<p>Assessing groundwater quality in suburban zones with poor sanitation systems is an essential step in allocating water resources for suitable purposes. This study aims to assess the processes controlling the water quality and its suitability for human consumption and irrigation using a comprehensive approach that combines statistical analyses and GIS-based WQI. Ninety-four groundwater samples from the Quaternary sand aquifer of Thiaroye were collected during the pre-monsoon and post-monsoon seasons in 2020. These samples were subsequently analyzed to determine chemical parameters such as pH, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^–, SO₄^2-, HCO₃^–, and NO₃^–. To evaluate the quality, the values of chemical parameters were compared to the water quality standards set by the World Health Organization (WHO). PCA and correlation matrix reveal that water mineralization is characteristic of anthropogenic impacts and biogeochemical processes. Seasonal changes in water type and significant seasonal variations of pH values suggest an influence of hydraulic fluctuations in the water quality. Irrigation indices suggest that the groundwater is globally unsuitable for long-term irrigation. The water quality index reveals that most of the water is classified as poor to very poor quality, with a small percentage deemed acceptable or unsuitable for human consumption during both seasons. Hence, the study site is at an alarming stage of groundwater quality deterioration, posing a potential public health risk.</p>