German Federal Waterways Research Articles

Prescriptive analytics for low and high water management in German waterways

Abstract The real-time management of multi-purpose storage reservoirs aims at an efficient operation of existing hydraulic infrastructure. This management process can be structured as a prescriptive analytics setup that considers both current and predicted system states to recommend actions and outline potential implications. In application to a reservoir and river system, it combines hydrological modelling components for the system schematization, observations and data assimilation for the identification of the current system state, meteorological and hydrological predictions as well as optimization-based techniques to support decision-making regarding reservoir operations. In this paper, we present the application of such a framework to the short-term management of the Eder and Diemel storage reservoirs. These reservoirs are operated by the German Federal Waterways and Shipping Administration (WSV) with the primary goal to support navigation in the River Weser during low flow periods. In addition, partially conflicting objectives such as flood protection, energy generation and recreation are considered. The implementation includes an explicit consideration of forecast uncertainty and its impact on the decision-making by using probabilistic forecasts in combination with a multi-stage stochastic optimization approach. We demonstrate the applicability of the approach based on low and high water use cases. Special attention is paid on the benefits of the probabilistic forecast in combination with the multi-stage stochastic optimization versus a deterministic setup. It provides an explicit translation of the forecast uncertainty in the decision variables, in this case the reservoir releases helping the operators to better anticipate the range of future release decisions. Furthermore, the stochastic approach is expected to provide more stable decisions in an operational setting, based on more stable forecasts by considering various possible realizations of the future instead of picking a single one, which gets random after 4–5 days.

Climate Change Impacts on Soil Erosion and Sediment Delivery to German Federal Waterways: A Case Study of the Elbe Basin

Climate change is an important driver of soil erosion and sediment delivery to water bodies. We use observation data from 193 locations in the Elbe River basin as well as spatially distributed erosion rates and sediment delivery simulated in the WaTEM/SEDEM to identify current erosion hotspots and to assess the impact of climate change on future erosion and sediment delivery. We further quantified the uncertainty of the modelling approach by using an ensemble of 21 combinations of global and regional climate models, different emission scenarios and stochastic erosion modelling. Erosion rates are highest on hilly arable land in the central part of the basin as well as in the northeast of Bohemia. Despite considerable differences between climate models and emission scenarios and considerable uncertainties of the erosion model, a future increase in soil erosion and sediment delivery is highly likely. Using the median of climate models and behavioral erosion models, this increase can be up to 14% higher in the far future (2071–2100) than in the reference period (1971–2000) using RCP 8.5. The increase is highest in the Czech part of the basin.

Germany’s federal waterways – A linear infrastructure network for nature and transport

Major rivers are unique linear structures because they serve different purposes simultaneously: A habitat and dispersal route for flora and fauna as well as a navigation route, the site for recreational and economic activities and a source for drinking water and irrigation. In recent years, it has become increasingly clear that waterways must be developed in an environmentally and economically sustainable and socially responsible manner. The Federal Ministry of Transport and Digital Infrastructure (BMVI) and its specialised agencies – the Waterways and Shipping Administration of the German Federal Government (WSV), the Federal Institute of Hydrology (BfG) and the Federal Waterways Engineering and Research Institute (BAW) – are aiming to achieve this goal by integrating environmental issues into the development and maintenance of waterways. This paper aims to fill the gap on the one hand between scientific analyses of ecological freshwater status and proposals for its improvement, and, on the other hand, bringing this knowledge into practical realisation. Recent activities at the German federal waterways are exemplarily reviewed on the basis of applied research projects, local projects, political programmes and progressive legislation.

Assessment of maintenance efforts and probabilities of failure at German inland waterways to advance the design of bank revetments

Revetments protect waterways or flood defenses against erosion from waves and currents. In Germany a high percentage of about 7235 km of waterways is secured by revetments. Like many stakeholders of various infrastructures, the German Federal Waterways and Shipping Administration increasingly aims for a more economic and ecological design and maintenance strategy. Thus, new methodologies must be introduced that relate the structural condition of the revetment to resulting consequences such as required maintenance. In this paper we investigate the correlation of maintenance and revetment stability. Using the example of German inland waterways, maintenance measures conducted over at least six years are correlated with a deterministic and a probabilistic stability assessment. To account for realistic traffic loads, the stability assessment employs field measurements which provide data on ship-induced waves. It was found that at least a linear correlation between revetment stability and maintenance must be assumed. A comparison between the deterministic and the probabilistic stability assessment and thereby obtained correlations shows that less maintenance is predicted with the deterministic stability assessment. Particularly for small sample sizes and small probabilities of failure, the probabilistic approach should be favored over the deterministic approach to account for various uncertainties. In the case that only maintenance is of relevance for design considerations, the results of the probabilistic approach indicate that β = 1.3 (pf ≈ 10-1) may be a suitable annual target reliability.

