In present study, the HEC-HMS model was employed to examine and simulate runoff within the Kardeh Dam watershed. WMS and ArcGIS software were utilized to extract the physiographic information of the basin, and the necessary parameters for rainfall-runoff modeling were determined. To evaluate the accuracy and performance of the model in simulating runoff, the SCS + Muskingum (SCSM) and CLARK + Kinematic wave (CLARKK) approaches were applied. The modeling results indicated that the peak discharge at the outlet of the Kardeh Dam basin using the SCSM approach (81.6 m³/s) is lower than that obtained from the CLARKK approach (96 m³/s). The computed runoff volume using the SCSM approach at the basin outlet was estimated to be 1190.9 m³. In the CLARKK approach, the runoff volume was approximately similar; however, the peak discharge differed, being approximately 14 m³/s higher than that of the SCSM approach. The peak inflow to the reservoir was 160 m³/s using the SCSM approach method and 140 m³/s using the CLARKK approach. In both methods,comparison of the observed and simulated hydrographs indicated that the SCSM approach provided greater accuracy in predicting the timing of peak occurrence. For the SCSM approach, the Nash–Sutcliffe efficiency coefficients were computed as 0.9 for sub-basin 3B, 0.4 for sub-basin 4B, and 0.6 for sub-basin 5B, demonstrating the appropriate accuracy of this method. The results revealed a reasonable agreement between the observed and simulated peak runoff discharges, although differences were observed in both the magnitude and timing of peak flows between the models.