Identification Of The Macrobenthic Population In Three Tributaries Of The Kordan River (Senj, Aghasht, And Baraghan) And Water Quality Assessment Of These Rivers Using Biological Indices

Abstract

Given that macrobenthic organisms are highly responsive to environmental changes—including alterations in the physical and chemical parameters of water, as well as the impacts of industrial and agricultural pollution—the study of benthic communities and the assessment of water quality according to biological indicators are widely regarded as one of the most prevalent and cost-effective approaches for monitoring river health. Therefore, utilizing this method with its unique and beneficial characteristics holds a very crucial position in water quality assessment discussions all over the world, including in more water-scarce countries like Iran. This research was conducted to identify the macrobenthic population and evaluate the health of the water in three key tributaries of the Kordan River—Senj, Baraghan, and Aghasht—through monthly sampling using a Surber sampler, with three quantitative replicates and one qualitative sample collected during the spring and summer of 2023. Alongside sampling at each branch, the parameters of PH, electrical conductivity (EC), dissolved oxygen (DO), and temperature were also recorded. The benthic organisms were identified to the genus level, belonging to 7 classes, 15 orders, 55 families, and 113 genera, with aquatic insects being the most diverse and dominant group. Among the three investigated rivers, the Baraghan River exhibited the highest diversity with 26 identified families, while the Senj River had the highest density, with 13,776 collected specimens. To assess the health of the three rivers, the Hilsenhoff, BMWP, ASPT, and EPT indices were calculated. According to the Hilsenhoff index, all three rivers were classified as "Good." The EPT index rated the condition of each branch as "Excellent," while the BMWP index indicated a "Good" status for all rivers. Based on the ASPT index, the Baraghan River was evaluated as "Very Good," while the Senj and Aghasht Rivers were rated as "Good." Although various agricultural, aquaculture, and tourism activities take place along the banks of these rivers, particularly Baraghan and Aghasht, the results indicate that the current self-purification capacity of the three rivers exceeds the impact of environmental pollutants.