Establishing (e)DNA-Methods for Governmental Biomonitoring Efforts and Ecological Assessment in German Federal Waterways

The German Federal Institute of Hydrology (BfG, for its acronym in German) is the nationwide advising departmental research institution regarding hydrology, water use and quality, ecology and water protection of the German Federal Waterways that comprise inland waterways as well as marine coastal waters. The Federal Waterways of Germany are important habitats and distribution corridors for aquatic biodiversity. However, the ecology of these large rivers is heavily impacted by shipping, hydromorphological alterations, chemical pollution and the distribution and establishment of invasive species. All these factors have led to a decline of native biodiversity and ecological status. Since the 1970s, tremendous efforts have been undertaken to restore water quality and biodiversity. Continuous monitoring and assessment of both chemical components and biological quality elements (BQEs) required by law should indicate the success or failure of restoration measures as well as ongoing and future ecological consequences of multiple stakeholders’ interests and demands. Standardized ecological assessment procedures are already in place for both rivers and streams. However, these widely used procedures have several shortcomings and require a high level of taxonomic competence, which is being lost at an increasing rate. DNA and environmental DNA (eDNA)-based methods, such as DNA barcoding and (e)DNA metabarcoding, are promising alternatives to overcome the impediments to the morphology-based identification of organisms. But, these new methods need to be tailored to the challenges of large river bioassessment. The implementation of such state-of-the-art methods for future biomonitoring and ecological assessment efforts in large rivers should therefore ultimately serve the legal requirements regarding the EU Water Framework Directive (WFD) and promote the application of (e)DNA methods from basic and applied research to water managers and regulatory authorities. Here we present the goals and approaches of our ongoing project that are 1) to create standard operation procedures (SOPs) for (e)DNA analyses for large rivers and 2) update or establish new methods for biodiversity assessment and biomonitoring (e.g. presence-absence analyses) of the federal waterways; and 3) to transfer the gained knowledge to water managers and practitioners. To accomplish these goals, the focus of our research relies on the BQEs fish and macrozoobenthos (led by Saskia Schmidt), as well as phytobenthos and phytoplankton (led by Demetrio Mora).

Overhaul of solid construction locks in German federal waterways

The predominant part of the navigable inland waterways in Germany was developed between the end of the nineteenth and the middle of the twentieth century. The main hydraulic structures of the barrages, such as weirs and navigation locks, were also built in this period. Meanwhile, these structures are aged but are still in operation. Thus, they have to be strengthened and repaired, and some of them have to be replaced with new structures. Furthermore, the locks have to be adapted according to the demands of modern inland navigation. Using the example of the double-chamber lock in Aldingen close to Stuttgart, the planning and execution of the overhaul of a concrete lock are described in this paper. The lock was built as part of a barrage on the River Neckar. While the construction of the lock had already started in the 1930s, the structure could not be completed until the end of the 1950s due to the Second World War. The repair of the solid construction is carried out through partial demolition of the chamber walls and the construction of reinforced-concrete facings on the chamber side of the walls.

BLACK SWANS AND RISK - ASSESSING CONSEQUENCES OF EXTREME EVENTS FOR THE GERMAN BIGHT

Westerly and north-westerly storms regularly hit the German North Sea coast causing surges of several meters at the dikes. But extreme events like cyclone Xaver in 2013 are not the largest physically possible events on record. Dangendorf et al. (2016) show that the individual components of the total water level (i.e. mean sea level, surge, and tide) were not at their observed maximum during Xaver. The research project “EXTREMENESS” was initiated to examine the meteorological potential of storms in the German Bight and to assess the consequences of extremely large and rare but physically possible storm surge events, so called “black swans”. Our project partners, the German Meteorological Office, the German Federal Waterways Engineering and Research Institute, and Helmholtz-Zentrum Geesthacht, evaluate possible meteorological and resulting hydraulic boundary conditions including regionally projected sea level rise scenarios which we use to simulate inundations in the study area around Emden (Lower Saxony, Germany) using a two-dimensional hydrodynamic numerical (2D-HN) model. Large parts of the region are situated below mean sea level and drained using tide gates and pumping stations. Therefore the area is highly vulnerable to dike failures and loads exceeding the design levels of defense structures. Combining inundation scenarios with exceeding probabilities and dike failure probabilities will yield risk maps, showing the most vulnerable dike sections and pointing out areas that need particular attention in maintenance.

