Ganesh chaturthi is one of the main festivals celebrated in India, it is the most celebrated in western India. After predetermined time idol is immersed in water bodies every year. As the extent of idol immersion increases with increasing population with limited water bodies hence water pollution increases, which is alarming situation. In present study total five sampling stations were identified during current year (2009) with respect to idol immersion sites from different cities of South Gujarat i.e. Surat, Navsari, Valsad, Autl-Pardi and Vapi. All the samples collected by means of composite sampling to know the physico-chemical quality of all river water. The analysis was carried out for pH, temperature, color, DO, COD, chloride, hardness, SS, TDS, conductivity, and phosphate parameters. The results obtained reveals that almost all river water becomes acidic after idol immersion except Par river. Parameters like hardness, chloride, color, SS, TDS increases after idol immersion in all rivers except Par river for TDS. DO is decreasing drastically after the next day of idol immersion at all the rivers which is indication of pollution. The trend of increasing such parameters indicates that idol immersion affect the water quality to the extent with respect to self purification of water and flow of stream of the river.