Schutz ökologisch sensibler Fließgewässer: Konzepte und Fallbeispiele

European rivers are subject to heavy demand. In this regard, hydromorphological alterations in connection with energy production or flood protection measures are among the most serious issues. Today only very few natural or near-natural river reaches remain, and in Austria only 15% of the rivers are classified as being in “very good” and a further 22% percent as being in “good” ecological condition. In keeping with the objectives of the EU Water Framework Directive, the National River Basin Management Plan defines measures intended to achieve a good ecological status and/or avoid the further deterioration of Austria’s waterbodies.     

Die unbekannte dritte Dimension: Geländehöhen,Gewässertiefen und Dynamik österreichischer Donaulandschaften vor der Regulierung

River landscapes are multidimensional ecosystems characterized by diverse spatio-temporal interrelations. Longitudinal interactions along the river continuum and lateral exchange processes between river and floodplain are common focal points in river restoration projects. Vertical interactions, such as between aquatic habitats and river bottom (hyporheic interstitial) or between groundwater and terrestrial habitats, are often only addressed in planning schemes, if the impairments of ecological functions and human uses are already evident. This partly reflects the dearth of well-founded basic data on the configuration of river landscapes prior to regulation in the vertical dimension. Consequently, only few reference data are available for designing adapted restoration measures.     

Vergleich von Verfahren zur Rückgewinnung von Phosphor aus Abwasser und Klärschlamm

Phosphorus (P) is a vital but limited resource. Though Austria has no P deposits, municipal wastewater offers a potential but largely overlooked source of phosphorus. Over the last several years, numerous technologies have been developed for recovering P from various streams at a wastewater treatment plant. This work uses an approach developed by the authors to assess these technologies on the basis of technical, ecological and economic criteria, providing a basis that legislators and political decision-makers can orient a future, optimized P management system on. The study shows that e.g. technologies for recovering P from process water are already available, and that under the right circumstances they can be used to affordably deliver a high-purity, plant-available end product; however, the potential for P recovery is relatively low. In order to arrive at maximal utilization of the phosphorus from wastewater, the future focus should be on recovery from sewage sludge ash. In this regard, mixing with low-phosphorus ash should be avoided. At this time, however, the necessary structures like e.g. monoincineration plants still need to be expanded. Which technology/ technologies will ultimately be used for the treatment of sewage sludge ash depends e.g. on considerations of affordability, heavy metal elimination, and the plant-availability of the P recovered. The advantages of a strategy based on “monocombustion” of sewage sludge are on the one hand the option of using further P-rich material flows (e.g. meat and bone meal) and on the other, the freedom to store the ash for future recovery (creating an Austrian “phosphate mine”).     

Probleme bei Planung und Betrieb von Absetzbecken für Straßenabwässer

Sedimentation basins are incorporated into runoff infiltration systems and serve as a retention system, in which the sedimentation of particles occurs as a result of gravitational force. The effectiveness of sedimentation basins in terms of removing particles is highly dependent on design parameters such as their dimensions and drainage times. To evaluate the flow distribution within sedimentation basins, a conceptual model was developed using a tracer and compared to the actual condition at the treatment system. Here, a significant difference in the height of the connecting tube between settling basin and filter basin was found. This leads to a drying out of the basin, which significantly affects the flow rates and hence the sedimentation there. Based on a model experiment with colour tracer, the flow paths were visually represented in the basin, and both the concrete variant and the effects of internal structures were considered. It was found that the incorporation of a baffle led to an improved utilization of the basin, and to water being retained for longer times. Due to the lower flow rate and these longer times, fine and medium-sized sediments could be easily settled. In a field study, the performance of a sedimentation basin for the removal of particles was evaluated based on the influent and effluent concentrations of total suspended solids (TSS). The street runoff treatment plant was monitored for one year and results showed that there was no particle accumulation in the sedimentation basin (there was no permanent retention of the particle loads). The mean TSS concentrations were 89 mg/L at the inlet of the sedimentation basin and 94 mg/L at the end of the settling tank, respectively. The structural design and operation of the system showed higher flow and turbulent flow conditions in the sedimentation basin, in which settlement of fine and medium sized particles was very low; as a result, the soil filter basin was loaded with runoff particles. Thus the particulate matter had to be removed either on the surface of the filter basin or within the porous space of the filter. The build-up of such particles can result in a significant increase of head loss due to clogging; therefore, filters must be maintained by removing the accumulated particles on a regular basis.     

