Impact of climate change on surface water potential in Borkena watershed

Abstract

Nowadays, the world climate change is acquiring series issue against surface water potential. Climate change affects stream flow timing through the temperature increase and change for precipitation. Changes in the duration of rainy season can affect river flow. Therefore, this study, evaluate the impacts of climate change on surface water potential of Borkena River, under the newly representative concentration pathway scenarios RCP4.5 and RCP8.5. The study used highresolution dynamical downscaled climate data and new climate scenarios. Dynamically downscaled daily rainfall and temperature data were obtained from international water management institute, and all meteorological data (maximum and minimum temperature, precipitation, humidity wind speed and sunshine hour) were collected from national meteorology agency. The downscaled future climate data have undergone bias correction before any analysis. Then Current evaporation data estimated by FAO recommended Penman – Monteith method while future evapotranspiration was estimated by Hargreaves method. Hydrological engineering center of hydrological modeling system model used to examine the effect of climate change on stream flow. The hydrological model calibrated from 2003 – 2010 and validated from 2011 -2015. The performance of the model assessed by Nash – Scatilffe (NSE= 0.714 & 0.615), coefficient of determination (R2 = 0.777 & 0.652) and relative volume error (RVE = 4.0% & -13%) during calibration and validation process respectively. According to Mann–Kendall trend test the projected climate variable (temperature, annual rainfall and evapotranspiration) showed on increasing trend. The projected average maximum temperature will be increasing by 1.1690c and 1.5120c for RCP4.5 and RCP8.5 in the middle term period (2041 – 2070) relative to base line period respectively. In addition, the precipitation indicates that increase by 7.119% and 7.99%mm in the future period (2041-2070) under RCP4.5 and RCP8.5 respectively. Average annual stream flow volume will increase up to 13.13 % and 15.44% under RCP4.5 and RCP8.5 scenarios for the middle term period respectively. The impact of climate change analysis was control on surface water potential (runoff volume) in hydrological model.