Evaluating the effectiveness of watershed management practices in reducing runoff, erosion, and sediment yield is a key component of sustainable watershed management. This study aimed to assess the impacts of mechanical watershed management measures on peak flood discharge and sediment production in the Alkhalaj watershed, East Azerbaijan Province, Iran, using the HEC-HMS and MPSIAC models. Peak flood discharges were simulated for different return periods under pre- and post-treatment conditions using the HEC-HMS model. In addition, changes in erosion and sediment yield were evaluated using the MPSIAC model. The results indicated that the implemented conservation structures significantly reduced peak flood discharge in all sub-watersheds. The highest reduction was observed for the 2-year return period, reaching 89.28% in the Alkhalaj sub-watershed and 88.46% in the Tikmehdash sub-watershed, while the lowest reduction (32.50%) occurred in the Ghizil-Ahmad sub-watershed. The effectiveness of the measures decreased with increasing return period. Hydrograph analysis showed a reduction in peak flow and an increase in time to peak after implementation of watershed management measures. The MPSIAC results revealed an overall reduction of 35.20% in erosion and sediment yield across the watershed, with the highest reduction (38.79%) recorded in the Ghizil-Ahmad sub-watershed. Overall, the findings demonstrate that mechanical watershed management measures play a significant role in runoff control, erosion reduction, and moderation of watershed hydrological response, and can therefore be considered an effective strategy for sustainable watershed management in semi-arid regions.