Dominance of competitors in riparian plant species composition along constructed banks of the German rivers Main and Danube

Hardening of shorelines has been extensively implemented in many parts of the developed world. This also applies to banks of German Federal Waterways, which are mostly fixed by ripraps to prevent bank erosion as a consequence of wave disturbance by shipping traffic. Since ripraps notably alter functions of riparian ecosystems and nature conservation demands recently gained in importance along waterways, alternatives for ripraps play an increasing role.Front-fixed banks are ripraps parallel to the shoreline and embedded in the waterway’s channel with an unsecured bank of low steepness behind them. Thus, they are suitable to prevent banks from erosion. However, it is unclear how they can contribute to the ecological enhancement of riparian vegetation along waterways.Therefore, we compared riparian vegetation of ripraps and front-fixed banks with unsecured banks along the German rivers Main and Danube to assess the ecological efficiency of front-fixed banks. Disturbance by alternating water levels was the lowest at ripraps, whereas disturbance levels were higher at front-fixed and unfortified banks. We used an ordination and indicator species analysis to reveal differences in species composition. The results of the indicator species analysis were analyzed regarding species’ biotope origin, light and moisture demand and life strategy. We analyzed species diversity and calculated functional diversity indices to display the prevalent ecosystem processes.Higher variation in species composition, common indicator species, a strong vertical layering of woody riparian vegetation and similar site conditions at front-fixed and unfortified banks revealed higher similarities in species composition between them than to other bank type combinations. Limnic species occurred with a higher frequency at unfortified and front-fixed banks, whereas terrestrial species were more frequent at ripraps. Light-tolerant species were more common at ripraps, whereas species’ demand for moisture was higher at front-fixed and unfortified banks than at ripraps. Cr-strategists occurred more frequently with increasing disturbance level, whereas c-strategists were more common at ripraps.Ripraps had the highest species diversity levels whereas functional diversity tended to be higher at front-fixed and unfortified banks. This indicates a higher trait complementarity and thus a higher specialization towards alternating water levels, wherefore a higher degree of naturalness can be assumed in these habitats.Nature conservation efforts along German Federal Waterways should focus on the restoration of flooding dynamics, as species typical for riverine habitats are more common at front-fixed and unfortified banks than at ripraps. Since front-fixed banks bear traits suited for the reconnection of rivers and their floodplains and for bank protection, they are a suitable alternative to promote biodiversity along German Federal Waterways.

Bundeswasserstraßenverwaltung und die Umsetzung der Wasserrahmenrichtlinie

Bundeswasserstraßenverwaltung und die Umsetzung der Wasserrahmenrichtlinie

Human impact on plant biodiversity in functional floodplains of heavily modified rivers – A comparative study along German Federal Waterways

Rivers and their floodplains have been strongly influenced by human actions, such as river training measures, flow regulation, bank stabilization, or intensive land use. These alterations threaten the biodiversity of floodplains. While the effects of individual factors on plant species composition and diversity in riparian systems have been frequently studied, it is yet unknown how multiple stressors act in concert and whether the effects remain visible across regions.We chose the floodplains of German Federal Waterways (rivers with a high frequency of shipping traffic) to study the main drivers of plant species composition and biodiversity along heavily modified rivers and aimed to show whether natural differences obscure the effects of human alterations. We recorded the vegetation of river banks, grassland, and alluvial forest fragments in 20 study sites distributed across Germany.Species composition differed from natural floodplain alliances and showed a trend towards terrestrialization and an increase of common species that show no specific preference for floodplain habitats. Despite natural differences such as topography and climate having the strongest influence on plant composition and diversity, the effects of anthropogenic influence (e.g. land use, shipping traffic) remained visible. River construction tended to increase species diversity since the terrestrial species pool is bigger than the one of floodplain specialists. For restoration and ecological river management not only species numbers but their composition and ecological specifics should be considered, and local conditions need to be taken into account.

Geosynthetics for waterways and flood protection structures – Controlling the interaction of water and soil

The interaction of water and soil has been both a blessing and a curse in all times within living memory. Water is the origin of life but is also threatening life when appearing unboundedly. Therefore mankind has always worked hard to benefit from water resources on one hand and to deal with the threat of flooding on the other hand. For both, to protect the land and to allow for beneficial uses like irrigation or navigation, often special measures are necessary to keep the water within certain bounds. Structures to achieve a permanently stable situation like irrigation and navigational canals, river training or flood protection measures need suitable material, carefully thought out design and accurate execution. Often a decision has to be made among competitive approaches to optimize such structures. In many cases, geosynthetics can support or improve the functionality and sometimes only with geosynthetics the desired result can be achieved.Geosynthetics can provide strength and flexibility, imperviousness and drainage, durability and robustness or controlled degradation. All these properties can be of use to handle the many occurrences of interaction of water and soil. Surface water has to be guided or to be kept off; percolating water should be controlled to avoid internal erosion effects should be restrained by appropriate filtration. To guarantee well functioning in general, also chemical and biological aspects have to be considered like ochre formation, root penetration and population by any kind of species. The German Federal Waterways Engineering and Research Institute (BAW) has gathered experience with geosynthetics in hydraulic applications since more than 40 years. These years revealed the capabilities of geosynthetic solutions and simultaneously emphasized the need of careful selection, design and execution.A large variety of geosynthetic fabric and structures is available. To control the interaction of water and soil many different attributes are required, e.g. membranes for impervious lining, filter sheets for erosion control, different kinds of mattresses or wrap-around structures, voluminous elements from sandbags to mega containers for protection, training or immediate repair. In many cases geosynthetics can be designed to control the interaction of water and soil according to the individual and local requirements to allow for an excellent execution of waterways and flood protection structures.

