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Subject: search.filters.subject.Gidabo watershed

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    ASSESSMENT OF WATER BALANCES USING SWAT MODEL AND AGRICULTURAL WATER DEMAND ANALYSIS OF GIDABO RIVER CATCHMENT, RIFT VALLEY BASIN, ETHIOPIA
    (Hawassa University, 2020-07-18) CHALA TADESSE
    To use water resources sustainably, it is important to understand the quantity of water resource spatially and temporally. The work presented here attempts to model water balance of one of Gidabo sub-watershed of Ethiopian Rift Valley Basin using the Soil and Water Assessment Tool (SWAT. Statistical model performance measures, the coefficient of determination (R2 ) and Nash-Sutcliffe Efficiency (NSE) were used to evaluate the correlation between the observed and simulated monthly stream flow. The result shows an acceptable performance of SWAT model in simulating the watershed hydrology as evidenced by the NSE value of 0.79 and R2 value of 0.80 at calibration (using data from1990-2009) and NSE = 0.71 and R2 =0.82 at validation (using data from2010- 2014). In terms of water balance components, the long-term annual precipitation is found to be in the magnitude of 1435.58 mm; whereas the surface runoff; total water yield; and actual evapotranspiration, are estimated as 62.20; 1189.73, and 228.40 mm respectively. In order to link the water balance estimation with the local agricultural water demand, wheat and potato are selected for they are common crops for irrigation in the watershed. While taking the month of March, which is the month of maximum agricultural water demand (11.6 m 3 /s), the watershed is found to be water-surplus as indicated by the water availability of the critical month (12.22 m3 /s) to be higher than the demand. This research implies that the use of models in supporting decisions related to water resources development and management is paramount important to understand how the system functions
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    IMPACT OF CLIMATE CHANGE ON WATER AVAILABILITY IN GIDABO WATERSHED, SOUTHERN ETHIOPIA
    (Hawassa University, 2020-04-24) ADANE MEZEMIR MENIGISTU
    Climate change significantly affects many hydrological systems, which in turn affects the water resource and the flow of rivers. The aim of this research was to investigate the impacts of future climate change on the water availability of the Gidabo watershed, which is one of the Ethiopian rift Valley sub-basins. Dynamic downscaling model was used as a representative concentration pathway (RCP) scenario for the daily precipitation, maximum and minimum temperature in the watershed. The large-scale climate variables for the RCP4.5 and RCP8.5 scenarios obtained from the Hadley Global environment model through CORDEX-Africa data outputs of HadGEM2-ES were selected under representative concentration pathway. The analysis was performed in two future projection of 2018- 2047’s and 2048-2077’s with baseline period of 1988-2017. Results showed that the average annual max/min temperature will increase by 1.23oC/1.26oC and 2.64oC/3.27oC (for 2018-2047) and by 2.57oC/0.23oC and 3.542oC/2.3oC (2048-2077) for RCP 4.5 and RCP 8.5 respectively. Average annual rainfall decreased 69.19mm and 72.3mm at RCP4.5 and RCP8.5 for (2018-2047) respectively and decreased 79.02mm and 85.12mm at RCP4.5 and RCP8.5 for (2048-2077) respectively. The SWAT hydrological model was used to simulate streamflow together with other water balance components after sensitivity analysis, calibration and validation of the model. The results indicated that water yield decrease by 21.8% and 23.9% of the rainfall in the case of RCP 4.5 and RCP 8.5 respectively. On the other hand, the trend test result on gaged data showed the presence of a no statistically significant trend in the precipitation and significant trend in the minimum temperature at most of the stations.