River flow regime analysis through consecutive gauge stations: an indicator-based approach in Northwest Iran

This study aims at analyzing river flow regime in consecutive gauge stations by quantifying 33 indicators of hydrologic alteration, 34 environmental flow components (EFCs), and flow duration curve (FDC) in Qareh-Sou River in Ardabil province, Iran. The hydrological and EFCs–FDC were drawn seasonally for each gauge station. The Python cluster correlation matrix and Taylor diagram investigated indicator links with annual average discharge, while base flow index variations were explored through a three-variable diagram. Based on the results, the maximum daily flow components had an increasing trend, which attributed to the river flow aggregation. The rise rate values in Aladizgeh, Gilandeh and Samian stations were 0.20, 0.32 and 0.61, respectively, which indicated the increase of river flows in the downstream. Large flood peak from upstream to downstream stations was 8.63, 36.70 and 74.24 m3/s, respectively. The BFI values had a decreasing trend from upstream to downstream, while according the seasonal FDCs, in Aladizgeh, Gilandeh and Samian stations, discharge in spring and in 50% exceedance time was 0.49, 1.77 and 8.07 m3/s, respectively, along with an increase in seasonal flow in the downstream. In the upper reaches, there was no discernible trend in seasonal flow changes, suggesting limited human interventions, withdrawals, and water diversions. These findings offer valuable insights for water managers and local policymakers, providing a basis for implementing effective and sustainable strategies to handle flood flows and enhance environmental flow management.