Abstract
Water quality index (WQI) can express water quality status in one term. In addition, conducting of frequent WQI evaluation may give community the required knowledge about the surface water condition. For this reason, this study evaluated the quality of surface water using National Sanitation Foundation Water Quality Index (NSFWQI) and the Oregon water quality index (OWQI). Data collected from three stations located along the Tigris River in Baghdad, during dry and wet season in 2024 and 9 water quality parameters were examined which are dissolved oxygen, potential of hydrogen, dissolved solids, biochemical oxygen demand, turbidity, temperature, phosphate, nitrate and coliforms. Results show that the water quality at the first sampling site (north of Baghdad) and the second sampling site (Baghdad) was fair in both the dry and wet seasons, while the third site (south of Baghdad) had bad water quality according to the NSFWQI in both seasons, while the application of the OWQI shows the river status is very poor in all stations in both dry and wet seasons. The water quality index in wet season were (54.07,50.61, 42.25) for sites 1,2, and 3 respectively while the quality index in dry season was (55.15,55.32,44.02) for sites 1,2 and 3 respectively using the NSFWQI. For the OWQI, the results in wet season were (26.4, 25.7 and 18.2) for sites 1,2, and 3 respectively while in dry season the water quality index was (25.2, 24.07 and 15.2) for sites 1,2 and 3 respectively. The water quality decreased significantly while moving downstream the river. Industrial processes, farming and inhabitants are the major reasons of Tigris pollutants, so the management programs for protecting this essential water source is needed.