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Evaluation and Proper Management of Valuable Water Resources
Orange River Basin, South Africa


The Orange River Development Project Replanning Study (ORRS) was commissioned in the mid-1990s to determine a strategy for the most beneficial utilization and optimal development of the water resources in the Orange River.


The Evaluation of Available Water Resources project involves the real-time management of the Orange River Project to ensure the most beneficial utilization of the resource for hydro-power generation and primary water users, while maintaining selected reliability of supply to users. The project also included annual operating analyses from 1995-2002.


Project Goal

To conduct a real-time study and maintain operation at optimal levels in the Orange River Basin based on The Orange River Integrated Water Resources Management Plan.


The Orange River Integrated Water Resources Management Plan determined the status quo in the Orange River basin in terms of available information and areas where gaps in information need to be addressed.


Project Scope

The project included:


  • Conducting the full hydrological study: The Orange River System Analysis (ORSA)
  • Real-time management of hydro-power resources
  • Determine status quo for Orange River supply capabilities


  • Produced a hydraulic model for the Orange River (ISIS) which was modified to simulate spatially and temporally varying evaporation losses and to include a variable time step facility.
  • Development options were identified for realizing the remaining potential of about 1 735 million m3/a from the Orange River.
  • Key deliverables for the annual operating analysis includes the release schedules from Gariep and Vanderkloof dams, optimize hydropower generation, imposing water restrictions, extending the system to include other important water supply systems and development of operating rules.