Samenvatting

This research examines the water quality of Lake Volkerak-Zoom, focusing on annual returning blue-green algae (Microcystis) blooms. In addition, this research is focused on the possibility to sustainably remove 50% blue-green algae (Microcystis) from Lake Volkerak-Zoom using nutrient related measures, taking into account possible climate change effects until 2050. This research is mostly conducted by desk research.
A system analysis of Lake Volkerak-Zoom with its ecosystem components was conducted from a previous study of Deltares, (2021). This system analysis is used as the basis of this research to visualize what components are most important for the growth of blue-green algae (Microcystis). A further desk research is based on these important ecosystem elements, with as most important element; nutrients and the growth impacts of blue-green algae (Microcystis). These most important elements were placed within a DPSIR approach and further researched. Subsequently, two possible nutrient-related measures could be researched on its possibility and effectiveness. The chosen measures within this research are a 20% reduction of the discharging rivers from Brabant (Dintel and Vliet) on Lake Volkerak-Zoom and a nutrient removal of 60% total-N and 50% total-P in 500 hectares wetlands in Lake Volkerak-Zoom. To include the climate change in the model, an average temperature increase is chosen of 1,8˚C until 2050. Since this measure is included within the model, this can more or less be seen as one of the measures, although, climate change is not nutrient-related.
Most important results from this research were the algae removal percentages the two nutrient related measures resulted. Both measures were similar in its results. Eventually could be concluded that on average, both measures are effective for the removal of 30% blue-green algae (Microcystis) in lake Volkerak-Zoom. In addition, climate change effects were included. This possible change until 2050 gave interesting results in terms an algal removal efficiency of 10% – 20% could be concluded. Although, some interesting removal efficiencies are concluded, these do not meet the requirements stated in the main research question of this research, to remove 50% blue-green algae (Microcystis). To reach this 50% blue-green algae (Microcystis) removal efficiency, a further nutrient reduction will be required.