As harmful algal blooms begin to appear in unexpected places such as rivers in predominantly forested systems, a better understanding of the nutrient processes within these contributing watersheds is necessary. However, these systems remain understudied. Utilization of high-resolution water quality data applied to deterministic numerical modeling has shown that a 0.42% watershed area backwater riparian wetland along the Ohio River floodplain can attenuate 18.1% of nitrate discharged from local mixed-use watersheds and improves in performance during high loading times due to coinciding increased hydrological connectivity and residence times of water in these wetlands. Loading from the Fourpole Creek watershed was typical for mixed-use systems at 3.3 kgN/ha/yr. The high-resolution data were used to improve boundary condition parameterization, elucidate shortcomings in the model structure, and reduce posterior solution uncertainty. Using high resolution data to explicitly inform the modeling process is infrequently applied in the literature. Use of these data significantly improves the modeling process, parameterization, and reduces uncertainty in a way that would not have been possible with a traditional grab sampling approach.