Managing water under climate change for peace and prosperity in Swaziland

Abstract

The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1.0–3.5 °C) and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation (±20%). The impact of expected climate change will affect almost all aspects of human endeavour. The major focus of this paper is management of water resources under climate change for peace and prosperity in Swaziland. The impact of climate change on hydrology and water resources has been evaluated using general circulation model (GCM) results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rainfall runoff model. The evaluation of the effect of climate change on hydrology and water resources in Swaziland has been carried out in three catchments namely: Mbuluzi, Komati and Ngwavuma. MAGICC model was used to simulate the climate parameters for Swaziland given the baseline conditions. Eleven GCMs were evaluated and three of them were found to simulate very well the observed precipitation for Swaziland. These GCMs are: the Geophysical Fluid Dynamics Laboratory (GFDL), the United Kingdom Transient Resalient (UKTR) and the Canadian Climate Change Equilibrium (CCC-EQ). The three GCMs were used to project the temperature and precipitation changes for Swaziland for year 2075. This information was used to generate the temperature, precipitation and potential evapotranspiration values for the three catchments for year 2075. This information was used as input data to a calibrated WatBall rainfall runoff model. Simulation results (after taking into consideration water use projections) show a water deficit from June to September in both the Komati and Ngwavuma catchments and a water deficit from May to September in the Mbuluzi catchment. Efficient water utilization in the agricultural sector (i.e., using drip irrigation) gives a water savings of 33.6 × 10 6 m 3per year (1.065 m 3/s), 47.6 × 10 6 m 3per year (1.509 m 3/s) and 16.8 × 10 6 m 3 per year (0.533 m 3/s) in the Komati, Mbuluzi and Ngwavuma catchments, respectively. The saved water could be used for other economic activities and meeting Swaziland’s water release obligations to downstream riparian states of South Africa and Mozambique.