The changes in environmental flow components of a permanent river due to the construction of a large reservoir dam

Hydrological regimes are crucial for river ecosystems, which depend on flow patterns. Dams disrupt these regimes, creating variations in river systems, requiring management to analyze and assess flow changes. This study aims to assess the impact of the Shahid Kazemi Dam construction on the flow regime and environmental flow components of the Zarrineh-Roud River, a permanent river. The findings of this research can contribute to a better understanding of the changes in natural flow components influenced by river flow regulation. In this study, 33 hydrological parameters, categorized into five statistical groups, were used as indicators of hydrological change at the Sarighamish hydrometric station. The IHA software was utilized to evaluate changes in the Zarrineh River's flow from 1955 to 2015, comparing pre- and post-dam periods. Additionally, the independent samples t-test was employed to assess river flow changes. The results showed that hydrological indices at the study station were altered due to dam construction, with some indices increasing while others decreased. The construction of the Shahid Kazemi dam has caused substantial changes in environmental flow components (EFCs) at the Sarighamish station, particularly in monthly low flows, where October low flow decreased from 20.65 to 4.2 cms. High flow pulses were also affected, with the high flow peak reducing from 65 to 56 cms, though the duration of these pulses increased significantly from 3.25 to 9.5 days, indicating prolonged high flow conditions post-dam. Significant differences in river flow components at the Sarighamish station were observed after the dam's construction. March and April showed large increases (70.97 and 86.27), while October and July saw notable decreases (- 19.68 and - 21.38), highlighting the dam's impact on seasonal flow patterns. To preserve the Zarrineh River's ecological conditions, water management must regulate the Bukan Dam's flow regime to align post-dam hydrological indices with the natural flow variation.