Ecosystems Protecting of Gharasoo River based on Regulation of Environmental Flow Regime using Hydrological Methods

Due to the increasing deterioration of river life systems because of human intervention, droughts and climate change, the recognition of the environmental flow in planning water resources development studies to maintain the health of it is necessary. The main objective of in this research is to implementation and assessment the methods of Tennant, Flow Duration Curve, Eco deficit, Aquatic Base Flow, Flow Duration Curve shifting (FDC Shifting) and Desktop Reserve Model (DRM) in estimating the environmental flow of Gharasoo River in different months of the year in the range of studies of Siahab hydrometry station to entrance to Gorgan Gulf in order to conservation and restoring of the above river. In the present study by comparing the results of suggested values of environmental flow in Gharasoo River were determined to be estimate Tennant method 0.57 m3/s for April to September and 0.19 m3/s for October to March, Flow Duration Curve method in conditions of relatively suitable (Q90) and suitable (Q75) was respectively 0.17 and 0.393  m3/s, Aquatic Base Flow method 0.57 m3/s, FDC Shifting method in relatively modest conditions with an annual average of 0.94 m3/s, Eco deficit method 0.88 m3/s and in class B DRM model 0.69 m3/s. Accordingly, by providing the ecological regime of the Gharasoo River, it is possible to maintain proper conditions for maintaining the ecosystem health using FDC Shifting method in C management class (48.5 percent of natural stream of the river).