ABSTRACT
Eutrophication models emerged in the early 1970s, as a result of our interest for eutrophication in environmental management. They represented a step forward toward incorporating more ecology in the models, but also the river models included more and more ecological components and processes, which were known to affect the oxygen balance for a stream. The simulation of the yearly dynamic of a two trophic level aquatic ecosystem under continuous flow of nutrients, dispersed by turbulent diffusion through the open boundaries, is achieved by using a very small grid size. As pointed out in the introduction, the goals of the models and the characteristics of the model ecosystem in relation to the focal problem determine the components of the models. The model Magic is developed to simulate the effects of acidic deposition on soils and surface waters, operating at the catchment scale and using seasonal or annual time steps.
