Lake Winnipeg is highly impacted by excess nutrient loads exacerbating eutrophication. Past research has partially attributed these loads to the increasing intensity and extent of agricultural activity in the watershed. Despite the widely known issues facing Lake Winnipeg, accurate predictions of nutrient loading, and understanding of how varying combinations of land management, land use and hydrological management influence these loads, remains to be seen. This study focuses on key catchments in the Lake Winnipeg Basin which exemplify long-term hydrological and land management changes in the basin between the years 2000-2020. We use Weighted Regressions on Time, Discharge and Season (WRTDS) to estimate the riverine fluxes of phosphorus (P) and nitrogen (N) based on daily average flow and periodic water chemistry data. Further, we examine concentration-discharge (C-Q) relationships for N and P over a range of time scales (seasonal, annual, multi-year) to determine patterns of hysteresis, dilution, and enrichment, from which we draw inferences about nutrient sources and transport pathways. Subsequently, we compare identified trends in loads and C-Q relationships with land use and hydrological management records in the catchments to assess their impact on the transport and storage of nutrients.