Abstract:
The present study investigates the hydrological impacts of climate change in essence,
changes in precipitation and temperature over the Borkena catchment based on a sample of
Coupled Model Inter comparison Project version 5 (CMIP5) downscaled over the Africa
Coordinated Regional climate Downscaling Experiment (CORDEX) domain by a Rossby
Centre regional atmospheric model version 4 (RCA4) output, under RCP 2.6 and RCP 8.5
scenarios. Linear and power transformation bias correction methods was used to improve the
simulation output of RCA4 regional climate model with high correlation to the observed
data. The bias corrected data were then used as input to the HBV model to simulate the
corresponding future runoff regime in Borkena catchment. The future projections are made
for two time periods; 2021-2040 and 2081-2100.The result revealed that the maximum and
minimum temperatures increase for all the two scenarios in all future time horizons.
However, precipitation does not show a systematic increase or decrease in all future time
horizons. The model output shows that there may be an annual decrease in runoff depth up to
29.5% for both scenarios in two benchmark periods in the future. There may be a significant
increase in runoff during the Belg season (indications of up to 12.1%) and decrease in runoff
during the Kiremit season (indications of up to 36.1%) and Bega season (indications of up to
36.6%). Based on the results of present analysis, the increase in Belg season runoff would
have paramount importance for small scale irrigation activities practiced by local farmers.
Results from incremental scenario indicate that the impact of climatic variability in Borkena
catchment is higher in precipitation than temperature change. A significant conclusion from
the study is that changes in rainfall have larger effects on runoff.
