We organize a scientific workshop devoted to the presentation of current research results on lake ecosystem modeling, in France.

The development and application of deterministic models of lake ecosystem have grown rapidly since the 1990s due to the spread of computer technology and the need to improve the management of lakes and reservoirs.

These models help in the synthesis of knowledge. On the one hand, they can be used to test and improve understanding of lake ecosystem functioning by comparing their results with observations. On the other hand, they can help to forecast future ecosystem responses to different management scenarios or meteorological forcing. These results can support the management of the lakes and their watersheds.

Nevertheless, the predictive capacity of these models is often very low; their results are impaired by considerable uncertainty and the definition of the model structure remains a research issue. A detailed description of the physical and biogeochemical processes often is a source of overparametrization. Compared to simpler models, detailed models have less uncertainty on the functioning of the ecosystem, but their behavior itself becomes unpredictable because of the large number of parameters to fit. Moreover these parameters can be strongly correlated to each other. Thus, the right level of complexity for developing reliable and useful models remains a research challenge.

Therefore, this scientific workshop is devoted to share the main results on lake ecosystem modeling currently performed in France and the links with monitoring and management of these water bodies. Different modeling approaches will be presented and discussed. We will highlight the main achievements and we will try to outline the key research issues for the next years.