Point source inputs are a major source of nitrogen (N) in many U.S. and world rivers.  Recent findings indicate that aquatic N processes such as denitrification saturate, so that as nutrient concentrations increase, a streams ability to influence nutrient flux declines.  In contrast, nutrient removal processes become more effective at influencing nutrient fluxes at lower flows due to hydraulic changes.  In addition, when flows decline in point-source dominated systems, dilution is reduced and concentrations tend to increase.  As a result, these three factors – dilution, N saturation, and hydraulics - compete to determine nutrient removal (as a proportion of inputs) and concentrations.  We used a reach-scale model to explore interactions among the three factors under various point source and hydrologic scenarios. Results indicate that with higher point sources, overall removal proportions are reduced due to saturation, whereas peak removal shifts towards higher flows. Concentrations increase monotonically as flows decline.  In contrast, if first order kinetics are assumed, removal remains constant, while concentrations peak at intermediate flows due to interactions between dilution and hydraulic conditions.  Interaction among process kinetics, dilution, and hydraulics can therefore influence whether river systems are able to purify nutrient inputs and influence water quality, especially during drought conditions.