The rate of water resource self-depuration is limited, mainly due to the associated pollutant load. To minimize inherent quality problems, many countries, including Brazil, have adopted Regulatory Decisions targeted at water resource quality. Thus, in this context, this study presents a dynamic model developed to analyze the interrelationships between the flow rate and the concentration of pollutants in the watershed of the Rio das Mortes, Minas Gerais State, Brazil. The methodology was based on the STELLA, a software that allows system dynamic analysis. Official data from the 2000-2009 period, related to the hydrological behavior of monthly average flow rates and pollutant concentrations of Total Manganese and Total Phosphorus allowed simulating and effectuating a sensitivity analysis of the possible effects of changes in pollutant concentrations, in that watershed. The model developed in this study allowed a better understanding of the behavior of the watershed with respect to temporal and spatial pollution changes.