Application of SCS-Curve Number Method to estimate Runoff using GIS for Gali-Bandawa Watershed

In any hydrologic study, the most important parameter is runoff which necessary for designing hydraulic structure, and determining risk of flood. As there a scare in availability data many sites, hydrologists have developed indirect methods to determine accelerate program watershed management conserving developing water resources management. Many are used estimate runoff; Soil conservation curve number (SCS-CN) method widely gives reliable result compared with other methods. The present study aims calculate surface depth depending on SCS-CN using Geographic information system (GIS). For this Gali-Bandawa Duhok, north Iraq has been selected, geographical area about 92Km2 average annual rainfall around 620mm, weighted CN 76. results show that 70mm, volume from same 6470360 m3. amount represents 11.4% total rainfall. This approach could be applied Iraqi's watersheds planning various measures.