Using Game Theory Algorithm to Identify Critical Watersheds based on Environmental Flow Components and Hydrological Indicators

Abstract 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). Therefore, the present study was conducted to identify critical watersheds using HI and EFC under the influence of the dam and without the impact of the dam using the Borda Scoring Algorithm (BSA) based on Game Theory (GT) in Nir-Chay, Balkhlou-Chay and Qareh-Sou Rivers as consequent stations in northern Iran. Indicators of Hydrological Alteration (IHA) software was used to quantify river flow indices. 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 Game Theory (GT) were used, and the scores were assigned to watersheds based on Borda Scoring Algorithm (BSA). Based on the results, it can be said that in the Doost-Beiglou watershed, the small flood peak in the pre-dam period was 14.08, which was reduced to 3.5 in the post-dam period. The scoring of the studied watersheds based on HI and EFC GT 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, which highlights the importance of these watersheds for managers and decision-makers in making optimal decisions.