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Largely through conservation and management activities, extensive effort has been made in the Great Lakes region to protect and improve water quality, yet tracking progress in streams and rivers remains a challenge. Phosphorus loading to the Great Lakes is of primary interest due to associations with eutrophication and harmful algal blooms. Using continuous flow records and monthly discrete water samples, fluxes of total phosphorus (TP) and dissolved orthophosphate (DP) for 24 U.S. Great Lakes tributaries for the period of 2011 to 2020 for using Weighted Regressions on Time, Discharge, and Season (WRTDS) with Kalman filtering. Changes in fluxes over this period were estimated using flow-normalization with bootstrapped confidence intervals. Results indicate that flow-normalized TP fluxes likely (posterior mean probability > 0.9) decreased at 16 of 24 sites and increased at one site. In contrast, fluxes of DP likely decreased at 8 sites and increased at 1 site. These results indicate that tributary loading of phosphorus to the Great Lakes has likely decreased in the last decade after normalizing for variation in discharge. However, greater discharge toward the end of the decade in 20 of the 24 tributaries has offset much of those estimated water quality improvements as actual TP and DP loads decreased in only 9 and 6 sites, respectively. This study demonstrates an approach for describing changes in water quality across the Great Lakes Basin, which highlights the ongoing need for long-term monitoring to assess whether management actions are having beneficial effects. [ABSTRACT FROM AUTHOR]