A need of water quality assessment of the rivers before enters into the human induced habitations play a vital role in maintenance of ecological balance. The surface water samples were randomly collected from the Tunga and Bhadra reservoirs situated in the downstream catchments of Western Ghats with semi-evergreen and mixed deciduous forests during January 2018 to December 2019. The samples were analyzed as per the Standard Methods prescribed for drinking water analysis. Increased trend of pH in Pre-monsoon and decreased trend in post monsoon season was observed and the mean concentrations of pH was ranged between 7.30 and 8.02. Electrical Conductivity values were found to be <143µS/cm and indicated that the water is suitable for irrigation and drinking purposes. The Total Dissolved Solids and Total Hardness values were indicated as soft water as values are <75 mg/L.  A significant relation was noticed between Dissolved Oxygen (DO) and Biochemical Oxygen Demand during Post monsoon season.  Whereas, no relationship was existing with water quality parameters in Tunga River and Bhadra reservoirs during monsoon (2019) wherein highest floods were received in this season.  An insignificant pollution load was observed as the water flows through forest areas and no relationship exists between past mining activities in the Bhadra river catchment, sedimentation of reservoir and water quality. However, it is suggested to control of alterations in land use / land cover, use of fertilizer and pesticides, mono culture plantations and developmental activities to maintain the water quality in the study area to meet the domestic demands in the downstream.