Klimawandel,Stadtentwicklung und urbane Wasserinfrastrukturplanung – Risiken und Möglichkeiten

The sealing of surfaces and changes in land use as a result of population developments, as well as an ageing infrastructure, present new challenges for urban water management. Changes in catchment areas are mirrored by changed flood risks, even in areas not previously affected. A comprehensive analysis of scenarios is indispensable in achieving forward-thinking planning and adapting existing water infrastructures to better reflect current changes and the dynamics of the urban setting. Not only are urban areas themselves constantly changing; climate-related changes can significantly influence urban water infrastructures. In this regard, torrential rains that only impact small areas are especially important.The results of analyses confirm the necessity of taking into account multiple urban development scenarios, in combination with climate change prognoses, in order to accurately determine the risks for potentially problematic areas in the network.     

Dezentrale Aufbereitung und Lagerung von Speiseresten – Neue Wege zur Ressourcen- und Energiespeicherung

Organic waste, especially kitchen and canteen waste, is produced in large quantities and is subject to considerable fluctuations, both in terms of its composition and quantity, due in part to changing seasonal factors. Kitchen waste commonly undergoes biological and primarily anaerobic waste treatment (fermentation), producing both material (digestate, fertilizers and soil conditioners) and energy resources (biogas, electrical and thermal energy). The introduction of decentral collection and treatment systems promises to offer new solutions with regard to resource and energy storage, and with regard to compensating for the previously mentioned fluctuations. Within this study kitchen waste was initially pretreated and processed at laboratory scale. Subsequently, the influence of storage at 5, 20 and 30?°C for a period of 28 days was investigated. It was determined that, when stored, acidification and a corresponding drop in pH value promptly set in. The higher the temperature, the higher the level of acidification and the higher the concentration of organic acids became. In order to analyze the effects of storage on kitchen waste as an energy source, its biogas potential was measured in correlation with storage duration and temperature. Neither factor proved to have any significant influence on gas yield. Due to acidification, which can be seen as a chemical decomposition process, stored substrates produced up to 20?% higher gas yield compared to the original substrate. Accordingly, unavoidable kitchen and canteen waste can be considered valuable energy sources, which can contribute to efficient and needs-oriented energy production.     

Die Bauwerksdatenbank der Wildbach- und Lawinenverbauung: Nutzen für Gemeinden und Wassergenossenschaften

For nearly a decade, the Austrian Service for Torrent and Avalanche Control (Wildbach- und Lawinenverbauung (WLV)) has maintained the digital torrent and avalanche register, which brings together all relevant data concerning catchment areas, projects, hazard zone plans, certifications and natural events. The register also includes a database on protective structures (the structures module), in which every WLV structure is listed, along with its location and a fact sheet detailing its essential information. In the course of status assessments, the current condition of each structure is determined. Given the fact that, as laid out in the corresponding legislation, the responsibility for maintaining protective structures following their initial certification lies with the operators and other stakeholders (as a rule, municipalities and water associations), those structures’ current status is of considerable interest to these groups. Structures can only fulfill their protective function if their functionality has been ensured and is checked on a regular basis. In the future, the structures module could offer an important instrument for those parties responsible for maintenance, helping them to monitor the various protective structures, and to plan urgently needed repair measures in an efficient and timely manner. The following paper addresses the WLV’s basic maintenance principles, as well as the significance of its torrent and avalanche register in connection with the responsibility for maintenance.     

Bemessung und Überwachung von Beschneiungsspeichern

Reservoirs for artificial snow production are playing a key role in winter tourism. In order of their almost exposed site and large reservoir capacity high efforts on their structural and operational safety have to be carried on. That means that reservoirs have to be designed very conservative, realised with high quality and supervised by representative parameters of their behaviour. At site inspections are carried out by personal (dam attendant, dam safety engineer) which is well educated and familiar with the reservoir and the appurtenant structures. For this task additional workshops and courses are provided to prepare personal best possible for that high responsible function. Besides the regulations of the Austrian Water Law and the decisions of the Austrian Commission on Dams in 2011 a guideline was finished for external use, which stipulates the requirements on reservoirs for artificial snow production and other applications (Approval Procedure, Procedure for the Renewal of the Permit) and constitutes thereby an uniform and throughout Austria valid standard.     

Ausmaß und Dynamik der Sohlerosion der Donau östlich von Wien – flussmorphologische und wasserwirtschaftliche Aspekte

The Danube east of Vienna was originally an untamed, widely branching river with an approximately stable bed elevation. Regulation in the second half of the 19th century changed its morphology fundamentally—initially through upstream regulation and the consequent bedload deposit resulting in heavy aggradation—and subsequently left the bed elevation and water level almost the same until around the 1940s. Only in the second half of the 20th century did the bed elevation and low and mean water levels decrease significantly, and this trend—amplified by the power plant extension—continues today, despite constant bedload dumps to ensure the tailwater supply for the power plant at Vienna Freudenau. Further east from the Austrian-Slovak stretch of border, congestion due to the Gab?íkovo power plant becomes apparent: most of the bedload is again deposited here. This study investigates these processes using hydrographic observations in their spatial and temporal context, and, based on actual bed elevation measurements, creates a bedload balance and compares it with the results of previous studies. Bed erosion in the Danube floodplains and the local national park has far-reaching consequences, especially through siltation and scrub encroachment in the river’s branches, which are further amplified by flat, fine sediment deposits in the foothills and the formation of embankments. In the long term, flood and other water management objectives will also be adversely affected.     

