The present study is considered the first on this sector of the Tigris River after 2003. It is designed for two aims, the first is to demonstrate the seasonal variations in physicochemical parameters of Tharthar-Tigris Canal and Tigris River; the second is to explain the possible effects of canal on some environmental properties in the Tigris River. Water samples were being collected monthly. Six sampling sites were selected, two on Tharthar Canal and four along the Tigris River, one before the confluence as a control site and the others downstream the confluence with the canal. For a period from January to December 2020, nineteen physicochemical parameters were investigated including air and water temperature, turbidity, electrical conductivity, salinity dissolved oxygen, percent oxygen saturation, biological oxygen demand, pH, total hardness, calcium, magnesium, sulphate, total dissolved solids, total suspended solids, total alkalinity, bicarbonate, nitrate and phosphate. The results showed that air and water temperatures were close in both Tigris and canal. The waters were well aerated, slightly alkaline and over saturation was recorded several times, while biological oxygen demand values did not exceed 5 mg/L along study period. The high values of conductivity, salinity, total dissolved solids, total hardness, calcium and sulphate ions in Tharthar water increased in the Tigris River below the confluence. Whereas, the low values of turbidity, TSS, total alkalinity and bicarbonate in the arm diluted in the main river. It has been concluded that Tharthar Canal affected the Tigris River by either increasing or diluting of the Tigris chemical components.

The benthic fauna of the river Euphrates upstream and downstream sectors of Al-Qadisia dam, mid Iraq, was studied for a period of two years (1993 and 1994). Five sampling stations were selected. One station was located upstream the dam, while the other four stations were downstream. A total of 65 taxa were identified. It was clear that the station located immediately downstream (station 2) showed the highest total mean annual density (individuals/m 2 ) represented by higher number of taxa. The benthic community was dominated by oligochaetes especially of families Naididae and Tubificidae as well as chironomid larvae of which the genus Polypedilum was the most dominant one. Seasonal fluctuation of the community showed that the peak of the total number of individuals had appeared during autumn and winter months. Community index of similarity (ISE) was computed for faunal comparison between station 1 and the other stations.

This study was conducted to evaluate the effects of Tharthar Arm on the composition and diversity of Rotifera in Tigris River. Six sampling sites were selected, two on Tharthar Arm and four along the Tigris River, one before the confluence as a control site and the others downstream of the confluence. Seventy-seven species of Rotifera were identified in Tigris, whereas, 60 in the arm. The results showed that low density of Rotifera in Tharthr Arm decreased the density in Tigris from 239812.4 upstream of the confluence to 223315.5 at immediate downstream of the confluence. It also declined the mean values of richness, evenness and Shannon diversity indices from 5.19, 0.69 and 2.14 bit/Ind., before the confluence to 3.97, 0.73 and 2.00 bit/Ind. below the confluence, respectively. Moreover, the highest similarity value was between sites 1 and 6 reached 83.27%, while the lowest value was between sites 1 and 2 recorded as 60.52%. For constancy index, the highest value was 14 in site 1 and the lowest was 8 in site 2.

This study is considered to be the first on this sector of Tigris River after 2003, to evaluate the effect of Tharthar Arm on the composition and diversity of Copepoda in Tigris River. Six sampling sites were selected; two on the Tharthar Arm and four sites along the Tigris River, one before the confluence as a control site and the others downstream the confluence; thirty-five copepod taxa were recorded, 34 taxa in the Tigris River and 25 taxa in the Tharthar Arm. The highest density of Copepoda was 265584.2 Ind./m3 in the site 2 at Tharthar Arm lead to an increasing in Copepoda density in the Tigris River from 63878.2 Ind./m3 in site 1 before the confluence to 127198.3 Ind./m3 in site 4 immediately downstream the confluence. Also, the mean values of richness index and diversity index increased from 1.71 and 0.98 bit/Ind. in site 1 before the confluence to 2.08 and 1.00 bit/Ind. in site 4 below the confluence, respectively. Moreover, the highest similarity percentage was between sites 3 and 4 reached 87.83% while, the lowest percentage was between the sites 1 and 2 recorded 65.41%. For constancy index the highest value was 9 at the site 6 whereas the lowest value was 2 at site3.

This study was carried out to determine the effects of crude terpenoid compound extracts of Melia azedarach L. leaves and fruits on some biological aspects of whitefly Bemisia tabaci (Genn.) under laboratory conditions of 25 ± 2°C and relative humidity of 65-70%. The results indicated a significant effect on eggs and immature stages when treated with 0.5, 1, 1.5, and 2 mg/ml of leaves and fruits. The mortality rate increased with concentration. It reached 98.68, 100, 100, 95.70, 86.30, and 42.68% for eggs, 1st, 2nd, and 3rd nymphal instars, pupa, and adults, respectively, at a concentration of 2 mg/ml for leaves extract. At the same time, it reached 94.86, 100,100, 100, 87.89, and 44.90% for eggs, 1st, 2nd, and 3rd nymphal instars, pupa, and adults, respectively, at a concentration of 2 mg/ml for fruit extract. Also, the proportion of adults who emerged from sprayed eggs reduced to 91.53% and 95.72% when treated with 2 mg/ml of leaves and fruit extracts, respectively. While the developmental period increased to 23.50 and 24.00 days at 2 mg/ml when treated with terpenoid extracts of the leaves and fruits, respectively, compared with 21.00 and 20.83 days at control.