Assessment of Water Quality Index for the Study of Water Quality Deterioration of the Tigris River in Baghdad City, Iraq

This study was conducted to evaluate the annual Water Quality Index (WQI) using a set of physical, chemical, and biological water quality parameters. Twenty-three parameters were selected, including temperature (°C), turbidity (NTU), Total Alkalinity (TA) as CaCO₃, Total Hardness (TH) as CaCO₃, calcium (Ca²⁺), chloride (Cl⁻), magnesium (Mg²⁺), pH, conductivity, sulfate (SO₄²⁻), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), iron (Fe²⁺), aluminum (Al³⁺), nitrite (NO₂⁻), nitrate (NO₃⁻), ammonia (NH₃), orthophosphate (PO₄³⁻), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Fecal Coliform (FC), Total Coliform (TC), and Aerobic Plate Count (APC). Twelve stations along the Tigris River were selected for analysis, covering the period from 2009 to 2023. The physical, chemical, and biological parameters were analyzed using the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) method. The study aimed to assess the water quality status of the Tigris River based on WQI. The calculated WQI values ranged from 36 to 54. The results indicated marginal water quality at stations S1 to S4; however, upon entering the city, a significant decline in water quality was observed, with values indicating poor and severely polluted conditions at stations S5 to S12. Some parameters, such as TDS, were within acceptable limits for domestic use (according to EPA standards) at the upstream station (S1), but were found to be unsuitable at the remaining stations. Both E. coli and T. coli were within permissible limits only at station S1 and exceeded standards downstream. These field observations reveal a deterioration in water quality, primarily due to human activities, particularly industrial and domestic discharges. The primary objectives of the research were to analyze the physical, chemical, and biological characteristics of the river water, assess the water quality index, and propose remedial measures to mitigate the ongoing degradation and its potential consequences. Based on the urban WQI results, it can be concluded that if current conditions persist, future years are likely to follow a similar trend to that observed between 2009 and 2023.