Single storms are the most restore water at the water management especially in arid and semiarid. Therefore, single storm estimation is the important step in risk management. This study, single storm estimated by GSDM model. So, the date used include: Meteorological data, DEM and water value in basin Jahanbin. In the GSDM model should divide basin to two region smooth and rough, Moisture Adjustment Factor (MAF), Elevation Adjustment Factor (EMF) and calculated humid in dew point 28 cº. The results shows, that estimated rainfall amount by GSDM model are the better than. The estimated rainfall by GSDM model is between 126mm in smooth region and 350mm in rough region. The compare is between estimated rain fall and record maximum rain (Jouneghan station) shows that amount estimated by GSDM model is suitable.