principles of International Water Law

Abstract

The evolution of customary principles in international water law is ongoing. This chapter presents the current status of customary principles and discusses how these principles are correlated. The relationship between the core substantive principles, equitable and reasonable utilization and the no-harm rule, has been a highly controversial issue in international water law, particularly among Nile riparian states; however, current court and state practice arguably support the primacy of equitable and reasonable use. Both principles are generally recognized, although their detailed normative content, and thus their application, remain difficult to determine precisely. Furthermore, obligations exist to protect international watercourses and their ecosystems, but international water law is still developing with regard to environmental protection in watercourse management and use allocation. Given the general character of these substantive principles, the procedural obligations of cooperation, notification, consultation, and the exchange of data and information are particularly important. The obligation of prior notification includes the obligation to undertake an environmental impact assessment if a planned measure may have a significant adverse impact on shared water resources. These procedural principles ensure that the substantive rights and obligations of the riparian states translate into effective cooperation.