Today, global climatic issues and the water security problems resulting from the increasing water demand for hydropower and agricultural purposes from the rivers Tigris and Euphrates, in the Middle East, are quite important. The Snowmelt Runoff Model (SRM) was applied to the Karasu basin located in the upper Euphrates River drainage basin, in order to simulate and forecast the runoff from snow melting. A second study covered the application of the hydrological model SLURP-11 at a smaller scale. In combination these would enable early prediction of runoff from rainfall and snowmelt using snowmelt runoff estimation models coupled with Remote Sensing (RS) and Geographic Information System (GIS) technologies. The final aim of this study is to compare the results of the models SRM and SLURP, although applied on basins of different scales. Finally, conclusions are made about which kind of hydrological models are suitable for different basin characteristics and sizes.