Quantitative Changes and Statistical Comparison of River Flow Hydrological Indicators after the Construction of Yamchi Dam, Ardabil, Iran

The purpose of this research was to analyze the quantitative changes and statistical comparison of the hydrological river flow indices due to dam construction in the upstream and downstream hydrometric stations during 2004-2013 period at the Ardabil Province. For this purpose, the flow duration curve (FDC) and 30 hydrologic indicators in the upper and lower stations of Yamchi Dam were calculated. The statistical analysis was performed against calculated indices using paired t-test and FDC analysis. According to the results, the mean high-water discharge in Nir (upstream) and Poleh Almas (downstream) stations was calculated to be equal 1.43 and 1.73 m3/s, indicating no significant differences between these stations in term of high-water discharge. Therefore, the maximum and minimum flow and discharge rates of 5, 85, 90, 95 exceedance probabilities and Q90/Q50, slope, standard deviation and Lane Index had significant difference under the effect of dam construction and the mean discharge was reduced. Moreover, indicators of zero discharge, zero percent, low flow, high flow, normal, median, mode, 25, 35, 45, 50, 65, 75, 85 exceedance percent and discharge of Q90/Q50 experienced a significant difference. The results showed that the river regime discharge in Pole-Almas station is affected by the Yamchi Dam and the average discharge had reduced. In addition, there is a significant difference between hydrological indicators of minimum and maximum discharge and FDCs at studied stations. Therefore, evaluating the changes in river regimes provides the possibility of making sound management decisions in river flow utilization.