Boundaries of benefit sharing: interpretation and application of substantive rules in the Lake Malawi/Niassa/Nyasa sub-basin of the Zambezi Watercourse

The primacy of state sovereignty in transboundary water resources management raises questions regarding how riparian states determine “who gets what, where, and why” in a shared watercourse. To facilitate peaceful coexistence, substantive rules—“equitable and reasonable utilisation (ERU)” and “the duty to prevent the causing of significant harm”—define rights and responsibilities of riparian states in the utilisation of shared watercourses. The duty of riparian states to cooperate, as a principle of international law, plays an important part in realising these substantive rules. This article critically reflects on the principles underlying transboundary water management by focusing on the interpretation and application of substantive rules in the Lake Malawi/Niassa/Nyasa sub-basin of the Zambezi River Basin in Southern Africa. The case study demonstrates how interpretation and application of international water law are generally in line with customary practices, but are subject to highly localised decision contexts which challenge Southern African Development Community (SADC) attempts to establish a firm legal foundation upon which to guide access, use and management across the region’s shared river basins.