Determination of Optimal and Desirable Environmental Flow Release from Latian Dam reservoir with Consideration of Ecohydraulic, Hydrological and Hydromorphological Characteristics to Protect the Habitat of the Jajrood River

A good understanding of the river natural flow regime plays an important role in many hydrological studies. Such studies also quantify the environmental flow, the basis for the conservation of river fish habitats and aquatic ecosystems, and need to be recognized in the policies and decisions of water resource development plans and their inclusion in watershed management plans. In the present study were calculated and evaluated hydrological methods such as Tennant, Aquatic Base Flow, Arkansas and Range of Variability Approach (RVA) to estimate the minimum ecological flow and Habitat Simulation model to preserve the ecological potential of the Jajroud River. In this regard, based on the research framework, after hydrological analysis and field observations, a habitat suitability model was developed for the target species and finally, habitat simulation was performed by combining ecohydraulic and hydrological indices of flow and analysis of flow - habitat physics time series using suitability curves. Based on the results, to maintain optimal conditions and protect the ecosystem components and habitat of biological communities, using the River2D model range of flow regime required to provide habitat ecological potential Squalius namak, it should be located along the Jajroud River between 1.24 to 18.55 m3/s, with mean annual flow 5.91 m3/s (86.7 Percent Mean Annual Flow). It is noteworthy that the Tennant methods should be used with caution in summer because this method offers between 9 and 96 percent of the mean annual flow. Finally, it was concluded that other methods of providing environmental flow provide values above 25% of the mean annual flow, which provide better protection of the stream for aquatic habitats. In contrast, the River2D ecohydraulic model can provide a general idea of habitat suitability across different river basins with respect to changes in natural flow regimes and the achievement of ideal and optimal flow conditions.