Surrogate-Enhanced Parameter Inference for Function-Valued Models

We present an approach to enhance the performance and flexibility of the Bayesian inference of model parameters based on observations of the measured data. Going beyond the usual surrogate-enhanced Monte-Carlo or optimization methods that focus on a scalar loss, we place emphasis on a function-valued output of a formally infinite dimension. For this purpose, the surrogate models are built on a combination of linear dimensionality reduction in an adaptive basis of principal components and Gaussian process regression for the map between reduced feature spaces. Since the decoded surrogate provides the full model output rather than only the loss, it is re-usable for multiple calibration measurements as well as different loss metrics and, consequently, allows for flexible marginalization over such quantities and applications to Bayesian hierarchical models. We evaluate the method’s performance based on a case study of a toy model and a simple riverine diatom model for the Elbe river. As input data, this model uses six tunable scalar parameters as well as silica concentrations in the upper reach of the river together with the continuous time-series of temperature, radiation, and river discharge over a specific year. The output consists of continuous time-series data that are calibrated against corresponding measurements from the Geesthacht Weir station at the Elbe river. For this study, only two scalar inputs were considered together with a function-valued output and compared to an existing model calibration using direct simulation runs without a surrogate.

Microplastic in Water and Sediments at the Confluence of the Elbe and Mulde Rivers in Germany

Accumulation of microplastics in aquatic environments is an issue of emerging concern. Initially, research focused on marine systems. However, recent studies also investigate the abundance of microplastics in freshwater environments. Rivers connect terrestrial with marine ecosystems and contribute a considerable share of macro- and microplastics to the oceans. A previous study found a large amount of micro-spheres in Dessau downstream the river mouth of the Mulde. Therefore, the objective of this research was to examine whether the Mulde river with its highly industrialized catchment contributes to the microplastic pollution of the Elbe. Sediment (Van Veen grab sampler) and water samples (filter cascade with the smallest mesh size 50 μm and nets with the smallest mesh size 150 μm) were taken from the Elbe river up- and downstream the confluence with the Mulde. After extensive sample preparation, we examined the samples under a digital microscope and determined polymer types by pyrolysis Gas Chromatography/Mass Spectrometry (pyr-GC-MS). The amount of primary microplastics increased in sediment and water samples just downstream the confluence. Those microplastics originate probably from the Mulde. We measured larger amounts and different shapes of microplastics in filter cascades that have a smaller mesh size compared to the nets.

Storm surge development in the Southern North Sea and the Elbe river in Europe during the last century and its practical application

ABSTRACT. The development of storm surges during the last century in the European North Sea and the Elbe River is presented. The results show an increase in the number of the storm tides and the storm surge curves, but no increase in the level. The reason for the increase of the storm surge curves - especially those with more than one storm tide crest - must be an increase of the wind duration. With the analyses of the storm surge curve and the storm surge peak, it is possible to calculate the design dike level.

Historical River Training Works on the Lower Elbe

The paper deals with river training works built on the reach of the Elbe River between the city of Ústí nad Labem (CZ) and the Czech/German border. Downstream of the Ústí nad Labem, the Elbe in the Czech Republic and in Germany has only been made navigable through river training measures without building weirs. The goal of river training for watercourse navigability is to attain the required waterway parameters through fairway adjustments. This is primarily achieved through channel dredging and the construction of training dams to concentrate the water flow into a narrower but deeper main channel. The paper describes the historical development of river training works during the period from the Middle Ages to the present day. Initially, such works were not meant as part of a unified conceptually designed system of measures. Instead, they were local initiatives aimed to remove natural obstacles from the river bed and to build facilities and structures to aid navigation. Systematic regulation works along the Czech and German sections of the Elbe only started in the early 19th century. The research was focused on studying the original project documents and documentation of the actual design of the training dams since 1894. This historical design documentation was digitised and projected into the maps in the Czech JTSK local coordinate system through the use of advanced geographic information system (GIS) methods. The final atlas of river training works on the Elbe-Vltava Waterway (EVW) along the lower Elbe in the Czech Republic is the first of its kind, utilising geographic information systems to document the locations of technical structures built since the early 19th century in the Elbe River bed in order to make the river navigable and maintain its navigability. The collection of maps also documents the development of the river training works in time based on map data obtained from digitised design documentation from the 19th and 20th centuries, historical aerial photographs dated 1930–1946 and 1950–1964, and present-day maps and orthophotomaps of the Elbe section in question. The atlas of the Elbe-Vltava Waterway river training works is publicly available via a web-based application. The maps are a result of original research and offer a synthesis of interactions between the existing technical structures, the sediment regime of the Elbe and sites that are subject to environmental protection. The research was conducted as part of project no. DG18P02OVV004 entitled “Documentation and presentation of technical cultural heritage along the Elbe-Vltava Waterway” within a support programme for applied research and experimental development of national and cultural identity, funded by the Ministry of Culture of the Czech Republic.

