Comparative assessment of environmental water requirements and river flow health in the Ghezel-Ozan River, Iran

Study Region: This study examines the Divandarreh-Bijar watershed, which covers an area of 5560.16 km² and through which the 180 km-long Qezlozan River flows, originating from the Chehel Cheshme Mountains. Study Focus: This study assesses the suitability of the Ghezel-Ozan River for the native fish Capote razii in western Iran by applying conventional hydrological methods, hydraulic techniques, and model-based habitat-suitability approaches, and by evaluating the flow regime using the Flow Health Tool. New Hydrological Insights for the Region: The main findings of this study are the following: (1) Capoeta razii has been identified as an ecological indicator species occurring in all types of mesohabitats; (2) The greatest fish diversity was found in the habitats of the run and riffle of the river rafts; (3) The deviation of the flow regime has increased considerably after 2012 as a result of the operation of the dams; (4) The EWRs ranged from 0.33 to 43.9 m3/s according to the different methods; (5) The Habitat Suitability model was the most representative of the environmental needs; and (6) To protect 75 % of suitable habitats, a minimum average flow of 10.09 m3/s is required. The best method to estimate environmental flows is to consider river health and the habitat requirements of native species.