The hydrology of Holetta River and its seasonal variability is not fully studied. In addition tornthis, due to scarcity of the available surface water and increase in water demand forrnirrigation, the major users of the river are facing a challenge to allocate the available water.rnTherefore, the aim of this research was to investigate the water availability of Holetta Riverrnand to study the water management in the catchment using Geographical Information Systemsrn(GIS) tool, statistical methods, and hydrological model. The rainfall runoff process of therncatchment was modeled by Soil and Water Assessment Tool (SWAT). According to SWATrnclassification, the watershed was divided in to 6 subbasins and 33 hydrological response unitsrn(HRUs). The only gauged subbasin in the catchment was subbasin one that is found in thernupper part of the area. Therefore, sensitivity analysis, calibration, and validation of the modelrnwas performed at subbasin one and then the calibrated model was used to estimate runoff atrnthe ungauged part of the catchment. The performance of SWAT model was evaluated by usingrnstatistical (coefficient of determination [R2], Nash-Sutcliffe Efficiency Coefficient [NSE] andrnIndex of Volumetric Fit [IVF]) and graphical methods. The result showed that R2, NSE, andrnIVF were 0.85, 0.84 and 102.8 respectively for monthly calibration and 0.73, 0.67 and 108.9rnrespectively for monthly validation. These indicated that SWAT model performed well forrnsimulation of the hydrology of the watershed. After modeling the rainfall runoff relation andrnstudying the availability of water at the Holetta River, the water demand of the area wasrnassessed. The survey form was used to identify information, which includes the number ofrnHoletta River consumers, major crops grown by irrigation and the total area coverage.rnCropWat model was used to calculate the irrigation water requirement for major crops.rnBased on the result of CropWat model and survey analysis, the irrigation water demand forrnthe three major users of Holetta River was calculated. The total water demand of all threernmajor users was 0.313, 0.583, 1.004, 0.873 and 0.341 MCM from January to Mayrnrespectively. The available river flow from January to May was taken from the result of SWATrnsimulation at subbasins 2,3,4 and 5. The average flow was 0.749, 0.419, 0.829, 0.623 andrn0.471 MCM from January to May respectively. From the five months, the demand and thernsupply showed a gap during February, March and April. This indicated that there is shortagernof 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 managementrnsystem should be implemented.