Ecological aspects of the restoration strategy for a river-floodplain system on the Danube River in Austria

The key factors determining the ecology of large rivers and their adjacent floodplains are extent, duration and dynamics of the hydrological connectivity between the two compartments, both via surface how and groundwater how. This hydrological connectivity has been strongly reduced in all large European rivers due to regulation and damming. The present paper discusses the scientific background in planning a restoration strategy for the free-flowing stretch of the Danube in Austria. As a first step in this conservation strategy which is within the framework of the 'Alluvium Zone National Park', a large-scale pilot project has been developed to restore the hydrological and ecological integrity of the river-floodplain system. In order to assess the progress towards the project's ecological objectives, various limnological variables (functional descriptors) are to be monitored.