Restoration of ecosystem functions and efficiency control: case study of the Danube floodplain between Neuburg and Ingolstadt (Bavaria/Germany)

The Danube floodplain is disconnected from its river, and natural water dynamic is inhibited by regulation and hydropower generation. Notwithstanding the hydropower dams, this restoration project aims to bring back natural water dynamics to the floodplain by a new floodplain stream, by ecological flooding and by temporary groundwater drawdown during summer months. Due to the new floodplain stream, former fluctuating water zones which are habitat for the target species Oenanthe aquatica changed to aquatic habitats which are also required. The measure groundwater drawdown aims to enhance the abiotic conditions for this pioneer species of muddy streambanks. The scientific efficiency control compares the situation before restoration implementation with the effects of three different types of groundwater drawdown. For these three types, the hydrological situation was investigated, and the effects on the potential area and on the occurrence of O. aquatica were mapped. The outcome is that one type can enhance germination of O. aquatica, but is detrimental for aquatic organisms. The other type is able to provide the same suitable conditions for O. aquatica, without severely harming the aquatic habitats. The third type cannot reach the needed low water levels and is therefore not a comparable option. The results show that an interdisciplinary monitoring is able to develop a measure suitable for both competing habitat types.