Silke Wieprecht

Anthropogenic Trace Compounds (ATCs) in aquatic habitats - research needs on sources, fate, detection and toxicity to ensure timely elimination strategies and risk management.

Anthropogenic Trace Compounds (ATCs) that continuously grow in numbers and concentrations are an emerging issue for water quality in both natural and technical environments. The complex web of exposure pathways as well as the variety in the chemical structure and potency of ATCs represents immense challenges for future research and policy initiatives. This review summarizes current trends and identifies knowledge gaps in innovative, effective monitoring and management strategies while addressing the research questions concerning ATC occurrence, fate, detection and toxicity. We highlight the progressing sensitivity of chemical analytics and the challenges in harmonization of sampling protocols and methods, as well as the need for ATC indicator substances to enable cross-national valid monitoring routine. Secondly, the status quo in ecotoxicology is described to advocate for a better implementation of long-term tests, to address toxicity on community and environmental as well as on human-health levels, and to adapt various test levels and endpoints. Moreover, we discuss potential sources of ATCs and the current removal efficiency of wastewater treatment plants (WWTPs) to indicate the most effective places and elimination strategies. Knowledge gaps in transport and/or detainment of ATCs through their passage in surface waters and groundwaters are further emphasized in relation to their physico-chemical properties, abiotic conditions and biological interactions in order to highlight fundamental research needs. Finally, we demonstrate the importance and remaining challenges of an appropriate ATC risk assessment since this will greatly assist in identifying the most urgent calls for action, in selecting the most promising measures, and in evaluating the success of implemented management strategies.

A neuro-fuzzy-based modelling approach for sediment transport computation

Abstract The application of a data-driven adaptive neuro-fuzzy modelling technique for predicting bed load and total bed-material load for the River Rhine is summarized. Four main parameters affecting sediment transport are used to construct the model, using 560 and 510 measured bed load and total bed-material load data, respectively. Two-thirds of the available data sets are used for training and one third for testing. The initial fuzzy model is obtained by grid partitioning of the input variables. The optimization of the model is performed by data-driven tuning of the fuzzy model parameters using the adaptive neuro-fuzzy inference system, so that the model output is able to reproduce the measured value. A sensitivity analysis for the combination of input parameters, as well as the number and type of membership functions, is also performed. The model results show that the data-driven adaptive neuro-fuzzy modelling approach can be a powerful alternative technique for estimating both bed load and total bed-material load. Editor D. Koutsoyiannis Citation Wieprecht, S., Tolossa, H.G., and Yang, C.T., 2013. A neuro-fuzzy-based modelling approach for sediment transport computation. Hydrological Sciences Journal, 58 (3), 587–599.

A multi-disciplinarily designed mesocosm to address the complex flow-sediment-ecology tripartite relationship on the microscale

BackgroundThe stabilization of fine sediments via biofilms (‘biostabilization’) has various economic and ecological implications but is presently unaddressed within lotic waters. To investigate natural biofilm growth and functionality in freshwater sediments under controlled boundary conditions, a unique mesocosm was constructed that combines established know-how from engineering and natural sciences and consists of six straight flumes. To test the comparability of biofilm growth within one flume and between the flumes, extracellular polymeric substances (EPSs), microbial biomass and microbial community composition were closely monitored over time and space as well as in relation to biofilm adhesiveness (proxy for biostabilization).ResultsMost importantly, biofilm development and biostabilization capacity revealed no significant differences within flume regions or between the flumes and the biofilms significantly stabilized the substratum as compared to abiotic controls. However, interesting temporal successions in biofilm growth phases became visible in shifting abundance and diversity of bacteria and microalgae resulting in varying EPS secretion and biostabilization.ConclusionsThese findings demonstrated the importance of biostabilization for fine sediment dynamics in freshwaters. Secondly, this unique setup allows comparable biofilm growth under controlled environmental conditions, an important requisite for future research on the ecological significance and impact of biostabilization for ecosystem functioning at varying environmental scenarios.

Extreme Events, Critical Infrastructures, Human Vulnerability and Strategic Planning: Emerging Research Issues

The importance of critical infrastructures and strategic planning in the context of extreme events, climate change and urbanization has been underscored recently in international policy frameworks, such as the Sustainable Development Goals (SDGs), the Sendai Framework for Disaster Risk Reduction 2015–2030 (UNISDR (United Nations/International Strategy for Disaster Risk Reduction) 2015), and the new Paris climate agreement (UNFCCC (United Nations — Framework Convention on Climate Change) 2015) as well as the New Urban Agenda (UN-HABITAT 2016). This paper outlines key research challenges in addressing the nexus between extreme weather events, critical infrastructure resilience, human vulnerability and strategic planning. Using a structured expert dialogue approach (particularly based on a roundtable discussion funded by the German National Science Foundation (DFG)), the paper outlines emerging research issues in the context of extreme events, critical infrastructures, human vulnerability and strategic planning, providing perspectives for inter- and transdisciplinary research on this important nexus. The main contribution of the paper is a compilation of identified research gaps and needs from an interdisciplinary perspective including the lack of integration across subjects and mismatches between different concepts and schools of thought.

