Determine and Design Range of Optimal Environmental Flow Zarin-Gol River by Investigation the Hydromorphological Characteristics, Hydrological Regime and Habitat Suitability Simulation Ecohydraulic Model

In the studies of water resources sustainability and development planning in the watersheds, ecological values and continuance life cycle of the river ecosystems should be recognized. The natural flow regime, plays a key role in protecting river habitat components and biodiversity formation. For this purpose, in the present study, with step-by-step measuring and calculating the environmental flow of the Zarin_Gol River in Golestan province and using hydrological methods of Tennant, Tessman, Texas and Ecodeficit , the sustainable ecological conditions were studied and target fish habitat analysis with Ecohydraulic Habitat Physical Simulation Model (PHABSIM) compared. The results showed that by performing hydraulic simulation and analysis of habitat discharge-physics time series using curves Suitability Index, range of flow regime required to provide habitat ecological potential Paracobitis hicanica was between 0.85 to 4.42 m3/s, with Mean Annual Flow of 1.73 m3/s (equivalent 80 percent of natural stream of the river), It should have existed in inside the Zarin_Gol River. The flexibility and effectivenessof the flow regime of the hydrological methods of Tannant, Texas and Tessman were not sufficient for the conservation and restoration of the studied river habitat. But Ecodeficit method, by providing environmentally friendly flow statistics, while providing in-stream needs, well describes the hydrological changes of the Zarin_Gol River flow regime. According to the results, the ecological optimum flow regime assigned by habitat simulation method is able to protect the natural flow regime for preserving the ecological values of the river, Proper performance of river habitats and preservation of morphological conditions of river bed. The methods used in this study and the obtained results, provide a valuable reference for water resources planning and ecosystem protection in rivers.