“…Ability of dispersion, dilution or depuration in a body of running water is a particular feature, highly variable, hence the difficulty of generalizing study characteristics of these processes. Velz 9 states that the character of water resources is dynamic and complex (emphasizing estuarine regions, with spatial and temporal variations), and the stable equilibrium in the hydrological environment is established through complex interactions between water flow channel and the vegetation cover, which are relatively time-varying (theme also seen in Cunha 13 ). Drainage systems nature is radically influenced by physiography (in a stable watershed, determining factors as climate, precipitation, temperature, wind speed, vapor pressure, solar radiation, are highly variable in time and space), which induces variations in flow and assimilation capacity of waste 9,11,14,15,16 .…”