Application of the Water Quality Index Model for Groundwater Quality Assessment in the Dibdiba Aquifer, South of Iraq

This study evaluates the Groundwater Quality Index of the Dibdiba Aquifer in the Zubair-Safwan area of southern Iraq. A total of 264 groundwater samples were analyzed over 24 years (2000-2024), divided into three temporal intervals (2000-2007, 2008-2015, and 2016-2024), to assess spatial and temporal variations in water quality. Eleven physicochemical parameters were measured, including pH, Total Dissolved Solids, Electrical Conductivity, major cations (calcium Ca²⁺, magnesium Mg²⁺, sodium Na⁺, potassium K⁺), and anions (chloride Cl⁻, sulfate SO₄²⁻, bicarbonate HCO₃⁻, and nitrate NO₃⁻), using standard analytical techniques (ICP-MS, UV-visible spectrophotometry, and ion chromatography). The results reveal a progressive decline in groundwater quality over time. A 10% reduction in Groundwater Quality Index values was observed between the first and second periods, while the third period showed a marked deterioration, with many samples exceeding Groundwater Quality Index values of 300. Spatially, the southwestern zone showed the best groundwater quality (Groundwater Quality Index: 17-104), indicating good to excellent suitability. In contrast, the northeastern, central, and eastern areas ranged from poor to very poor quality (Groundwater Quality Index: 104-300), with some spots exceeding 300, making the water unsuitable for drinking by WHO standards. The increase in Groundwater Quality Index values is primarily attributed to elevated concentrations of SO₄²⁻, Cl⁻, Mg²⁺, Na⁺, and TDS. These findings emphasize the urgent need for groundwater treatment and integrated management strategies to ensure sustainable water use in the region.