The Winkler Aquifer is an important resource for municipal water supplies in south-central Manitoba. Groundwater quality within the aquifer is vertically stratified, with freshwater overlying brackish groundwater. The elevation of the 250 mg/L isochlor has been used historically to define the fresh-brackish interface and to determine the distribution of freshwater available for water supply purposes. When compared with previous surveys, the isochlor monitoring data is useful to evaluate the aquifer response to pumping and to inform aquifer management decisions and strategies. Electrical Conductivity (EC) is a commonly used proxy for chloride (Cl) concentrations in groundwater. The Cl-EC ratio for the Winkler Aquifer was calibrated using an extensive geochemistry database maintained by the City of Winkler. The 250 mg/L isochlor corresponded with an EC value of 1,925 uS/cm. The analysis indicated a strong correlation, with approximately 96% of the variation in chloride captured in the distribution of EC values. The EC profile was surveyed in numerous wells across the Winkler Aquifer. The resulting isochlor profile was similar to previous results in the northern portion of the aquifer; however, the freshwater interface appeared to be up to 12 meters deeper where newer brackish pumping wells were in operation. Overall, the results suggest that the increased rates of brackish groundwater extraction, along with the promotion of freshwater recharge to the aquifer, have had an observable influence on the distribution of groundwater quality within the Winkler Aquifer. Additional surveys to capture seasonality effects and pumping dynamics will improve the analysis and interpretations.