A hydroinformatic tool for estuarine water quality management

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Nutrient enrichment is a key factor for habitat degradation due to strong stimulation of opportunistic macroalgae growth, with the consequent occurrence of algal blooms. Residence time is broadly recognised as a key parameter to assess estuarine eutrophication vulnerability and it is related to the eutrophication gradients observed in estuarine systems. In the last two decades, the southern arm of the Portuguese river Mondego estuary was stressed by an eutrophication process due to massive nutrient loading from urbanised areas, intensively agricultural land runoff and sensitive changes on estuarine hydrodynamics induced by the silting up in its upstream area. The aims of this work were the development of a hydroinformatic tool − the MONDEST model − coupling hydrodynamics, water quality and TempResid modules, and its application to calculate residence time values, at different simulated hydrodynamic scenarios and nutrients loading characteristics. The results obtained for this estuary allow us to assess the influence of freshwater inflows and nutrient discharge characteristics on residence time spatial distribution. This work shows that the MONDEST model constitutes a powerful tool for enhancing systems eutrophication vulnerability assessment in order to establish the best water quality management practices for the environmental sustainability of this complex ecosystem.