Study of the Effect of Benthic Community Structure of Taleghan River on the Determination of Water Quality

The healthy condition of the Taleghan River in upstream of the Taleghan dam was studied in order to better understanding the role of benthic invertebrate bio-purification faced to waste water inflows to the river in several parts. Sampling was started from the fall of 2005 and continued to the winter of 2006. In this way, five stations were selected using a pre-sampling strategy based on similarity and dissimilarity coefficients among stations, consisted of 10 sampling points along the river was carried out. The stations 1 and 2 are situated before station 3, where the waste water of Shahrak town enters directly to the river flow. Stations 4 and 5 are located after the entrance of the waste water. Distance between stations remaining constant of 1 Km. All of 13 families belonging to 6 orders were then determined consisted of insect larvae among them Ephemeroptera, Trichoptera and Diptera were dominant and omnipresent. The results showed significant fluctuations of nitrogen compounds from fall to spring passing by winter. Nitrogen pollutant compounds decreased from 1.9 to 1.5 mg.L-1. Chironomids worms as indicators of high trophic current water decreased significantly (P<0.05) from station 3 to 5. Parallel to this reduction of polluted indicators, the healthy state of the river increased in Hilsenhoff Family Biotic Index (FBI). The index was ameliorated from the entrance of Shahrak town waste water from 4.3 to 3.85. Both of these values indicate high qualities but smooth amelioration of the quality. This work consider that the healthy state of the Taleghan river is not in high risks of quality in the moment, but could be easily balanced to poor qualities, if human activities around this basin do not take in account purification plants before rejection to the river.