Jonathan I. Matondo, University of Swaziland, Geography, Environmental Science and Planning, matondo@uniswa.sz
The southern African region has been projected to receive less precipitation and Swaziland is no exception. The average results (precipitation, potential evapotranspiration) of 12 general circulation models (GCMs) in the future (2021 to 2060) and the observed stream flows were input to a calibrated rainfall runoff model (Watbal model) in order to determine the water resources in four catchments in Swaziland under expected climate change. Simulation results show that, the present streamflow lie within the 95% confidence interval of the projected flows in all the catchments. This implies that there is no significance difference between the observed and projected stream flow at 5% confidence level. However, the runoff change between the 2.5% and 97.5% quantile ranges from -17.4 to 26.6; -31.2 to 18.1; -40.3 to 27.7; and -40.8 to 34.9% in the Komati, Mbuluzi, Usutu and Ngwavuma catchments respectively and the median of the runoff change is negative for most of the months in three catchments (Usutu, Mbuluzi and Ngwavuma) except for the Komati catchment. Thus, there will be less runoff in the three catchments under expected climate change. Therefore, there will be less runoff in the three catchments and adaptation options for Swaziland are proposed.
Keywords: Climate change, streamflow simulation, runoff change, statistical significance, adaptation options