The rates and mechanisms through which rivers transport nutrients reflect the health and productivity of an ecosystem. Understanding nitrogen processing and removal is essential in the context of anthropogenic inputs. Nitrate often infiltrates watersheds through fertilizer runoff or decaying organic matter, and excess concentrations can drive eutrophication and algal blooms. Floodplains in gravel bed rivers are highly productive and have high surface water-groundwater exchange, potentially increasing nitrate processing. Here we developed a nitrate budget for the 15-km Nyack floodplain reach of the Middle Fork Flathead River. While most studies focus on small streams, single-station approaches, or tracer-methods, we sought to quantify nitrate dynamics at a larger spatial scale through a two-station, high-frequency monitoring approach. We established primary monitoring sites upstream and downstream of the Nyack along the main channel of the Middle Fork and in a groundwater fed spring stream. Additionally, we sampled four intervening tributaries to account for external nitrate inputs contributing to downstream variation. Nitrate concentrations were measured using submersible ultraviolet nitrate analyzers (SUNAs) deployed for 8d alongside deployed alongside dissolved oxygen loggers, while discharge was quantified through use of an acoustic doppler current profiler. To quantify the budget, we calculated average nitrate mass flux at each site and calculated contribution based on relative location to the floodplain. Results indicated minimal net change in nitrate flux between upstream and downstream sites, with measured downstream flux exceeding expected values by only 7.9% (0.219 mol/s measured vs. 0.203 mol/s expected), suggesting the Nyack floodplain was neither a large net source nor sink of nitrate during our sampling period. No net change does not mean nitrate is unreactive; future research should estimate the gross fluxes in NO3- , specifically as they relate to hyporheic and groundwater interactions within the Nyack.