The Pampa River, one of Kerala's prominent rivers, plays a vital ecological, cultural, and religious role, serving as the lifeline of the Sabarimala pilgrimage. Every year, during the Mandala–Makaravilakku season, a large influx of pilgrims leads to a significant increase in waste generation, sewage inflow, and ritual-based discharges into the river. In addition to these anthropogenic influences, natural factors such as monsoon floods, pre-monsoon low flows, and seasonal fluctuations further affect the river's water quality. This study undertakes a systematic, seasonal, and event-based assessment of the Pampa River to understand pollution dynamics, identify critical stress periods, and support sustainable river basin management and pilgrimage planning. During the pilgrimage season, the river is extensively used by devotees for bathing and various ritual activities, often resulting in contamination and a decline in water quality. The present work involves water quality evaluation during three phases before, during, and after the pilgrimage season using the Water Quality Index (WQI) method integrated with GIS-based spatial analysis. The study examines physical, chemical, and microbiological parameters, including oxygen demand, nutrient concentrations, and indicators of organic and inorganic pollutants, along with other relevant water quality determinants from September to February month. The results clearly indicate that the river water quality is highly dynamic and is significantly influenced by both natural seasonal variations and anthropogenic activities.