The effect of light intensity and shear stress on microbial biostabilization and the community composition of natural biofilms

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An overview of hydro-sedimentological characteristics of intermittent rivers in Kabul region of Kabul river basin

ABSTRACT Intermittent rivers are defined as rivers with a high seasonality in water, sediment transport and habitat. In this study, an attempt is made to outline the major hydro-sedimentological characteristics of intermittent rivers systems using the examples from the Maidan and Shakar-Dara rivers in Kabul region of the Kabul river basin. As dominant hydrological characteristics of intermittent rivers, the interaction between surface water and groundwater is studied by correlating the precipitation, evapotranspiration, river discharges and groundwater level fluctuations in wells located in the vicinity of the rivers. Suspended sediment transport and river bed sediments are in a further step studied to understand the sedimentological behaviour of these river systems. The characteristics of the catchment area such as geology, land cover, land use and dry periods are studied to show their influence on the suspended sediment transport. Field observations and satellite images are used to investigate the morphology of the selected rivers. Results show that precipitation, in particular during the winter and early spring months exceed the evapotranspiration and are providing the main water source for irrigation and groundwater recharge. The analysis reveals that the seepage loss through the river bed contributes significantly more to the groundwater recharge than precipitation. An increase in suspended sediment concentrations in Maidan river are observed by comparing historic (1965–1968) and recent (2012–2015) data. In addition, higher suspended sediment concentrations are observed in Maidan river compared to Shakar-Dara river. The higher concentrations can be linked to the lower percentage of vegetated area in its catchment compared to the Shakar-Dara catchment as well as to its finer sediment grain sizes of its bed and banks. Morphological investigations indicate single and multi-thread (braided) channels are the most common planform types for Shakar-Dara river, however, at Maidan river with gentle slopes, a meandering tendency with various sinuosities can be observed.

Bewertung der Versagenswahrscheinlichkeit von Staustufenstandorten mit Bayesschen Netzen

Stauanlagen sind künstliche Bauwerke zur Regulierung des natürlichen Abflusses an Gewässern. Diese Anlagen dienen im Falle der Wasserkraftnutzung der Industrie, im Falle der Beund Entwässerung der Landwirtschaft sowie als Verkehrsträger der Schifffahrt. Staustufen spannen, im Gegensatz zu Talsperren, im Wesentlichen nur über die Flussbreite und nicht über die gesamte Talbreite (Bild 1). Staustufen sind verschiedensten Einflüssen ausgesetzt, wie beispielsweise normalen Abflussverhältnissen, Hochwasser ggf. mit Treibgut, plötzlichem Turbinenschnellschluss, einer Störung bzw. einer Revision von Verschlüssen, Windereignissen, Frost und Eis oder Erdbeben. Gemäß DIN 19 700-13 [1] sind Staustufen auf diese Einwirkungen auszulegen. Im Jahr 2004 wurde in dieser Norm eine Klassifizierung in drei Klassen mit abgeleiteten Ansprüchen an das Bemessungshochwasser eingeführt. Eine Staustufe mit einer Fallhöhe bei MQ kleiner gleich 3 m ist demnach in Klasse 3 einzuordnen und eine Staustufe mit einer Fallhöhe größer 5 m in Klasse 1. Weiter sind Anlagen an schiffbaren Gewässern und Anlagen, bei denen im Falle eines Anlagenversagens Siedlungen gefährdet sind, in Klasse 1 einzuordnen. Die letztgenannte Regel bedeutet u. a. für den Anlagenbetreiber eine Auseinandersetzung mit dem Risiko, das von der Staustufe ausgeht, und damit die Erfordernis, die Wahrscheinlichkeit für „den Fall eines Anlagenversagens“ zu erfassen. Damit stellen sich verschiedene Fragen, beispielsweise welche Prozesse zu einem Anlagenversagen führen, wie wahrscheinlich dies ist und, wenn die Versagenswahrscheinlichkeit bekannt ist, wie sich diese effizient reduzieren lässt. Der folgende Beitrag nimmt die vorstehenden Fragen auf und führt ein Bayessches Netz zur quantitativen Bewertung von Staustufenbetrieb und -überwachung ein [2]. In diesem Zuge fließen die Ergebnisse einer Befragung zur Staustufenüberwachung von rund 100 Anlagenbetreibern ein. Im Fokus dieses Artikels stehen damit Staustufen mit einer Fallhöhe bei Mittelwasserabfluss von 0,3 bis 39 m (Median rund 5 m) und einem Ausbauabfluss der Wasserkraftanlage von 0,3 bis 3 000 m3/s (Median 20 m3/s). Der Median der Jahreserzeugung der in der Betreiberbefragung vertretenen Wasserkraftstandorte beträgt 3,5 GWh/a. Für Sicherheitsbewertungen sind Ereignisund Fehlerbäume Stand der Technik. Bayessche Netze stellen eine zeitgemäße Erweiterung dieser statistischen Methoden dar und ermöglichen einen anschaulichen sowie intuitiven Zugang zu komplexen Themen und Zusammenhängen. Ein solches Bayessches Netz wird für die Sicherheitsbewertung von Staustufen vorgestellt. Das Netz bildet die Versagensmodi Überflutung sowie strukturelles Versagen des Stauhaltungsdammes und der Wehranlage ab und ermöglicht die Bewertung des Einflusses der Konstruktion, der Überwachung sowie des Betriebs dieser Bauwerke auf die Anlagenversagenswahrscheinlichkeit. Bewertung der Versagenswahrscheinlichkeit von Staustufenstandorten mit Bayesschen Netzen

