Gabriele Weigelhofer

Current status and restoration options for floodplains along the Danube River.

Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem services. In most of the large river systems worldwide, a tremendous reduction of floodplain area has occurred in the last 100 years and this loss continues due to pressures such as land use change, river regulation, and dam construction. In the Danube River Basin, the extent of floodplains has been reduced by 68% compared to their pre-regulation area, with the highest losses occurring in the Upper Danube and the lowest in the Danube Delta. In this paper, we illustrate the restoration potential of floodplains along the Danube and its major tributaries. Via two case studies in the Upper and Lower Danube, we demonstrate the effects of restoration measures on the river ecosystem, addressing different drivers, pressures, and opportunities in these regions. The potential area for floodplain restoration based on land use and hydromorphological characteristics amounts to 8102 km(2) for the whole Danube River, of which estimated 75% have a high restoration potential. A comparison of floodplain status and options for restoration in the Upper and Lower Danube shows clear differences in drivers and pressures, but certain common options apply in both sections if the local context of stakeholders and societal needs are considered. New approaches to flood protection using natural water retention measures offer increased opportunities for floodplain restoration, but conflicting societal needs and legal frameworks may restrict implementation. Emerging issues such as climate change and invasive non-native species will need careful consideration in future restoration planning to minimize unintended effects and to increase the resilience of floodplains to these and other pressures.

Effects of riparian forest buffers on in-stream nutrient retention in agricultural catchments.

In northeastern Austria, marshlands have been turned into the most productive arable land of the country. As a result, most headwater streams show structurally degraded channels, lacking riparian buffer zones, which are heavily loaded with nutrients from the surrounding crop fields. The present study examines whether longitudinally restricted riparian forest buffers can enhance the in-stream nutrient retention in nutrient-enriched headwater streams. We estimated nutrient uptake from pairwise, short-term addition experiments with NH, NH, PO, and NaCl within reaches with riparian forest buffers (RFB) and degraded reaches (DEG) of the same streams. Riparian forest buffers originated from the conservation of the pristine vegetation or from restoration measures. Hydrologic retention was calculated with the model OTIS-P on the basis of conductivity break-through curves from the salt injections. A significant increase in surface transient storage was revealed in pristine and restored RFB reaches compared with DEG reaches due to the longitudinal step-pool pattern and the frequent occurrence of woody debris on the channel bed. Ammonium uptake lengths were significantly shorter in RFB reaches than in DEG reaches, resulting from the higher hydrologic retention. Uptake velocities did not differ significantly between RFB and DEG reaches, indicating that riparian forest buffers did not affect the biochemical nutrient demand. Uptake of NH was mainly driven by autotrophs. Net PO uptake was not affected by riparian forest buffers. The study shows that the physical and biogeochemical effects of riparian forest buffers on the in-stream nutrient retention are limited in the case of highly eutrophic streams.

Optimised management strategies for the Biosphere reserve Lobau, Austria - based on a multi criteria decision support system

Abstract Without sustainable rehabilitation measures, the Lobau, a freshwater Biosphere Reserve, will soon became a primarily terrestrial ecosystem with major implications for its rich aquatic and amphibic biodiversity. An innovative ecosystem management scheme for this Danube floodplain needs to optimally balance between conservation and restoration objectives and to harmonize the partly competing ecologic and socio-economic requirements for the next 40 years. Therefore, we present a project dealing with the development of a multi-criteria Decision Support System (DSS), based on interdisciplinary historical analyses and state-of-the-art ecosystem modelling. The DSS will assists multiple stakeholders in finding coherent and realistic management alternatives, by linking all objectives and measures in a transparent and reproducible way.

