Monitoring and assessment of water quality in the Haraz River of Iran, using benthic macroinvertebrates indices

The objective of this study was to assess the relationship between river water quality and the distribution of benthic macroinvertebrate communities in the Haraz River in Iran. Using a surber net sampler, benthic macroinvertebrate communities along the stream was sampled in wet and dry seasons of 2015 at nine stations with three replications. The physicochemical water quality parameters were measured in the field by water checker. Hilsenhoff biotic Indices, Shannon Wiener Diversity Indices, Average Score per Taxon (ASPT) Index and Pielou Evenness Index were applied to carry out a biological assessment of water quality. A total of 3781 (spring 769, summer 1092, autumn 1095 and winter 825) benthic macroinvertebrate specimens belonging to 4 orders, 11 classes and 16 families were identified. The lowest number of taxa was recorded in spring while the highest was recorded in autumn. Station 9 had the lowest number of taxa while the highest number of taxa was recorded at station 3. The average values (±SD) of the water quality parameters were temperature 14.75 ± 4.38 °C, pH 7.93 ± 0.62, water flow 14.11 ± 9.04 m3 s−1, electric conductivity 532.75 ± 161.35 μmohs cm−1, total dissolved solids 296.61 ± 76.21 mg L−1, salinity 0.28 ± 0.07 mg L−1, turbidity 580.77 ± 149.92 NTU and dissolved oxygen 8.08 ± 0.75 mg L−1. The assessment of stations 1 to 6 indicated that water quality conditions were suitable. In addition, substantial level of organic pollution was observed in stations 7 and 8. In station 9 water quality was fairly poor, requiring a more favourable management based on the capacity of the self-purification of the Haraz River.