The researchers assessed the water quality of the Tigris River in Baghdad for drinking purposes using a Water Quality Index (WQI) based on 16 different parameters. The study found that the water quality was very poor, with high levels of turbidity, hardness, conductivity, and solids due to human activities along the river. The water was deemed unsuitable for drinking without further treatment. The WQI proved to be a useful tool for managing water quality and identifying pollution sources in surface waters.