Reservoirs are vital water sources that contribute significantly to local ecological and environmental balance, particularly in semi-arid regions. An evaluation of the drinking water quality index (WQI) has been conducted using ten water parameters like electrical conductivity (EC), chloride (Cl-), pH, total hardness (TH), total alkalinity (TA), phosphate (PO43-), dissolved oxygen (DO), nitrate (NO3-), total dissolved solids (TDS), and sulfate (SO42-). Weighed Arithmetic Index technique is utilized for examining drinking water quality status and USEPA model was utilized to determine the non-carcinogenic risk for ingestion of nitrate of Bhosga reservoir of Kalaburagi district which was measured at five predefined sites from October 2020 to September 2021. All the parameters of potable water were below the allowable limits based on given standards. The maximum WQI results were reported in monsoon season, with a mean WQI value of 48.14 from all the five selected sites, with the pre & post-monsoon seasons a mean WQI result of 46.08 and 43.68, respectively. Overall, the WQI value signifies that the water was of good quality, making it worthy for domestic use. The outcome of this study reveals that the pH and DO position have a substantial impact on reservoir WQI. Non-carcinogenic risk for nitrate ingestion reveled that, seasonal HQ average results for adults and children are ranging between 0.036 to 0.040 and 0.065 to 0.071, respectively and the HQ results for both adults and children were below 1, indicating neither adults nor children had any negative effect. Principal component analysis and cluster analysis revealed that primary causes of water quality degradation were agricultural runoff and anthropogenic activities. To ensure the security and the quality of water supply to people who live in the surrounding region, simple filter treating of reservoir water prior usage is needed.