Longitudinal dispersion of radioactive substances in Federal waterways

Abstract In the context of radioactivity monitoring in German Federal Waterways (BWStr) by the Federal Institute of Hydrology (BfG) according to the Precautionary Radiation Protection Act (StrVG), the prediction of the dispersion of radioactive substances in water is one of the key tasks. The aim is the forecasting of the longitudinal dispersion of concentrations of soluble hazardous substances in flowing water. These predictions are based on the so-called dispersion tests with tritium as a tracer that the BfG has performed since 1980. Characteristic parameters like discharge-dependent flow velocities, dispersion and elimination constants related to emission sources or selected river sections are determined. They will serve as basis for a mathematical model to forecast discharge-dependent flow velocities, expected impact times, concentration maxima, and the duration of critical increases in concentrations. In the following, the results obtained till now from three investigation campaigns on the River Weser and its source rivers Werra and Fulda are described.

Prognosis of Methane Formation by River Sediments (9 pp)

Under anoxic conditions typically prevailing in disposal sites for dredged sediment, methanogenesis is the terminal step during microbial degradation of sediment organic matter. Sediment gas production may pose several problems to site management and post-closure utilisation. Depending on the magnitude of gas/methane formation and the intended utilisation of the site, countermeasures will have to be effected during and after deposition of the dredged material. For this purpose it may be of interest to pre-estimate the extent of gas formation from simple sediment variables. Therefore, the aim of the investigations presented here was to analyse the interrelations between gas formation and sediment physical, chemical and biological qualities. Freshly sampled riverbed sediment from nine German federal waterways was analysed for standard solid physical and chemical parameters, pore water composition, cell counts of methanogenic and sulfate-reducing bacteria, and gas formation over a period of 500 days. Particle size and density fractionation were carried out in order to characterise organic matter quality. Correlations between methane formation and sediment chemical, physical and microbiological characteristics were tested using linear and multiple correlation analysis. The selected sediments, including two with marine influence, differed strongly regarding texture, chemical parameters, pore water composition, and methanogen cell counts. The course of methane formation was found to follow distinct phases. The commencement of methane formation was preceded by a lag phase of variable duration. The lag phase was followed by a strong increase of the methane formation rate up to a sediment-characteristic maximum of 5–30 nmol CH4 h–1 g dw–1. Eventually, the rate of methane formation decreased and reached a more stable, long-term level. The extent and amplitude of each phase varied strongly between sediments and could be correlated well with only a few standard analytical parameters, despite the strong heterogeneity of sediment with respect to chemical, physical, and biological characteristics. Lag phase duration depended strongly on the content of inorganic electron acceptors and also on the number of methanogens present at the beginning of the experiment. Maximum and steady state methanogenesis were mainly determined by sediment total nitrogen. As analysis of sediment density fractions revealed that total nitrogen reflected the share of readily degradable macroorganic matter. The results imply that the observed methane formation is a function of the temporally changing balance of the availability of electron acceptors and H2, and the share of easily degradable organic matter. For fresh riverbed sediments, the latter may be deduced from total nitrogen content. Overall, the results showed that methane formation by freshly dredged material may well be pre-estimated from standard analytical data within the first few years of deposition. However, the differently degradable organic matter pools will change over time with respect to size, chemical nature and association with the sediment mineral phase. It can thus be expected that the correlations found in this study will not be readily transferable to older materials. Further studies on the gas formation and organic matter quality by older sediments, e.g. from older dredged material disposal sites of known age, should be conducted and results should be combined with existing organic matter degradation models in order to improve the prediction of sediment gas formation over time.

Monitoring and prediction of the dispersion of radioactive substances in German Federal waterways – concepts and methods

Abstract Based on the Precautionary Radiation Protection Act, the Federal Institute of Hydrology (BfG) is the Federal Center for the monitoring of radioactivity of the German Federal Waterways. In this function, the Institute operates a Radioactivity Measuring and Sampling Network along the Federal Waterways. Priority monitoring tasks are the early warning, the determination of radionuclides in water, suspended solids and sediment (laboratory measurements) and the prediction of dispersion by means of dispersion investigations using tritium as a tracer. This report gives a survey on the present status of the concept and the methods used, as well as an outlook on their further development.