Assessment of the Impact of Climate Change on Meka Stream Flow, Oromiya, Ethiopia

Abstract

Due to climate change producing shifts in hydrologic cycles developing countries, such as Ethiopia and/or sub-Saharan countries, are among those most threatened by water stress, in view of the likelihood of extreme variability, seasonality, and decreasing stream-flows that are predicted to occur in the coming decades. The general objective of this study is to assess the impact of climate change on Meka stream flow due to Meka stream flow is on decrement from time to time. Therefore it is important to assess climate change to plan how to adapt to climate change, and how to mitigate the changes. For this study meteorological, hydrological and spatial data are used as input to SWAT hydrological models. The climate model variables (precipitation and temperature) were obtained from Coordinated Regional Downscaling Experiment (CORDEX) under representative concentration pathway (RCP4.5) and (RCP8.5) scenarios for CCLM4-8-17, RACMO22T and RCA4. Before temporal variation was estimated, the projected precipitation was bias corrected using power transformation and temperature was bias corrected using Variance scaling. Projected rainfalls, temperatures and stream flows were estimated for two consecutive p eriods of 2021-2051 and 2051-2080 for both scenarios. The performance of SWAT model for observed data and simulated baseline climate models data were evaluated using coefficient of determination (

), Nash Sutcliffe Efficiency (NSE) and percent bias (PBIAS) using observed stream flow data of the year 1988-2000 and 2001-2005 for calibration and validation respectively. The Assessment of climate change impact on the stream flow was made on monthly, seasonally and annual based for selected three models. The monthly average percentage of change of discharge were (-30.33%, -29.75%), (-27.49%, -26.58%) and (-28.41%, -28.36%) for short term and (-29.63%, -30.1%), (-25.02%, -25.16%) and (-25.87%, -26.37%) for long term for CCLM4-8-17, RACMO22T and RCA4 under RCP4.5 and RCP8.5 respectively. The seasonal and annual based climate change impact assessment indicates that the discharge will be expected to be decreased. The RACMO22T was selected as better discharge simulating regional climates model based on simulated discharge under RCP4.5 and RCP8.5. Expected discharge will be decreased for all months of the year, which also decrease seasonally. Percentage of variation was small for long term than short term which indicates the stream will not face drought in future.