Wüest, Alfred JohnyChappuis, Christel Marie2017-10-162017-10-162017https://infoscience.epfl.ch/handle/20.500.14299/141451In an environment subject to anthropogenic pressures, the understanding of lakes is crucial as they are essential for ecosystems and represent a source of the scarce accessible freshwater existing on Earth. Water quality management is especially designed to protect this precious resource and relies on monitoring programs and model simulations. Case study of this project, Greifensee is a small eutrophic lake located in the northern plateau of Switzerland (ZH). For decades, it has been subject to nutrient-­‐rich runoff from agricultural activities in its catchments, consequence of the fast population growth in the area. These considerable human-­‐related pressures have led to a strong process of eutrophication and significantly altered its water quality. In recent years, although nutrient inputs have been reduced, the lake has still not fully recovered and remains classified as eutrophic. This project developed a 3D coupled hydrodynamic-­‐biological model for Greifensee using the software Delft-­‐3D from Deltares in the Netherlands. Delft-­‐3D has been widely applied in various situations and validated, which makes it an excellent tool for such project. Moreover, the development of the model also relies on two monitoring campaigns, from the Eawag institute and Zürich Kanton. Finally, while the model provides an almost full spatio-­‐temporal representation of the processes happening in this lake, final results simulated fairly well the general trends of chlorophyll-­‐a, dissolved oxygen, orthophosphate and ammonium in terms of mass content and depth distribution. Understanding the ecological dynamics of a eutrophic lake using such kind of simulation will hopefully contribute, on a longer-­‐term perspective, to the better management of the lake towards the recovery of its former ecological status.Inland watersWater qualityOxygenstudent work::master thesis