Browsing by Author "Mahtsente, Tibebe"

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    Runoff Estimation and Water Management for Holetta River, Awash Subbasin, Ethiopia
    (Addis Ababa University, 2013-06) Mahtsente, Tibebe; Assefa, Melesse (PhD); Dereje, Hailu (PhD); Birhanu, Zemadim (PhD)
    The hydrology of Holetta River and its seasonal variability is not fully studied. In addition to this, due to scarcity of the available surface water and increase in water demand for irrigation, the major users of the river are facing a challenge to allocate the available water. Therefore, the aim of this research was to investigate the water availability of Holetta River and to study the water management in the catchment using Geographical Information Systems (GIS) tool, statistical methods, and hydrological model. The rainfall runoff process of the catchment was modeled by Soil and Water Assessment Tool (SWAT). According to SWAT classification, the watershed was divided in to 6 subbasins and 33 hydrological response units (HRUs). The only gauged subbasin in the catchment was subbasin one that is found in the upper part of the area. Therefore, sensitivity analysis, calibration, and validation of the model was performed at subbasin one and then the calibrated model was used to estimate runoff at the ungauged part of the catchment. The performance of SWAT model was evaluated by using statistical (coefficient of determination [R2], Nash-Sutcliffe Efficiency Coefficient [NSE] and Index of Volumetric Fit [IVF]) and graphical methods. The result showed that R2, NSE, and IVF were 0.85, 0.84 and 102.8 respectively for monthly calibration and 0.73, 0.67 and 108.9 respectively for monthly validation. These indicated that SWAT model performed well for simulation of the hydrology of the watershed. After modeling the rainfall runoff relation and studying the availability of water at the Holetta River, the water demand of the area was assessed. The survey form was used to identify information, which includes the number of Holetta River consumers, major crops grown by irrigation and the total area coverage. CropWat model was used to calculate the irrigation water requirement for major crops. Based on the result of CropWat model and survey analysis, the irrigation water demand for the three major users of Holetta River was calculated. The total water demand of all three major users was 0.313, 0.583, 1.004, 0.873 and 0.341 MCM from January to May respectively. The available river flow from January to May was taken from the result of SWAT simulation at subbasins 2,3,4 and 5. The average flow was 0.749, 0.419, 0.829, 0.623 and 0.471 MCM from January to May respectively. From the five months, the demand and the supply showed a gap during February, March and April. This indicated that there is shortage of supply during these months with 0.59 MCM. Therefore, in order to solve this problem alternative source of water supply should be studied and integrated water management system should be implemented.