Due to various natural and anthropogenic activities, quality of water was deteriorated in most towns of the country. These changes make or forced the community to depend on unsafe and poor water consumption. The present study was conducted to assess the physicochemical parameters and calculate water quality index (WQI) of Shaya River found in Robe Town and determine its suitability for Drinking and irrigation purposes. Water samples were collected at four sampling sites and analyzed for various physicochemical parameters. The result obtained that the average temperature was 21.8c0, pH was 7.7, electrical conductivity was 1636 μS/cm-1, turbidity was 57.7 NTU, dissolved oxygen was 5.3mg/l, biological oxygen demand was 3.2mg/l, chemical oxygen demand was 22.4mg/l, total solid was 1554mg/l, total suspend solid was 458mg/l, total dissolved solid was 1096 mg/l, total alkalinty was 239mg/l, total hardness was 635mg/l, calsium was 213mg/l, magnisium was 104mg/l, chloride was 99mg/l, sulphate was 690.5 mg/l, nitrate was 36 mg/l nirite was 0.15 mg/l, total nitrogen was 80 mg/l, ammonium was 0.27 mg/l, phosphate was 0.35 mg/l and total phosphures was 0.37 mg/l of the river water sample. The study indicated that the Average value of parameters such as :- temperature, pH, dissolved oxygen, biological oxygen demand, total suspended Solid, chloride, nitrate, nitrite of the river water samples were within the permissible limit of WHO for drinking purposes. The findings also showed the value of parameters, except Sulphate ion concentration, were within the permissible limit of FAO for irrigation water. Therefore the study indicated that the suitability of shaya river for drinking and irrigation purpose. The river water was found to be unfit for human consumption and was found to be safe and utilizable for irrigation purposes. So water quality management is urgently required to achieve the water quality standards determined by WHO. Correlation coefficient showed highly significant positive and negative relationship. If the quality management was properly maintained, the Shaya River water could be utilized for a wide range of applications such as drinking.