Asphaltoberflächendichtung für Speicher von Beschneiungsanlagen

Asphalt seal coating for snow reservoirs provides a technologically proven, stable seal with negligible water loss. As this approach is compatible with steep upstream slopes, the maximum volume can be exploited. Given the geology of mountain areas, there are few suitable locations for reservoirs; as such, maximizing the usable water volume with the help of asphalt seal coating offers an economical solution.     

Klimawandel und Urbanisierung – wie soll die Wasserinfrastruktur angepasst werden?

Conventional urban water servicing has successfully provided cities with clean water, sanitation and flood protection. Traditional approaches are unsuited to address future challenges like climate change and modern urban development trends (e.g. migration, aging population, densification). As well as increased risks of water scarcity and flooding, society's demands for urban amenity and healthy waterways in metropolitan areas also challenge these traditional principles of urban water management. It is increasingly recognized that solutions to these challenges will not be purely technological in nature; the socio-institutional contexts will also be critical. However modelling tools to support medium and long-term strategic planning of integrated social and infrastructural dimensions are lacking, leaving decision-makers with untested policy ideas. To identify possible transition strategies to a resilient city, the development of the DAnCE4Water (Dynamic Adaptation for eNabling City Evolution for Water) within the EU FP7 project “PREPARED: Enabling Change” as a strategic planning and decision-support tool is thus proposed. DAnCE4Water allows ‘What-if’ experiments by investigating possible consequences of policies and strategic actions, taking into consideration urban development, climate change, biophysical environment and societal dynamics. This paper presents the concept of the DAnCE4Water tool and its application to an example city's evolution 20 years into the future.     

Indikatorenbasierte Evaluierung von Fischhabitaten in alpinen Fließgewässern

The EU Water Framework Directive commits member states to achieve good ecological status in all waterbodies. Artificial or heavily modified waterbodies must reach at least its good ecological potential. In view of these requirements, simple and feasible methods are required in order to evaluate habitat suitability for relevant target species in larger river reaches. Well-developed models for determining the relationship between stream flows and habitat for target species mainly based on micro- and meso-scale already exist. However, the application of such models is complex and time-consuming and consequently limited to relatively short river segments. The objective of this study is to develop a simplified applicable assessment model to evaluate habitat conditions for selected target fish. This model uses hydro-morphological indicators for the habitat assessment and relies on correlative relations between habitat suitability and hydro-morphological features of river stretches (average Froude-number, relative flow width, mean bed slope, relative water depth and flow velocity). The indicators were determined as reach-related averages, derived from 2D model simulations (hydraulic and habitat-specific). Particular emphasis was laid on using a wide range of river stretches with different hydro-morphological characteristics (hydrology, bed substratum, bed structures, degree of braiding, sinuosity of the river course, mean bed width and bed slope). As a result, a set of model equations enables the evaluation of fish habitat conditions in river stretches as a function of flow and morphology. The habitat suitability assessment focuses on four preselected target species: brown trout, European grayling and for low slope rivers common nase and barbel.     

Integratives Schwebstoffmonitoringkonzept – Innovative Ans?tze auf Basis direkter und indirekter Methoden

This work presents the Austrian monitoring strategy for measuring suspended sediment transport in rivers, the application of which is mandatory at the measurement sites of the Austrian monitoring network provided by the hydrological service and which was published in ??Suspended sediments in rivers??guidelines for the monitoring of suspended sediments.?? In order to determine the temporal and spatial variability of the suspended sediment transport a combination of direct and indirect methods is used. The monitoring methods applied and their interrelation during the data processing via correction factors are described. The monitoring concept was implemented at the Hainburg Stra?enbrücke/Donau measurement site, where a comparison involving different conversion factors was performed. The results of annual and monthly load calculations are presented for the years 2008 and 2009     

Monitoring,Analyse und Interpretation des Schwebstofftransportes an österreichischen Flüssen

In recent years the Austrian Hydrographic Service has developed and implemented a new system for continuous and long-term suspended sediment monitoring, one which takes into account the spatial and temporal variability of the suspended sediment transport process in order to provide long-term datasets on concentrations and transport rates. The data gathered is thoroughly checked in terms of its quality and released annually. The suspended sediment concentrations, transport rates, loads and yields at 28 measuring sites were analyzed for the period from 2009 to 2011. The results allow us to make conclusions about the respective suspended sediment transport processes in Austrian catchments.     

