development and application of a decision support system for flood production and control using hydrological flow and reservoir simulation models

This study employs hec-hms and hec-ressim software to simulate flood events and optimize reservoir operations in the dez river watershed, iran. the hec-hms model was calibrated using 21 historical flood events, with key parameters—including rainfall losses, unit hydrograph methods, and flood routing (using the muskingum method)—adjusted to minimize error between observed and simulated discharge. results reveal significant variations in hydrological response across sub-basins: dorood and dorood 3 exhibit slow runoff due to large drainage areas (3449 km² and 2655 km²) and low infiltration rates (0.91–1.1 mm/hr), while tang panj basins show rapid response (lag times of 2.0–2.5 hr) and high infiltration (2.19–4.4 mm/hr), likely due to steep terrain and permeable soils. for reservoir management, hec-ressim was used to simulate dez dam operations under current and elevated water level scenarios (352–362 masl), prioritizing downstream demands (irrigation, municipal supply, and ecological flows). seasonal allocation patterns were identified, with peak diversions in june–july (320–324 mcm) for agriculture and minimal releases in winter (87–96 mcm). raising the dam height by +8m (360 masl) optimally balanced flood control (22–25% storage increase) and drought resilience, though +10m required costly infrastructure upgrades. the study underscores the trade-offs between storage capacity, operational flexibility, and environmental needs, providing a framework for adaptive water resource management in semi-arid regions.