This paper seeks to complement ongoing discussions around water allocation by offering an analytic framework for examining the evolution of paradigms for water allocation in river basins. It traces this evolution from the hydraulic paradigm through to Integrated Water Resources Management (IWRM) and the current water security paradigm. Using a society-science-practice interaction perspective, the paper draws attention to the governance processes of water allocation that underlie these paradigms using examples from river basins in southern Africa. It is argued that the process of allocating water resources is often influenced by societal priorities and values that do not necessarily result in maintaining ecosystem health and integrity. The efficacy of water allocation depends on the extent to which implementation takes into account the socio-political dynamics associated with collective action involving multiple water users. While paradigm shifts provide windows of opportunity for strengthening legislation, the mere adoption of paradigms should not be taken as a panacea for addressing challenges associated with water allocation in river basins. This is especially relevant for several countries in southern Africa that are undertaking water reforms with the view of strengthening allocation of water resources at basin scale.