This research set out to develop a deeper theoretical component to the emerging discipline of hydropolitics by studying the political aspects of institutional developments in the water sector. The focal point was the four international river basins that are shared between South Africa and six of its neighbouring states. The study found that while there is a lot of evidence for the securitization of water resource management in South Africa's international river basins, there are also a number of examples of regimes. The creation of these regimes was driven primarily by threat perceptions relating to state security, mostly during the period of apartheid and the Cold War. These regimes were mostly robust and served as a valuable instrument for the de-escalation of conflict, which was primarily of a high politics nature. Examples of both plus-sum and zero-sum outcomes have been isolated. Plus-sum outcomes arose when the non-hegemonic state chose to view the offer of a regime in terms of national self-interest with four examples of this condition. In all four cases the non-hegemonic state benefited from cooperation with South Africa. Zero-sum outcomes arose when the non-hegemonic state chose to view the offer of a regime in terms of ideology with two examples of this condition. In both cases the non-hegemonic state did not benefit and was sidelined to the extent that they became marginalized and worse off than before. In all cases the hegemonic state benefited from the regime. The research consequently showed that a hydropolitical complex is emerging in Southern Africa, clustered around two international river basins, the Orange and Limpopo, which have been defined as pivotal basins. Both of these basins have reached the limit of their readily available water resources and future development is not possible on any great scale. Four of the most economically developed states in Southern Africa (Namibia, Botswana, Zimbabwe and South Africa) are riparians on these two international river basins, and have been defined as pivotal states. Other less developed countries that share any international river basin with a pivotal state have been defined as an impacted state, because their own development aspirations have been capped through this association. Any international river basin that has at least one of the pivotal states in it has been defined an impacted basin. Finally, this research showed that regimes create a plus-sum outcome in closed international river basins because they reduce the levels of uncertainty and institutionalize the conflict potential. As such regimes are a useful instrument with which to regulate inter-state behavior, leading over time to the development of institutions consisting of rules and procedures.