Evaluation of water quality in Ghaleh Rudkhan River using macroinvertebrate density and Hilsenhoff Biotic Index

Bio-indicators is a method for assessing water quality. The responses of benthic macroinvertebrates to pollution are more reliable. These organisms vary in their sensitivity to environmental pollution. The objectives of the present study were evaluation of health status and pollution of the Ghale Rudkhan River using macro benthos richness, Hilsenhoff biotic index and Shannon- Wiener diversity index. Five sampling sites were selected. Samples were taken from May to November 2017. A Surber sampler (area 900 cm2, 300μ pore size)was used for sampling with three replicates in each site. Samples were preserved in ethanol 96% and transported to the laboratory. Total of 5134 specimens of macroinvertebrates belonging to 35 genera, 30 families, 10 orders, 4 classes and 3 phyla were identified. Aquatic insect larvae dominated the samples. The highest abundance belonged to Diptera, Ephemeroptera, Trichoptera and Plecoptera in a descending order. The highest and lowest Shannon diversity index (2.28 and 0.42) were observed in May (site 4) and September (site 3) respectively. Based on Hilsenhoff (HFBI) index the water quality at sampling site 1 (upstream), site 3 (before trout fish farm), site 4 (immediately after fish farm) and site 5 (downstream) was “Good” and at sampling sites 2 (in vicinity of the tourist complex) was “Fair”. Based on monthly assessments of these indexes the water quality state in May and October were Excellent and Fair respectively.