Management of large water resource systems

South Africa has one of the most complicated and integrated water resource systems in the world involving numerous interlinked river systems and major interbasin transfer schemes. The management of the various schemes has become a key issue over the past 15 years resulting in the development of sophisticated systems models which are now used to analyse and operate all of the country's major schemes. The models have been developed through a partnership between the Department of Water Affairs and Forestry in association with several of the country's consultants specialising in this area of expertise. The models have now reached a stage where they are considered to be both practical and sufficiently robust to use in other parts of the world. Australia and South Africa are quite similar in many respects with regards to the water resources and climate. Both countries share the same problem of large and or semi-arid areas together with areas where the local water resources are insufficient to meet the existing or predicted future demands. Environmental considerations are also of major importance in both countries which in turn necessitates the effective use of the available resources before any new resources can be developed. In order to use the available water effectively much effort has been placed on various aspects of Water Demand Management in order to reduce leakage and excessive consumer use. It is also necessary, however, to ensure that the raw water resources are managed in an efficient and practical manner something that is often easier said than done. This paper provides general details of the system analysis techniques that have been pioneered in South Africa and discusses the most recent developments that can be used to assist water resource managers in the analysis and planning of their water resource systems.