Rising chloride concentrations in the Great Lakes Basin (GLB), driven largely by road salt application, are exacerbating concerns for freshwater quality and ecosystem health. Although surface runoff has received substantial attention, groundwater is increasingly recognized as a critical long-term delivery pathway for chloride to receiving water bodies. However, transferable methods to quantify groundwater-derived chloride fluxes at watershed scales remain limited. This study presents a multi-scale framework to estimate groundwater contributions to stream chloride loads using continuous monitoring, baseflow separation, and landscape-based scaling. The proposed framework is evaluated using the Credit River watershed (southern Ontario, Canada), which discharges to western Lake Ontario. Continuous discharge and chloride data (2022 – 2024) from four reaches of varying land uses are integrated with digital baseflow separation and criteria to identify groundwater-dominated conditions year-round. Site-specific baseflow chloride fluxes are estimated, normalized to unit-area fluxes, and scaled to the watershed using land use and surficial geology information. Sensitivity analyses assess uncertainty in baseflow parameters and landscape weighting. Preliminary results suggest that baseflow is a major pathway for chloride transport, contributing substantially at upstream and mid-watershed sites and remaining important in the highly urbanized lower reach. Baseflow chloride concentrations and fluxes generally increase downstream and exhibit pronounced seasonal contrasts. Comparisons with nearby groundwater data suggest stream baseflow chemistry reflects integrated, attenuated groundwater signals. Overall, this work demonstrates the potential for a transferable framework to estimate groundwater-derived chloride loading and highlights the need to explicitly account for subsurface pathways in chloride management strategies within the GLB.