Curve Number (CN) Calculating and Zonation of SubbasinsCase study: Ahar Chay Basin

One of the most important Physical factors in basin is the time of concentration. Bacause,there is the curve number (CN) factor in calculating the time of concentration,so that is nessecity for some researches in soil penetration, landuse and surface savecoefficient filds.In this paper, the mentioned items are calculated which contain sampling all of casesurface and determining the soil penetration. Next stage contains recognizing soilpenetration Zonns, landuse of basin and those maps.Presenting the hypothesizes and subbasins recognizations were the next stages thatlead to calculating CN amount in surface basin and CN polygon maps.Finally, amount of time of concentration of basin and subbasin (by hour) based onsoil conservation service(SCS) relation are calculated that are useful in hydrologicalcalculations.