Estimation of environmental flow of the Balikhlochai River and evaluation impact of Yamchi dam operation on hydrological and environmental regime of the river

The provision and allocation of environmental rights of rivers, should be considered as a necessity in the sustainable management of the country's water resources, to protect the water resource ecosystem and the ecosystems associated with these resources, such as wetlands and lakes. In this research, over a 44 year period (from 1970 to 2013), the environmental flow of the Balikhloochai River, was studied using Tennant, Tessmann and FDC methods. Using IHA software, the effect of construction and operation of the Yamchi dam on hydrological and environmental changes, were investigated. Results showed that the Tennant method calculate the river flow between 1.96 to 3.27 m3/s to keeping the river flow regime at the optimum range for all months of the year, while Tessmann method calculate it 1.31 m3/s. The results of the FDC indicate that for the protection of the river in suitable and relatively suitable conditions, the flow rate of 2.95 and 2.46 m3/s was required, respectively. It was found that Dam operation has influenced downstream hydrological and environmental parameters. The extent of these effects on hydrological parameters such as Magnitude of monthly water conditions, Magnitude and duration of annual extreme water conditions, timing of annual extreme water conditions, and frequency and duration of high and low pulses status were 61.38% with moderate change degree. Also, despite the dam, 51.6% of environmental parameters such as monthly low flows, extreme low flows, small floods and large floods have changed.