The article explores two methods of spatial interpolation, IDW and Kriging, to map the distribution of runoff coefficient in the Karun River basin in Iran. IDW is suitable for interpolating values from a large number of evenly distributed points, while Kriging produces smoothed contour lines of hydrological characteristics that summarize information across the area. The comparison between actual and interpolated values showed that IDW is effective for many evenly distributed points, while Kriging provides smoothed contour lines of hydrological characteristics.