This study was conducted to assess the water quality of the Diwaniyah river by using the water quality index for irrigation uses (WQII), which was done over the period from November 2019 to June 2020. The water quality of the river shape has a different pattern over various climatic areas. Our study evaluated the spatial scale variation of the water quality index (WQI) to comprehend this phenomenon. They were analysed based on the standard methods for the following parameters: SAR, HCO3–, Cl–, Na+, and EC. The assessment of water quality was made using the water quality index (WQI). The calculated value of WQII for six stations along the river for the eight months duration showed that the water might be utilised in soils texture with moderate to high permeability magnitudes; being proposed that moderate leaching of salts for soils and plants with moderate tolerance to salts may be grown in moderate restrictions (MR) depending on the index of irrigation water quality.