Evaluation of the impact of climate change on hydrology and water resources in Swaziland: Part II

Abstract

The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1–3.5 °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 the sectors of the human endeavor. However, the major purpose of this paper is to evaluate the impact of climate change on hydrology and water resources for Swaziland. The impact of climate change on hydrology and water resources has been evaluated using General Circulation Model 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. The missing rainfall data in the original raw data files was estimated using regression analysis from the long-term daily averages rearranged in columns. Pairs of stations were analyzed to establish the ones that correlate the best in terms of the r 2. Based on the relationship established in each pair, the linear formulae were applied on the larger original data files to estimate and fill the missing data gaps. The gaps in stream flow series were filled in using rainfall-runoff modeling technique. MAGICC-model has been used to simulate the climate parameters for Swaziland given the baseline conditions. Eleven GCMs were used 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 show that there will be an annual runoff change of ±5% in the Komati catchment and ±2% in the Mbuluzi catchment given climate change conditions. Simulation results show a negative annual runoff change ranging from 4% to 23% in the Ngwavuma catchment under climate change scenarios.