The role of reasonableness in assessing equitable and reasonable use

The objective of this paper is to examine the relationship between "equitable" and "reasonable" in the law of international watercourses. The analysis will be informed by two of the key distillations of international water law: the provisions of the United Nations Convention on the non-navigational uses of international watercourses, and associated commentary; the Helsinki Rules on the Uses of the Water of International Rivers. The analysis will also reflect on relevant experience from the U.S.A. through its application of equitable apportionment in inter-state conflicts, through eastern state practice in implementing riparian rights regimes, and through the western concept of beneficial use. The paper seeks to identify the role of reasonableness in assessing the extent of riparian states’ rights to Transboundary watercourses. The paper concludes that equity and reasonableness have distinct and separate roles to play, but that they cannot be analysed in isolation of the concept of beneficial uses.