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

Abstract

High suspended sediment concentrations in Lake Marken in the Netherlands 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 currently being studied is the construction of sheltered areas in the north-west part of Lake Marken. A strategy is being followed for implementation of these measures that combines in-depth system knowledge with stakeholder aspects. This study discussed what knowledge of the underlying physical and ecological processes was needed and how it was applied, in the strategy. A coupled silt model for Lake Marken was used to study the effects of the structures on hydrodynamics, waves and sediments. The results of the silt model simulations were interpreted with in-depth ecological expert knowledge to assess the ecological impacts of the structures. The effects of the considered sheltered areas on water transparency and wave and silt dynamics are limited, compared to the scale of the lake. These changes nevertheless provide local opportunities for ecology, and its effectiveness may be enhanced by local undeepening.