The study explains water quality of river Ghaghra, Bihar. Seasonal changes in the water quality of the river observed during Monsoon, several water quality parameters showed considerable changes due to increased run- off water from the catchment and other seasonal factors. A few parameters responsible for temporal variation in water quality of the river Ghaghra was rendered by the parameters like water temperature, pH, turbidity, electrical conductivity, sulphate, phosphate, free CO2, total iron, total alkalinity, total hardness, nitrogen-nitrite, nitrogen-nitrate, carbonate, bi-carbonate, total dissolved solids, total suspended solids, calcium, magnesium, sodium, potassium, chloride, Dissolved oxygen (DO), Biological oxygen demand (BOD) and Chemical oxygen demand (COD). The seasonal changes in water quality of the river were due to seasonal effects and catchment characteristics