Estimating the Environmental Flow Requirement in Downstream of Hydroelectric Power Plant of Zivkeh- Piranshahr

For river management, it is essential to allocate a certain amount of water to sustain life and ecology of the river. In recent years, the environmental flow requirement (EFR) of river has been posed as a new competitor of basin water consumptions aside domestic, agriculture, and industry sectors. In this research, different hydrological criteria of EFR was probed in downstream of Zivakeh hydroelectric power plant. Five hydrological methods such as the probability of 95% and 90% of flow duration curve, Montana, 1SD, monthly distribution probability of drought with the return period of 25 years, and 1, 7, and 30 days with different return periods such as 1Q10, 7Q10, 30Q5 were used. For analysis 22-years daily data from the water year of 1372 to 1393 were used. The results indicated that the monthly average of the five methods varied from 0.48 to 3.13 m3/s that equals 35.5 MCM and 25% of mean annual runoff (MAR) of the river. These values for EFR show good agreement with the common indices.