Effect of enhanced water exchange on ecosystem functions in backwaters of an urban floodplain

This study evaluated the effects of a controlled surface water connectivity scheme on several backwaters in an urban floodplain within the city limits of Vienna, the Upper Lobau. A phosphorus budget and ecosystem metabolism measurements were used to assess the reaction of two trophically distinct floodplain backwater sections on changed connectivity conditions. The surface water connection led to a reduction of the retention times in the backwater system. The water column nutrient concentrations in the individual backwater sections approached those of the source water body. The significance of these effects, however, depends on the historical and current trophic situation of the respective water bodies. Generally, the surface water connectivity introduced particulate phosphorus export up to 30% increase over the influent loading and dissolved phosphorus up to 14% increase over the influent loading. However, in sections with submersed macrophyte development, which provided enhanced filtering capacities for particulate matter, sediment and phosphorus accumulation rates were increased. At the same time, water transparency increased resulting in a positive feedback supporting further macrophyte development. Based on these findings, the evaluation of restoration measures in urban floodplains needs to consider the spatial and temporal dynamics of nutrients and ecosystem processes such as gross primary production and community respiration to predict long-term development.

Educating for action: Aligning skills with policies for sustainable development in the Danube river basin.

Sustainable river basin management depends on knowledge, skills and education. The DANCERS project set out to identify feasible options for achieving education for sustainable water management across the Danube river basin, and its integration with broader education and economic development. The study traced the historic, regulatory and educational landscape of water management in the basin, contrasting it with the complex political decision-making, data-heavy decision support, learning-centred collaboration, and information-based participation that are all inherent components of Integrated Water Resource Management (IWRM). While there is a wide range of educational opportunities and mobility schemes available to individuals, there is no coherent network related to training in water management and sustainable development in the study region. Progress in addressing the multi-layered environmental challenges within the basin requires further aligning of economic, environmental and educational policies, advancing the EU Bologna Process across the region, and the development of dedicated training programmes that combine technical and relational skills. The DANCERS project identified key short and medium term needs for education and research to support progressive adoption of sustainable development, and the necessary dialogue across the public and private sectors to align policies. These include the development of new education networks for masters and PhD programmes, including joint programmes; improved access to technical training and life-long learning programmes for skills development; developing formalized and certified competency structures and associated accreditation of institutions where such skilled individuals work; and developing a co-ordinated research infrastructure and pan-basin programme for research for water management and sustainable development.

Decoupled water-sediment interactions restrict the phosphorus buffer mechanism in agricultural streams

Our study aimed to explore the effects of agriculture on the phosphorus buffer capacity of 11 headwater streams in Austria. We used phosphorus adsorption curves and re-suspension experiments to determine both, the potential of the sediments to act as phosphorus source or sink and the actual phosphorus exchange between water and sediments. Additionally, we determined the alkaline phosphatase activity (APA) in epilithic and epipsammic biofilms as indicator for the phosphorus demand of the benthic and hyporheic community. We hypothesized that highly polluted streams will show decreased phosphorus buffer capacities, which were either due to saturation or restricted water-sediment interactions. Our results support the second hypothesis. Fine sediment accumulations, organic matter content, and phosphorus concentrations in water and sediments increased with percent cropland in the catchment. Below SRP concentrations of 120μgL-1 in the stream water, sediments showed a high potential for phosphorus release, with zero equilibrium phosphorus concentrations (EPC0) being more than twice as high as SRP concentrations. Above 150μgL-1, EPC0 reached only 20-50% of SRP concentrations, indicating a high potential of the sediments to act as phosphorus sinks. These findings were confirmed by phosphorus uptake of these sediments during re-suspension. While APA in epilithic biofilms decreased with increasing SRP concentrations, APA in epipsammic biofilms showed the reverse pattern, indicating a restricted phosphorus supply of the hyporheic community despite phosphorus surplus in the water column. Our study shows that inputs of fine sediments from agricultural sources may reduce the phosphorus buffering mechanism of stream sediments through restrictions of water-sediment interactions. Consequently, water column and sediment processes are increasingly decoupled and phosphorus-rich stream water will not effectively reach the reactive sites in the sediments responsible for uptake. Therefore, phosphorus mitigation measures in stream ecosystems must comprise sediment management in the catchment as well as in-stream measures for the rehabilitation of the hyporheic zone.

