The physico-chemical characteristics of Jayakwadi dam water has been studied during Jan 1989 to Dec 2010. Seasonal variations in water quality parameters in rainy, winter and summer seasons are observed. The result revealed that there were significant seasonal variations in some physico-chemical parameters and “WQI”. An attempt has been made to develop water quality index (WQI), using water quality parameters such as Turbidity, pH, Chlorides, Free saline ammonia as N, Albuminoid Ammonia as N, Dissolved oxygen, Nitrate, Total hardness , Total dissolved solids, Fixed Solids, Iron (Fe), Fluoride (F), Total alkalinity as CaCO3 etc of raw water from Jayakwadi dam through M.S.Pipe line to Farola water treatment plant and filtered water are measured by Regional public health laboratory Aurangabad, Water Quality Index is a dimensionless number with values ranking 0 to 100 A lower index values represent good water & higher index value indicates poor water. This numerical index can be used as management tool in water quality assessment. The water quality index results indicate poor status of raw water during rainy and winter season.