The water quality index was used for the evaluation of the quality of water, as well its impacts on the rotifer abundance, in the Tigris River as it passes through Mishahda City, northern Baghdad. Five sites were selected and samples were collected during October 2019 to September 2020. It was noticed that the index values in most sites have exceeded the upper limits of river waters. The values ranged from 40 (Poor) to 45 (Marginal) in all sites. While, the values were from 42 (Poor) to 65 (Fair) during different seasons. As for drinking usages, the results demonstrated poor or undrinkable (31-40) water in all sites. Meanwhile, the values ranged from 39 (Poor) to 56 (Clear) in regard to seasons. The index values recorded for the purpose of Conservation of Aquatic Organisms ranged from 36 (Poor) to 66 (Fair) in the all sites, and 56 (Clear) to 69 (Fair) during different seasons. Twenty five rotifer species were recorded, including 11, 2, 1, 5, 2, 1, 2, and 1 species of Brachionidae, Euchlanidae, Gastropodidae, Lecanidae, Lapadellidae, Notomanatidae, Synchoetidae, and Trichotoidae, respectively. It is concluded that the water of the Tigris on Mishahda City is considered to be highly contaminated and not suitable for human consumption without the necessary treatment. It was also noticed that the population density of the rotifers community was affected by the river water quality. However, despite the presence of environmental pressures, the rotifers continued to reproduce and conserve.

This study was the first of its kind on the Dejiala River, which is considered one of the main branches of the Tigris River in Wasit Province. Therefore, the study aimed to investigate of some physical and chemical properties of water in the Dejiala River. Monthly sampling stations were conducted for 12 months, which was starting from January to December 2016, during those five stations was chosen which divided along about 58 Km of river; each station was located at a distance of ±10 Km. The results of the study showed a clear correlation between air and water temperature in all stations. Turbidity was recorded a value ranging from 2.36-116 NTU. It was found that the water of the Dejiala was Oligohaline, weak alkaline and well ventilated due high concentrations of dissolved oxygen. The Dejialah River considered as questionable clean water according to BOD 5 value. While the total alkalinity values were recorded from 30.5-427 mg/L, so these values were higher than the normal permissible limits for the Iraqi and international water standards, which is 20-200 mg /L CaCO 3 . It was also found that the water of the Dejiala River was very hard, as well as the it was within the permissible limits of natural water ISSN: 0067-2904Abed and Nashaat Iraqi Journal of Science, 2018, Vol. 59, No.2C, pp: 1026