Abstract

Climate change significantly affects many hydrological systems, which in turn affects the runoff and the flow of rivers in Gidabo river basin. Therefore, the aim of this research was taken as to investigate the impacts of possible future climate change scenarios on the runoff in the catchment area of Gidabo River. Statistical Downscaling Model version 4.2 was used to downscale the daily precipitation, daily maximum and minimum temperature in the basin of the study area. The large-scale climate variables for the A2a and B2a scenarios obtained from the Hadley Centre Coupled Model version 3 were used to show future scenario. After the calibration of the model and testing of the downscaling procedure, the hydrological model was run for the three future periods: 2011-2040, 2041-2070, and 2071-2099. The meteorological variables such as, precipitation, minimum and maximum temperature that were downscaled from SDSM were used as input to the SWAT hydrological model which was calibrated (R=0.77) and validated (R=0.81) with meteorological and hydrological historical data (1980-2006) to examine the possible impact of climate change on the runoff of the catchment. The results obtained from this study indicate that there is significant variation in the monthly, seasonal and annual runoff. The SWAT simulation of future average seasonal runoff shows increasing pattern during February to May and June to September for both A2a and B2a scenarios in all time periods. The change in climate variables such as increase in precipitation and temperature thereby which is very sensitive parameter that can be affected by changing climate than any other hydrological component are likely to have significant impact on runoff.

Keywords: Climate change; Gidabo river basin; Statistical Downscaling Model (SDSM); Stream flow