Grundlegende Erkenntnisse im Rahmen des Pilotprojekt Bad Deutsch-Altenburg – Die Bedeutung der Stromsohle und Uferzonen für ökologische Prozesse und Artengemeinschaften an einem stark regulierten Fluss,der Donau

To ensure a long-term ecological stability, rivers need areas that are available at different discharge situations as highly productive habitats which are connected with the river. These retention areas or biologically active zones are important for the riverine communities as refuge (e.g. benthic macroinvertebrates and fish) or the development of benthic algae communities as basis for the riverine food web as well as retention zones to perform various ecosystem services (e.g. nutrient retention). Especially during low water level situations, the river shorelines and the river bed itself are of significant importance, but highly degraded in intensely regulated river systems such as the Danube River. A basic understanding of the processes and functional correlations is required to avoid negative consequences of engineering measures applied and to improve the ecological conditions. In the framework of the pilot project Bad Deutsch-Altenburg in the Danube River east of Vienna not only monitoring the implementation of engineering measures is required, but also scientific knowledge gained about basic ecological relationships and potential responses of riverine communities. This article presents results of several years of investigations on the distribution and development of three organism groups (benthic algae, benthic macroinvertebrates and fish) along different riparian structures and in the river bed of the Danube River.     

Das nutzbare Potenzial biologischer Siedlungsabfälle zur Erzeugung biobasierter Produkte – Beispiel Kompostwerk

From September 2013 to May 2014, a feasibility study was conducted in collaboration with the Enterprise for Municipal Services (Eigenbetrieb für kommunale Aufgaben und Dienstleistungen (EAD)), Handelshaus RUNKEL, the engineering firm INGUT, JAGER BIOTECH GmbH and the TU Darmstadt (Research Area: Waste Engineering), the goal of which was to determine whether biological waste produced by the city of Darmstadt could be used to create a fuel on the basis of non-polar carboxylic acids.     

Untersuchung der Funktion von Leichtflüssigkeitsabscheidern bei Verwendung von Kraftstoffen mit unterschiedlichen FAME-Zusätzen

The use of biogenic additives in fuels is required by law for environmental reasons. This raises the question of whether the oil separator tested according to ÖNORM EN 858-1 complies with these new requirements. In this study, a commercial mineral oil separator was tested with different fuels with up to 100?% biodiesel (FAME) and its elimination performance was described in terms of the parameters KW, KW-Index DIN EN ISO 9377-2 H 53 (2000), and also the non-standardized parameters for mineral oil analysis in accordance with H 18 and H 53 without the purification stage. The results showed that all the tests with different fuel mixtures complied with the test value of 5 mg/l laid out in EN 858-1 (2005) and based on the parameter mineral oil analysis in accordance with DIN 38409-H 18 (1981). As the purification stage of this method removes the biofuel fraction, the question arises as to whether fuels with increased biogenic content can be analyzed satisfactorily using these standardized mineral oil parameters; and whether the use of pure mineral oil for ÖNORM EN 858-1 (2005) performance tests is still suitable, or whether other fuels should also be used as test media.     

Ecosystem-based fisheries management is attainable,affordable, and should be viewed as a long-term commitment: Experiences from Lake Vättern,Sweden

Lake Vättern is Sweden’s second largest lake and faces multiple environmental challenges such as climate change, pollutants and invasive alien species. Since its foundation in 1957, the Lake Vättern Society of Water Conservation (LVSWC) has been a local actor aiming to manage a broad range of environmental issues concerning the lake and its catchment. Stakeholders can be members of LVSWC, which also organises a fisheries co-management group mainly dealing with fisheries issues. Ecosystem-based fisheries management (EBFM) is a widely desired framework shaped to focus on ecosystems, involve stakeholders, and address environmental issues in an adaptive, integrated and holistic manner while also including societal aspects. We have investigated how the management of Lake Vättern relates to 15 central principles for EBFM. The study found that LVSWC and the fisheries co-management group work along and towards the EBFM principles in a locally adapted way. Several environmental improvements have been observed concurrently with LVSWC activity, such as increased water clarity, and a strengthened stock of the Arctic char (Salvelinus alpinus). Long-term commitment by European, national and regional authorities was seen as essential to maintain and improve EBFM functions for Lake Vättern, to ensure continuity in the work, rather than having to depend on short projects. Becasue literature examples of EBFM in lakes are scarce worldwide, this study provides a unique example of the pursuit of EBFM in lake ecosystem management.