Nutrient retention within the hyporheic zone of a low order sandstone stream (Weidlingbach, Lower Austria)

In this study at the Weidlingbach, a fourth order sandstone stream, the hydrological exchange between surface and interstitial water as well as the retention potential of the hyporheic zone for inorganic nutrients were studied. For this purpose, we performed shortterm nutrient additions (ammonium, nitrate, phosphate) at a 75 m long, third order study reach between May and August 2004. Additionally, hydrological and chemical parameters to estimate water exchange (VHG, hydraulic conductivity, conductivity, oxygen concentration) were measured in the stream and interstitial water. Sediments at the study reach could be divided into sites with either upwelling or restricted water exchange (low permeability, positive VHGs, low oxygen content) and sites which were characterized by a significant downwelling of surface water. Hyporheic nutrient uptake was measured at these latter sites. The nutrient with the highest retention efficiency was ammonium, followed by phosphate and nitrate. Vertical uptake curves indicated that the retention efficiency was highest in the sediments at the surface. These results imply that, at the Weidlingbach, the hyporheic zone does not considerably contribute to stream retention and that the surface sediments and the surface water play a greater role in nutrient cycling.

Phosphorus and Nitrogen Dynamics in Riverine Systems: Human Impacts and Management Options

Water chemistry constitutes one key factor for the ecological state of streams and rivers as it determines the composition of the media in which the aquatic organisms live. Among the various chemical substances dissolved in water, phosphorus (P) and nitrogen (N) are particularly important for the management of riverine systems. These two macronutrients are essential components of all organisms and are closely linked to the aquatic carbon cycle, determining both the primary production and the microbial mineralization of organic matter in aquatic systems. The industrialization and intensification of agricultural production during the twentieth century has resulted in the nutrient enrichment and eutrophication of many freshwaters in Europe and the USA, impairing the water quality of rivers, lakes, and aquifers (Grizetti et al. 2011). Among others, eutrophication is responsible for toxic algal blooms, water anoxia, and habitat and biodiversity loss in freshwater ecosystems and poses direct threats to humans by impairing drinking water quality (Smith and Schindler 2009). Nutrient enrichment causes severe problems in coastal zones and can even affect the climate through increased greenhouse gas emissions. Despite current improvements in wastewater treatment from industrial and municipal sources in Europe (Kroiss et al. 2005), phosphorus and nitrogen remain of concern for river managers especially in regions where intensive urban or agricultural land use results in pollution of aquatic systems through diffuse nutrient inputs. Diffuse sources challenge the management of nutrients in riverine systems by requiring a combination of mitigation measures on both the catchment and the reach scale (Mainstone and Parr 2002).

Public Participation and Environmental Education

Public participation can generally be defined as allowing people to influence the outcome of plans and working processes that constitute the operations of governance (CIS 2003). It can be practiced in different phases of integrated river basin management, but the public’s environmental understanding forms one basis for participation. Environmental education is the process of recognizing values and clarifying concepts in order to develop skills and attitudes necessary to understand and appreciate the interrelation among people, their culture, and their biophysical surroundings (Palmer 2003). In this chapter, we discuss how environmental education and public participation interact with and are influenced by each other and need to be embedded in all areas and levels of societal processes.

Danube Floodplain Lobau

Along the Upper Danube, almost all former floodplain areas have been lost due to river regulation, large-scale land-use changes, and terrestrialization processes. In the Lobau floodplain near the City of Vienna, ongoing terrestrialization leads to a dramatic loss of aquatic and semiaquatic habitats. Although the ecological values of the remaining floodplain area, such as high productivity and high biodiversity, are widely acknowledged, the implementation of restoration measures is difficult. In urban environments such as the Lobau, planning and decision-making for floodplain restoration inevitably involves tradeoffs, uncertainties, and conflicting objectives and value judgments. Beyond ecological values, the main socioeconomic aspects are flood control, drinking water supply for Vienna, and recreation.