Land use land cover change (LULC) is very significant issues in terms of global dynamics and their responses to hydrologic features and soil & water management of a watershed, because it has a great effect on stream flow. This study aims to evaluate the impact of land use /cover change using SWAT model. The land use/cover data were obtained from Land Sat 8 and processed by ERDAS IMAGINE 2014 software through maximum likelihood of supervised classification techniques. Four land use land cover maps of 1988, 1998, 2008 and 2018 were prepared and these data were used for base map, model calibration and change study respectively. From the result the classification of image indicated that, the transition from grass, forest and shrub land to cultivated, bare and urban land. The increased class cultivated land by 28.87 %, bare land 31.84% and urban 103.33%, while decreased class forest land by 0.2 %, shrub 61.14% and grass 35.35%. A hydrological model, SWAT was used to simulate LULC effects on the hydrological responses of wanka watershed. The simulated stream flow results were utilized to analyze seasonal variability of stream flow due to land use land cover changes. The performance of the SWAT model was evaluated through sensitivity analysis, calibration and validation. The calibration result shows good agreement between monthly observed and monthly simulated stream flow having R2 and NSE values of 0.88 and 0.86 respectively. The validation result shows good agreement between monthly observed and monthly simulated stream flow having R2 and NSE values of 0.76 and 0.86 respectively. The result of this study indicated that the mean seasonal stream flow were increased from 10.84 to 16.44 m3/s by 51.66 % for wet season and decreased from 0.89 to 0.431 m3/s by 55.4 % in dry season over 20 year’s period of flow. From the overall results of the study, it is possible to conclude that land use land cover change has been influencing the stream flow or dry season flow of the catchment.