EVALUATION OF HYDROLOGIAL IMPACTS OF CLIMATE CHANGE ON THE BORKENA CATCHMENT NORTH EASTERN, ETHIOPIA

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.