Integrated hydro-ecological modelling approaches to assess reconnection options of water bodies – A case study of the Lower Lobau | Integrierte gewässerökologische Modellansätze zur Beurteilung von Gewässervernetzungsvarianten am Beispiel der Unteren Lobau

Floodplains and wetlands are among the most endangered ecosystems worldwide. River-regulation and flood protection measures cut off these formerly highly dynamic systems from their natural water level fluctuations and water exchange conditions leading to siltation processes. Restoration measures to counteract these developments need to be assessed for the effect on currently established habitats and communities in order to estimate their effects, as species with different habitat preferences and different protection status do react distinctly different. This article will present how habitat modelling was used in a case study of the Untere Lobau to assess and predict the effects of potential management measures. The Untere Lobau is a wetland ecosystem of the Danube east of Vienna. It is part of the national park Donau-Auen and a protected area according to the EU habitat-directive. Prior to the river regulation, at the end of the 19ᵗʰ century, the Untere Lobau was a dynamic floodplain. Today, siltation processes endanger especially the status of the aquatic habitats. Three management options were investigated: 1) business as usual – No implementation of additional hydrological measures, thus siltation processes are not mitigated; 2) a water enhancement scheme – A small amount of water is supplied to preserve the water bodies at the current status quo; 3) partly reconnection – An upstream reconnection of the floodplain to the main channel of the Danube, leading to a more rheophilic characteristic of the system moving towards conditions prior regulation. Based on a model approach and calculating habitat preferences via binary logistic regressions of selected species from different organism groups, an increase or decrease of available suitable habitat area (weighted usable areas) could be estimated. This study proofed clearly that models can assess the effects of hydrological management measures on the biocenosis and that they are a valuable tool for supporting the decision taking process in wetland management.