Changes in Environmental Flow Components under the Effect of Sabalan Dam in the Qarehsou River of Ardebil Province

Sustaining environmental flows to preserve biodiversity of aquatic plant and animal species, as well as constancy of water for human communities, is essential in many river ecosystems. On the other hand, hydrological changes caused by the dam and its related environmental problems have provoked many concerns for hydrologists, ecologists and policymakers. Therefore, the main aim of this research was to study the rate of change in the Environmental Flow Components (EFCs) caused by the construction of Sabalan Dam in the Qarehsou River of Ardebil at stations of Arbabkandi and Dostbeiglou (before and after Dam) using IHA Software7.1 during the time period of 2005-2014. For this purpose, the values of 34 environmental flow parameters were estimated at each hydrometric station. Consequently, changes in the parameters of the environmental flow discharge were investigated in four groups of Extreme Low Flows, Low Flows (Base flow), High Flow pulses, and Floods events. The diagram below shows the parameters of minimum flow, peak flow and small flood. Based on the results, the frequency of Extreme Low Flows at the Dostbeiglou station had a 59% increase with respect to Arbabkandi station. On the other hand, the peak flow component showed more balanced nature in Dostbeiglou station after the dam, which can be related to the regulating effect of dam on high flow and balancing outflow in downstream reaches. The Peak flow, Duration, Timing and Frequency of small flood events had decreased in Dostbeiglu Station compared to the Arbabkandi with amount of 27, 78, 68 and 17 percent, respectively. Also, the peak and frequency of large floods had decreased at Dostbeiglu station with amount of 26 and 50%, compared with the observed flood events at the Arbabkandi station which located before the Sabalan dam.