Evaluation Of Climate And Land Use Land Cover Change Impacts On Stream Flow Of Guder Catchment, In The Upper Blue Nile Basin In Ethiopia

Abstract

Changes in watershed hydrology are mainly driven by changes in land use and climate. This study Evaluate Climate and LULC change impacts on Streamflow in the Guder catchment in Upper Blue Nile Basin. Specifically, dynamical downscaled rainfall simulations were evaluated for selected three RCMs output and one ensemble was undertaken byRCA4. A suite of performance measures such as Bias, RMSE, correlation coefficient and coefficient of variability of basin averaged annual rainfall amount was used to assess performance of climate models output from CORDEX Africa. Calibration and Validation of the study area was done by using SWAT CUP SUFI 2 and three main performance measurement criteria such as R2, NSE and Bias. Short term and RCP 4.5 scenarios was used to evaluate stream flow on CC and LULC. The performance Evaluation of the GCMs model shows that, CCNMR model performed -0.82, 0.26 and 23 in terms of bias, CV and RMSE, in terms of correlation Ensemble perform best which 00.7. Performance evaluation of RCM output show that, CCNMR simulates rainfall over most stations better than other RCMs irrespective of the driving GCM. Statistical agreement between simulated and observed flow data during the calibration periods resulted in a high agreement using R2, NSE and BIAS with the result of 0.84, 0.83 and 8.3% respectively. The finding of climate scenario show that, the maximum increment and decreasing precipitation in January and December was change 5e % and (23%) respectively. Tmax and Tmin showed an increment of annual average temperature of by 1.4 0C and 0.32 0C with 2040s scenarios respectively. Due to this climate change, 38 % of streamflow was increased in the month of August and the peak flow was reduced from 38% to 4% in the month of August to September. At the same time, the response of streamflow due LULC reveal that, the annual change in stream flow was decreased by -13.5%. The streamflow in mean wet season, small rain season and dry season due to LULC was -14%, 11% and -6% respectively. Finally, the total increases in mean annual streamflow due to future climate change were 27% while the total decrease change in annual streamflow due to Land use Land cover in mean was (-12%). The predicted changes in streamflow will have implications for water supply, flood control and stormwater management. Therefore, a comprehensive strategy of low impact developments, smart growth, and open space is critical to handle future changes to watershed systems.