|The UN Watercourses Convention codifies numerous principles of customary international law related to the nonnavigational use of international watercourses and these principles served as the conceptual framework for the Convention. For instance, a fundamental principle included in the Convention is that of Equitable and Reasonable Utilisation, which is explored in Part II.
At this stage it is important to mention that the Convention actually goes beyond simply codifying customary law, and also clarifies the content and scope of specific rules and principles, providing minimum standards for interpretation. For example although countries may accept the customary legal status of the principle of equitable and reasonable utilisation and the no-harm rule, this does not mean that all states share the same interpretation of these norms including their scope, meaning, how they relate to each other, and, ultimately, how they should be implemented in a harmonious manner. The Convention’s role in this instance is to provide common ground for interpretation, arrived at after discussions amongst relevant parties. The existence of a minimum standard to be followed by all countries would make them a priori aware of their general rights and obligations. A clearer status of the applicable law through codification is crucial to prevent disputes and thus promotes stability and consistency among riparians.
Furthermore, the role of the ILC in drafting the Convention was not only the codification of existing customary international law, but also its progressive development and the crystallisation of emerging norms (e.g. ecosystem protection). In addition, the Convention incorporates the rights and obligations which support substantive rules and principles – i.e. procedural rules covering issues like the exchange of data and information, consultations and negotiations, and dispute settlement. Finally, since states have to implement its provisions in their entirety, the Convention serves as an overarching umbrella addressing the multitude of issues arising out of present and future conflicts over water, and preventing the parties from following a ‘selective’ approach regarding the management of international watercourses – that is selectively picking which customary principles they choose to follow.
Furthermore, the ambiguities and abstractness of customary law make it harder for the international community or affected individuals to question joint governmental decisions. This becomes relevant where all co-riparians agree on the implementation of a certain project by one state based on tradeoffs regarding future river development elsewhere or on the sharing of benefits deriving from such a project. In such a case, the Convention, more than custom, would inform an analysis of whether the decision conforms to minimum duties related to environmental protection and human rights.173
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Relationship with UNECE Water Convention