Routine assessment of the physicochemical properties of dam reservoir water is a crucial component of dam management strategies for preventing issues related to the water quality and corrosion of the dam's structural components. The significance of Kainji Dam as the largest hydro-power plant in Nigeria is crucial. An independent assessment of the average values of the basic physicochemical properties of the dam reservoir water is presented in this paper. Water samples were collected weekly from the reservoir over a period of 52 weeks from 1st November, 2024 to 31 October, 2025, with each sampling session completed within 30 minutes. The samples were collected in 250-mL polyethylene bottles at 80 random locations in the free-flowing water areas of Kainji Lake, within a band of about 1000-1500 meters upstream away from the dam. Experienced fishermen, using their own canoes assisted in the task. Each weekly collection of water samples was combined to create a representative sample for that week. Certain physicochemical properties, including temperature, pH, total dissolved solids (TDS), dissolved oxygen (DO), and electrical conductivity (EC) of the representative sample were measured immediately on-site after preparing each sample. Other properties were measured in the laboratory using standard methods and properly calibrated equipment. The average value of each physicochemical property was then found by summing its respective values for 52 different weeks and dividing by 52. Analysis of the results indicates that all the average values of the properties fall within accepted range values for water quality, according to the Nigerian Standard for Drinking Water Quality (NSDWQ) and the World Health Organization (WHO), indicating negligible pollution; suitability of the water for drinking, a healthy aquatic ecosystem, and other uses. The water can however, corrode the material components of the dam due to its physicochemical properties being significantly different from non-corrosive standards.