Development, testing and installation of a real-time ecological Reserve implementation method for the Thukela River

Sponsor: Water Research Commission
Leader: Prof DA Hughes
Staff: Ms D Louw (Water for Africa), Mr SJL Mallory (Water for Africa)
Duration: April 2005 - May 2007

The aims of this project were to develop and test a computer based real time Reserve implementation method and to apply the method to the Thukela River with the cooperation of the KZN Regional Office of DWAF. The focus of the project has been on the practical implementation of the ecological Reserve with the main emphasis on the low flow component. The basic principle is to make use of near real-time rainfall data and a pre-calibrated rainfall-runoff model to generate the natural flow signal required to specify a Reserve requirement at any point in time and at various sites within the total basin. The developed model integrates the Reserve component with the operating rules required for reservoirs and water users to ensure sustainable and equitable water management.

The final report for this project was submitted to the Water Research Commission during September 2007, having been discussed at the final WRC reference group meeting. The conclusions of the report were that the method that has been developed can be applied and is suitable for integrating the ecological Reserve requirements in a comprehensive approach to real-time water management. There are, however, a number of limitations to the successful implementation of the method.

The first limitation is related to the availability of the rainfall data required to generate the natural flow signal. The project has highlighted the severe reduction in available rainfall data that has occurred within South Africa over the last decade. The second limitation is related to the management capacity of regional water resource organisations. The implementation method relies very heavily on the use of water restriction (or supply curtailment) rules during dry periods when there is not enough water available to satisfy all requirements. It is apparent that many water managers do not have the capacity, or the legislative control, to limit water supplies and therefore the water resources cannot be effectively managed.

The third limitation is related to the management of the short duration high flow releases from reservoirs that are required to satisfy one component of the ecological Reserve. While the low flow component of the method has been demonstrated to be effective with the type of rainfall information that can be typically collected in real-time, this is not true for the high flow component. The main problem lies in the fact that decisions about high flow releases have to be made much faster (than for low flows) if they are to be efficient and effective. This means that water managers need a realistic forecasting tool that can provide them with the basis upon which to make a release decision. The project concluded that either adequate forecasting tools, or the data to support such tools, are not yet generally available in South Africa. This is a limitation that may disappear in the near future as progress is made in the application of regional climate models and the generation of forecast simulated spatial rainfall fields.  

Apart from the final report, the project results are being published in a peer reviewed journal article that is nearing completion of the review process, as well as being presented at an international conference.

This project has links with a DWAF consultancy project being managed by Water for Africa to make recommendations about the best methods of 'Operationalising the Reserve'. The method that has been developed for the Thukela basin is being established and tested in several other basins throughout South Africa and a wide range of DWAF staff are involved in assessing the applicability of the approach. As part of this DWAF project, new methods of establishing economically and socially equitable curtailment rules for all water sectors are being investigated. The basis for this assessment is a combination of the impact of curtailment rules on individual water use sectors as well as the combined impact, across all sectors, within a specific water resource management area (a river basin).

Last Modified: Fri, 14 Aug 2015 10:42:42 SAST