Abstract
Flood forecasting has become necessary for dam management during extreme hydrological events. The lack of streamflow data in ungauged watersheds of arid and semi-arid regions makes the assessment of water resources di cult. In this paper, the Hydrologic Modeling System developed by the Hydrologic Engineering Center (HEC-HMS) was applied to the Oued El Hachem watershed. Calibration and validation of the model have been performed, taking into account the lag time and the curve number CN that is expressed as a function of soil group, land use and antecedent runo condition. The model was evaluated on the basis of the coe cient of determination, the Nash Sutcli e E ciency (NSE), and the percentage di erences between peak and volume. Performance indices of calibration showed a good agreements between observed and computed flows. The validation of the model has given satisfactory results. The calibrated model can be used to manage the dam of Boukerdane during extreme rainfall events by forecasting the induced hydrographs from which adequate procedures will be operated in order to ensure the safety of the dam against possible overtopping.