Assessing water security through hydrologic modelling in Olifants River basin, South Africa.

The Olifants River watershed is one of the largest river basins of South Africa and the activities in this watershed contribute approximately six percent to the total Gross Domestic Product (GDP). The Olifants River flows through the Kruger National Park (KNP) before reaching the Indian Ocean. Given the sensitivity of the species in the KNP there is a strong need to understand the lowflow conditions in the segment of the river that flows through the park. Water availability and water management problems have been reported during the various drought periods in the recent past and water security is threatened due to climate change. The objectives of the present study are to evaluate the water budget of the Olifants River watershed and to assess the impacts of climate change on the hydrologic regime. Soil and Water Assessment Tool (SWAT) was implemented to simulate the hydrologic regime of the watershed. The model was calibrated and validated for the period of 1997 to 2003 and 2004 to 2010, respectively. To assess the impact of climate change on water security, the calibrated model is forced with future climate data for the years 2041 to 2070, extracted from Coordinated Regional Climate Downscaling Experiment (CORDEX). The model is being used to evaluate different water management scenarios to ensure environmental flow requirements. A shift in the precipitation pattern and an increase in the temperature is found when compared to the base period climate data from 1976 to 2005. Consequently, significant changes are also found in the average monthly streamflow patterns of the river. The results are being used in developing a long- term water management strategy for the watershed with a focus on meeting the low flow requirements in the stream.