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 were 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
the minimum temperatures increase for the two scenarios in all future time horizons. The
mean annual rainfall data from the power transformation analysis revealed upward pattern in
some years and downward pattern in others. 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 the 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.
