Using game theory algorithm to identify critical watersheds based on environmental flow components and hydrological indicators

Improper use of water resources has caused significant changes in natural river flow (NRF), which indicates the need to assess changes in hydrological indicators (HI) and environmental flow components (EFC). This study quantitatively assessed 26 hydrological indices (HI) and 21 effective flow components (EFC) at four river gauge stations in Ardabil, Iran, including Nir, Pol-e-Almas, Arbab-Kandi and Doost-Beiglou. It used the Borda scoring algorithm (BSA) based on game theory (GT) to determine watershed vulnerability. With rivers playing a crucial role in ecosystems and human life, the research focused on NRF alterations' impact in Ardabil province. In the research methodology, indicators of hydrological alteration (IHA) software were used to quantify river flow indices. In total, 26 HI and 21 EFC have been quantified and were used to identify critical watersheds. Principal component analysis (PCA) was used to determine the most significant indicators. After the data reduction, the initial matrix and comparative preferences of GT were used, and the scores were assigned to watersheds based on BSA. The analysis identified four significant groups of components within hydrological indices (HI) and effective flow components (EFC) using the main component. The first and second components, with 59.96% and 32.00% variance, were more important than the third and fourth components, which accounted for 4.43% and 2.83% variance. In the Doost-Beiglou watershed, a notable change occurred, where the small flood peak decreased from 14.08 in the pre-dam period to 3.5 in the post-dam period. The scoring of the studied watersheds based on HI and EFC, game theory showed that the watersheds affected by the dam with the scores of 216 and 174 were ranked first and were selected as the most critical watersheds in the study area. As a concluding remark, in the watersheds of Pol-e-Almas and Doost-Beiglou, which were affected by Yamchi and Sabalan dams, significant changes were observed in HI and EFCs. Therefore, in terms of NRF, Balkhlou-Chay and Qareh-Sou Rivers were categorized as critical conditions. In future research, consider incorporating ecological indicators alongside hydrological and environmental ones to better understand river flow dynamics. Additionally, explore the influence of changing climatic parameters on water resources. Engage local stakeholders and implement co-management approaches, using comprehensive data to analyze river flow trends.