Estimation of continuous daily runoff based on rainfall is quite difficult, mainly due to limited and unavailability of the records of climate. In present day, hydrological modeling is a vital tool for estimation of runoff in ungauged basins. In the present work, Rana, a typical ungauged watershed in the river basin of Mahanadi in Odisha, India, has been selected as the study area for hydrological modeling using SWAT (soil and water assessment tool), a semi-distributed model with a facility of Arc-View GIS (Geographic Information System) to calculate the surface runoff. The data sources used in the study for the computation of runoff were DEM, maps of LULC (Land Use and Land Cover) and soil and rainfall, temperature, relative humidity and solar radiation data. SWAT model divides the entire catchment into subcatchments which are subsequently categorized into HRUs (hydrologic response unit) based on the inputs of the maps of soil and LULC. SWAT model utilized SCS-CN (Soil Conservation Service curve number) method for the simulation of flow on daily basis for the study area. The result shows that discharge generated during the months of monsoon contributes maximum percentage toward annual discharge in Rana basin. Maximum monthly average discharge experienced in September whereas minimum monthly average discharge observed for the month of April. SWAT model is capable for the identification of the characteristics of runoff of similar types of sub-watersheds in basin Mahanadi, and by doing so precise investigation of water resources for whole basin Mahanadi can be possible.