Document Type : Research Paper
Author
Soil Conservation and Watershed Management Research Institute, Tehran, Iran
Abstract
Flood spreading systems are among the effective methods for water resources management in arid and semi-arid regions, playing a key role in artificial groundwater recharge and flood control. However, river morphological changes, sediment deposition, deterioration of diversion structures, and upstream dam construction can reduce their efficiency. This study investigated the hydraulic performance of the Cheskin flood spreading system in Qazvin Province, Iran, focusing on the diversion structure and water intake conditions from the Haji Arab River.
Topographic, meteorological, hydrological, and field data were collected and analyzed. Effective sub-basins supplying the flood spreading system were identified, and river discharge under conditions with and without the Balakhanloo Dam was simulated using the HEC-HMS hydrological model. A two-dimensional hydraulic model was then developed in HEC-RAS using a high-resolution digital elevation model derived from UAV imagery and calibrated based on a historical flood event.
The results showed that destruction of the grade control structure (spillway/weir), riverbed morphological changes, and the construction of the Balakhanloo Dam have significantly reduced the water diversion capacity of the system. Even under high-flow conditions, efficient diversion into the supply canal is not achieved. Scenario simulations indicated that reconstruction of the structure based on the original design could provide the safe conveyance capacity of the canal only when flow releases from the Balakhanloo Dam are available. In addition, optimization of the spillway geometry from a simple to a compound cross-section increased diversion efficiency by 35% to 270% within the discharge range of 0–189 m³/s.
The findings demonstrate that redesigning the diversion structure according to current watershed and hydrological conditions can substantially improve the performance of the Cheskin flood spreading system and support sustainable water resources management in arid and semi-arid regions.
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