ABSTRACT The management of international watercourses requires both scientific input and transnational cooperation. This paper examines the role of science in the field of international water law and how scientific data, techniques, and methods may be used to bestow the legal framework with greater clarity and precision. In this regard, this paper demonstrates how the two primary obligations of international water law – the no-harm principle and the doctrine of equitable and reasonable utilization – are capable of conceptualization and application in a scientific manner. Examples of interdisciplinary approaches and expert commissions are utilized to demonstrate the role of science in practice.