Investigation of water quality changes (temperature & dissolved oxygen) and macroinvertebrates population of Shahrestanak River (Karaj, Iran)

Understanding the quality & biological conditions of aquatic ecosystem is essential for management. In this study, some indices (Temperature & Dissolved Oxygen) of Shahrestanak River (Karaj, Iran) were measured and Hillsenhoff Index (HFBI) was used. This research was carried out from January 2006 for duration of one year in 3 stations of the river with 3 replication for temperature and dissolved oxygen sampling and at the same time different types of macroinvertebrates of the river was sampled. Dissolved oxygen in the River was varied from maximum 13.3mg/l in November to 6.8mg/l in July. The average was 8.3mg/l in this time. The maximum temperature was 12°C in July and minimum was 4.3°C in December. The total average was 7.7°C. In this study, 21 families of macroinvertebrates were identified. Due to seasonal variation, maximum & minimum number of macroinvertebrate sample in winter was belonging to Baetidae and Tabannidae families, respectively. In spring Chironomidae and Stratiomyidae; in summer Chironomidae & Gammaridae families and in autumn Chironomidae and Tabannidae families respectively had maximum & minimum number of macroinvertebrates. The maximum number of abundance was 1575samples/m² which belonged to Chironomidae and the minimum number was 1samples/m² which belonged to Stratiomyidae. The value of Hillsenhoff Index in sampling period was 3.39 to 5.1 and the average was 4.56 which according to the table of Hillsenhoff Index is a cue to the good quality of water during the year of sampling.