Hydraulic Engineering

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/69

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    IMPACT OF CLIMATE CHANGE ON AGRICULTURAL WATER DEMAND: THE CASE OF BILATE RIVER CATCHMENT
    (Hawassa University, 2019-10-27) ZEKIWOS KEBEDE KARISA
    Climate change has impact on agricultural water demand by affecting the different climate variables such as temperature and rainfall. This study was carried out to detect the impact of the climate change on agricultural water demand under different time horizon to prevent vulnerability to climate change at Lower Bilate River sub-basin. The data used in this study were collected from National Meteorology Agency of Ethiopia, Ministry of Water, Irrigation and Electricity. Simulated climate data were obtained with using single climate model ICHEC-EC EARTH, Precipitation and temperature time series of historical and projected time period. The scenarios used were from the Eth_CORDEX_Grids archive based on RCP4.5 and RCP8.5 Scenarios. The trend analysis for the last 32 years, indicated that the impact of the climate change to changes in long-term maximum and minimum temperature is increased by 0.0395o c and 0.1380 c respectively and changes in precipitation is by the factor of the -0.83, the prediction analysis indicates that precipitation at the study area will be -35.71% and -40.18% for the year 2048 and 2080 respectively from RCP4.5 Scenarios. Whereas, based on RCP8.5 Scenarios the change in the same order will be -48.90% and -60.11%. As a result the change is expected in agricultural water demand for the selected crops at specific study area. The average irrigated agriculture water demand of selected crops Tobacco and cotton are found to be 19.01Mm3. However, this value is not kept constant as a result of the change in climate that for future time period (2017-2048) and (2049-2080) found to be 24.01Mm3 and 25.01Mm3 respectively for RCP4.5, and in case of RCP8.5 is found to be 25.33Mm3 and 28.36Mm3 respectively. Whereas, the Rain fed agriculture water demand for the crops maize and haricot bean are estimated 87.98Mm3 at the study area. As a result, the change in climate computed as 86.65Mm3 and 104.28Mm3 for the period of 2048 and 2080 respectively for RCP4.5 Scenarios, whereas based on RCP8.5 Scenarios the change will be 100.39Mm3 and 125.42Mm3 respectively
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    IMPACT OF CLIMATE CHANGE ON THE HYDROLOGY OF UPPER BLUE NILE RIVER BASIN: A CASE STUDY IN TANA SUB-BASIN, ETHIOPIA
    (Hawassa University, 2020-11-06) SURAFEL ARAGAW LAMESGIN
    Climate change is one of the serious issues in the word including developed and developing countries like Ethiopia. Tana Sub-Basin is located in the upper Blue Nile River basin . The aims of this study was to evaluate the impact of climate change on the hydrology of Upper Blue Nile River basin of Tana sub-basin in the northwest of Ethiopia. Dynamically downscaled climate model precipitation and temperature outputs were obtained from CORDEX-Africa program RCP4.5 and RCP8.5 by Regional Climate Model. The climate data has significant bias and bias correction was done by using CMhyd tool before used as input to the impact analysis. The analysis was performed in two future projection, 2020-2049 and 2050-2079 considering the reference baseline period 1988-2017 with both RCPs. Minimum temperature changes for RCP 4.5 raised by 0.26°C to 1.10°C and 0.45°C to 2.77°C, and for RCP8.5 0.15°C to 1.58°C and 1.02°C to 2.68°C Mean monthly minimum temperature change for 2020 – 2049 and 2050 – 2079. and Maximum temperature changes for RCP 4.5 and increase by 0.25°C to 1.6°C and 0.1°C to 1.91°C and for RCP 8.5 0.11°C to 1.92°C and 0.19°C to 2.17°C for 2020 – 2049 and 2050 – 2079 time periods with reference to the baseline periods respectively. And also, the mean monthly precipitation change will be increased and decreased by 2.09% to 23.95 % and 30.73% to 47.46% for both RCP4.5 and RCP8.5 scenarios respectively. The SWAT models were used to assess the streamflow response to climate change. Calibration and validation of the model output were performed by comparing simulated streamflow with observed flows from Tana Sub Basin (Blue Nile River outlet at Bahirdar gauging station) for the periods 1988-2001 for calibration and 2002-2008 for validation using SWAT-CUP(SUFI-2). The model calibration and validation result shows R2 and NSE of 0.87 and 0.84 and 0.61 and 0.6 during calibration and validation respectively. Finally, climate change impact on monthly streamflow was evaluated by relating base period stream flow with the future flows for the 2020-2049 and 2050- 2079 for both RCP4.5 and RCP8.5 scenarios. The future streamflow result shown increasing and decreasing change for both RCP4.5 and RCP8.5 scenarios. Hence, the increased and decreased stream flow in the basin may have a significant contribution for the sustainability of existed and undergoing water development projects