Abstract- The physico-chemical parameters including electrical conductivity (EC), PH, total hardness (TH), chloride, fluoride,dissolve oxygen, turbidity, and sulphate of the water samples of Hirakud dam and Mahanadi River in the command area ofHirakud dam were analysed. The analysed data were then compared with standard value BIS:10500.From the analysed data ofMahanadi river it was found that PH ranges from 6.2-8.3 mg/l indicating slightly alkaline in nature, the turbidity ranges from2.5-4.5 mg/l, total alkalinity is 60-150 mg/l, TH varies from 90-115mg/l, sulphate ranges from 9.5-13.6 mg/l, chloride variesfrom 9.95-22.6 mg/l, fluoride varies in range of 0.22-0.35 mg/l, DO ranges 5.9-7.5 mg/l. On the other hand, water analysed fromHirakud dam, have pH value of 6.6-8.3 mg/l, 75-137 mg/l, TH is 98-120 mg/l, sulphate 12.6-13.8 mg/l, chloride 19.3-24.5 mg/l,fluoride 0.27-0.53 mg/l, DO is 5.7-6.4 mg/l and turbidity 2.4-4.6 mg/l. The assessment of water quality index (WQI) indicatesthat the WQI value for Mahanadi river is 138.8 , whereas that of Hirakud dam is 179.98, Hence, both are belongs to categoryof class-E and unfit for drinking, but, however on comparison Hirakud dam water was found to be more contaminated thanMahanadi river water.Keywords: PH, Conductivity, Total hardness, Dissolved oxygen, Alkalinity, WQI