Expansion of agriculture, urbanization, deforestation and the day to day activities of mankind resulted to temporal and spatial change in land use land cover have affected water flow pathways and water balance. The understanding of Land use land cover change is of fundamental importance for environmental monitoring, and governmental decision making. The aim of this study was to Investigation the Impact of Land use Land cover dynamics on streamflow. ArcSWAT and QGIS plugin of MOLUSCE were used for modeling, and Landsat 5 TM 1995, Landsat 7 ETM+ 2007 and Landsat 8 ETM+ level 1 images were gathered from satellite. And ERDAS 2014 software was used for image classification by Maximum Likelihood Algorithm of Supervised Classification. Images were classified into five classes such as cultivated land, Forest, Grassland, Shrubland, and Water. Results shows that the cultivated land covers in 1995, 2007 and 2018 by 39%, 46.81%, and 52.45% respectively. The performance of the SWAT model was evaluated through sensitivity analysis, calibration, and validation. Twelve sensitive flow parameters were identified and used for model calibration as well as validation. The NSE and R2 for monthly flow calibration; were 0.73, 0.79 respectively and the monthly flow validation were 0.63 and 0.70 respectively. From this land cove change simulated mean monthly peak discharge of the three Land use land cover changes 1995, 2007 and 2018 land cover map were 59.30, 64.82 and 69.04 m3/s respectively. The simulated peak discharge had a variation due to Land use land cover change from the last 24 periods. The future of Land use land cover for 2027 was predicted by used Cellular Automata Simulation in MOLUSCE /QGIS/.The result also suggests a significant increase in the cultivated land and Forest. The Cultivated land was increased by 6.97% and Forest increase by 0.89% on the initial period and have also impact on streamflow of Upper Gilgel Abbay watershed. The simulated mean monthly stream flow of in 2027 is 73.02 m3/sec. Due to the change of Land use land cover shows a significant impact on the streamflow. Therefore, Government and planners should take responsibility for the change of land cover effects on the river flow.