ABSTRACT
This chapter focuses on the conceptual origins, normative nature and legal implications of the two key substantive rules of general international water law – that is, the principle of equitable and reasonable utilisation and the duty to prevent significant transboundary harm. The principle of equitable and reasonable utilisation represents a compromise between two extreme and uncompromising positions regarding the right conferred upon states, by virtue of their territorial sovereignty, to utilise shared transboundary water resources found within or passing through their territory. Whereas equitable and reasonable utilisation provides the cardinal, overarching rule of international water law, almost all international water resources agreements and codifications include a closely related obligation on watercourse states not to cause significant harm to other watercourse states. The principle of equitable and reasonable utilisation involves the allocation of rights in the uses and benefits of shared water resources on the basis of a distributive conception of equity having regard to all relevant factors.
