Practical measures for improving the ecological state of lake Marken using in depth system knowledge

For Lake Marken in the Netherlands, high suspended sediment concentrations result in reduced ecological values and prevent goals and standards from being met (Water Framework Directive, Natura 2000). A practical measure to improve the ecology that is currently studied is the construction of sheltered areas in the North West part of Lake Marken. For implementation of this measure, a strategy is being followed that combines in depth system knowledge with stakeholder aspects. In the present paper we will show which knowledge of the underlying physical and ecological processes was needed and how it was applied in the strategy. We used a coupled silt model for Lake Marken to study effects of the structures on hydrodynamics, waves, and sediment. Results of the silt model simulations were interpreted with in depth ecological expert knowledge to assess the ecological impact of the structures. Effects of the considered sheltered areas on transparency and wave- and siltdynamics are limited compared to the scale of the lake. However, these changes give local opportunities for ecology. Its effectiveness may be enhanced by local un-deepening.