New insights into MagPI: a promising tool to determine the adhesive capacity of biofilm on the mesoscale

Abstract The adhesiveness and stability of ubiquitously distributed biofilms is a significant issue in many areas such as ecology, biotechnology and medicine. The magnetic particle induction (MagPI) system allows precise determinations of biofilm adhesiveness at high temporal and spatial resolution on the mesoscale. This paper concerns several technical aspects to further improve the performance of this powerful experimental approach and enhance the range of MagPI applications. First, several electromagnets were built to demonstrate the influence of material and geometry with special regard to core remanence and magnetic strength. Secondly, the driving force to lift up the particles was evaluated and it was shown that both the magnetic field strength and the magnetic field gradient are decisive in the physics of the MagPI approach. The intricate combination of these two quantities was demonstrated with separate experiments that add permanent magnets to the MagPI system.

An Evolution Volume Balance Approach to Determine Relevant Discharge Threshold for Bed Load Transport

The aim of this study is to investigate discharge rates at which a flow hydrograph becomes relevant for bed load transport on the example of the Alpine river Saalach. Two characteristic flow hydrographs of the river Saalach are selected and reduced to discharges above pre-specified values. With each set of reduced hydrographs, a 2D morphological simulation is conducted. Two important morphological parameters, namely total river bed evolution (i) and sorting effects of the active layer (ii) are analyzed and evaluated. Moreover, an additional simulation is conducted with a linearly increasing flow hydrograph as boundary condition to analyze the initiation of bed load transport as a function of discharge (iii). The results are analyzed and evaluated with respect to the total sediment output at the downstream boundary of the model and at some inner control sections to validate the findings for (i) and (ii). The model results show: (i) For regions with fine bed materials, discharge thresholds between 100 and 130 m3/s and for regions with mainly coarse bed materials discharge thresholds in the range between 150 and 180 m3/s can be identified as relevant discharges for bed load transport and may be used for reducing hydrographs without affecting the accuracy of the model results; (ii) The active layer shows no obvious changes in the mean diameter of sediments for all tested hydrographs. (iii) The investigations with a linearly increasing flow hydrograph show that the sediment output from the investigated river reaches increase significantly for discharges exceeding 150 m3/s.

Planung der Fließgewässer- und Auenentwicklung

Dieses Kapitel zeigt, dass die Grundlage einer erfolgreichen Fliesgewasser- und Auenentwicklung die naturraumangepasste Planung unter Berucksichtigung wasserwirtschaftlicher, gewasserokologischer und naturschutzfachlicher Grundlagen ist. Eine Besonderheit stellt dabei die Planung im urbanen Umfeld dar. Einflusse auf die Entwicklungsprozesse im Wasserkorper und auf den gewassernahen Flachen (Uferstreifen und Gewasseraue) hat dabei im besonderen Mase die Fliesgewasserunterhaltung. Eine umfassende Offentlichkeitsbeteiligung verbessert die Akzeptanz jeder Masnahme. Die Finanzierung ist eine Grundvoraussetzung fur die Realisierung eines Projektes. Hierzu werden in diesem Kapitel einige Beispiele vorgestellt.