Investigating the Effect of Bukan's Dam Construction on Hydrological Indices of Zarrinehrood River Based on the Flow Duration Curve

The aim of this study was investigating the impacts of Bukan's Dam construction on hydrological indices based on the Flow Duration Curves (FDCs) of the Zarrinehrood River during the pre (1955-1971) and post-dam (1972-2011) construction periods. For this aim, nineteen hydrologic indices were calculated in four groups of Peak Flow, Flow Duration, Low Flows and Flow Variability. In this regard, the Flow Duration Curves were plotted for both pre and post-dam construction periods. Based on the results, the values of 1-day maximum flow and the average of daily flow in the post-dam construction period decreased by 13% and 7.5%, respectively. However, the values of the index for 1-day minimum flow in the post-dam period increased by 4.7 percent. The results showed that at 50% of the flow duration time in post dam construction period the amount of discharge was increased 40%, which related to the impact of the dam on the flow of the Zarrinehrood River. The average magnitude of the rising rate relative to the average flow discharge in the pre and post periods of the dam were 97.71 and 79.18 cubic meters per second respectively, which indicated a 18% decrease in the flow of river flooding during the period after the dam construction. In the post-dam period, the average amount of discharge increased in summer season. In conclusion, the construction of the dam had reduced the flood variation related indices and increased the indices of the flow related to the duration components.