Transformation of climate and its sway on hydro-climatology using representative concentration pathways (RCP) in Geba catchment of Ethiopia

Frequent change in climate and its inconsistent characteristic across Ethiopia at the behest in regional scale encourages researchers in suitable planning of the strategies for adaptive capacity. Geba catchment in this region not only put influence by the hydro-climatic conditions but also extends to assess the ongoing impacts. Regional Climate model (RCM) outputs using representative concentration pathways (RCP) including climate change scenarios of precipitation, temperature, and stream flow for three span of time firstly 1976–2005, second 2021–2050, and the last 2051–2080 has been evaluated. Non-linear power transformation for precipitation and linear shifting and scaling for temperature climate datasets was applied by extrapolating existing climate dataset. Pragmatic use of HEC-HMS, the hydrological model was pledged to generate current and future climatic condition in stream flow of Geba catchment. In an average, the respective performance of the model reveals a Nash Sutcliffe Efficiency (NSE) of 0.83 and 0.80 during calibration and validation. The trends of projected climate variables have shown positive change for temperature and potential evapotranspiration whereas stream flow showed a declining trend with manifestation in precipitation. In comparison to the base period, the average maximum temperature may rise by 1.25 °C, 2.01 °C for RCP4.5, 1.67 °C, and 3.39 °C for RCP8.5 for a period 2021–2050 and 2051–2080 respectively. For the same period, an increase in minimum temperature was recorded under RCP4.5 and RCP8.5. The annual precipitation may decrease by 2.94% and 3.32% for RCP4.5 and 2.01% and 3.1% for RCP8.5 for 2021–2050 and 2051–2080 respectively. Besides, annual evapotranspiration may increase up to 2.6% and 4.3% for RCP4.5 and 2.5% and 3.0% for RCP8.5. Overall, the mean annual stream flow indicates a decreasing order from 0.93 to 1.67% for RCP4.5 and by 1.3 to 1.76% for RCP8.5. This provides a detail analysis that climate change affects the water balance of Geba catchment.