Management of Global Warming Effects in the European Water Framework Directive: Consideration of Social–Ecological System Features in the Elbe River Basin District

In this study, we examined the extent to which global warming management is currently integrated into the European Water Framework Directive (WFD), the central legal framework for water management in the EU. We focused on the Elbe River Basin District and how global warming is addressed in its water management. We used the social–ecological systems (SES) approach as our theoretical framework, representing an eminent analytical frame of biosphere-based sustainability science. In our study, we analysed core characteristics of SES in the context of global warming to evaluate the effectiveness of current water management in the Elbe River basin concerning long-term changing climate conditions. To determine to what extent each SES feature is considered in the Elbe water management, we applied a scale of 1 to 5. Our results show that the SES feature “scale and openness” is best addressed (score 4.0) by the Elbe River basin management, followed by “context dependency” (score 3.9); however, “non-linearity, uncertainty, unpredictability” (score 3.2), “self-organisation and adaptability” (score 3.1), and “dynamics” (score 3.0) have only moderate impacts. SES features can only be considered comprehensively if global warming is accounted for in an integrated way at a European level. In order to ensure effective implementation, explicit regulations and legally binding obligations are most likely required.

Anthropogenic Transformation Disconnects a Lowland River From Contemporary Carbon Stores in Its Catchment

Rivers transport carbon from continents to oceans. Surprisingly, this carbon has often been found to be centuries old, not originating from contemporary plant biomass. This can be explained by anthropogenic disturbance of soils or discharge of radiocarbon–depleted wastewater. However, land enclosure and channel bypassing transformed many rivers from anabranching networks to single–channel systems with overbank sediment accumulation and lowered floodplain groundwater tables. We hypothesized that human development changed the fluvial carbon towards older sources by changing the morphology of watercourses. We studied radiocarbon in the Elbe, a European, anthropogenically–transformed lowland river at discharges between low flow and record peak flow. We found that the inorganic carbon, dissolved organic carbon (DOC) and particulate organic carbon was aged and up to 1850 years old. The ∆14C values remained low and invariant up to median discharges, indicating that the sources of modern carbon (fixed after 1950) were disconnected from the river during half of the time. The total share of modern carbon in DOC export was marginal (0.04%), 72% of exported DOC was older than 400 years. This was in contrast to undisturbed forested subcatchments, 72% of whose exported DOC was modern. Although population density is high, mass balances showed that wastewater did not significantly affect the ∆14C-DOC in the Elbe river. We conclude that wetlands and other sources of contemporary carbon were decoupled from the anthropogenically transformed Elbe stream network with incised stream bed relative to overbank sediments, shifting the sources of fluvial carbon in favor of aged stores.

Parameter Dependences Arising from Calibration of a Riverine Diatom Model - Representation in Terms of Posterior Conditional Distributions

We address the analysis and proper representation of posterior dependence among parameters obtained from model calibration. A simple water quality model for the Elbe River (Germany) is referred to as an example. The joint posterior distribution of six model parameters is estimated by Markov Chain Monte Carlo sampling based on a quadratic likelihood function. The estimated distribution shows to which extent model parameters are controlled by observations, highlighting issues that cannot be settled unless more information becomes available. In our example, some vagueness occurs due to problems in distinguishing between the effects of either growth limitation by lack of silica or a temperature dependent algal loss rate. Knowing such indefiniteness of the model structure is crucial when the model is to be used in support of management options. Bayesian network technology can be employed to convey this information in a transparent way.

Residues of selected sulfonamides, non-steroidal anti-inflammatory drugs and analgesics-antipyretics in surface water of the Elbe river basin (Czech Republic)

The occurrence of human as well as veterinary drug residues in surface water is caused by their insufficient removal ability from wastewater. Drug residues disturb the natural balance of water ecosystem, have a negative effect on non-target organisms and pose a significant risk for human health. The main aim of this study was to determine the concentration of residues of eight drugs from the group of sulfonamides (sulfathiazole, sulfadiazine, sulfamethazine, sulfamethoxazole, sulfadimethoxine, sulfadoxine, sulfamerazine, sulfachlorpyridazine), four drugs from the non-steroidal anti-inflammatory drug group (ibuprofen, ketoprofen, naproxen, diclofenac) and one representative of the analgesics-antipyretics group [paracetamol (acetaminophen)] in the surface water of the Elbe river basin. A total of 65 samples of surface water from the Elbe river basin were taken during August 2018 when the weather was constant without any significant fluctuations. The analysis was performed by means of liquid chromatography with tandem mass spectrometry (LC-MS/MS). The results have shown the numerous occurrences of sulfamethoxazole, ibuprofen, naproxen, diclofenac and paracetamol (acetaminophen). A statistically significant negative correlation between the river flow rate in the monitored locations and the residue concentration was found for ibuprofen, naproxen, diclofenac and paracetamol (acetaminophen). The most significant findings of the monitored drug residues were mostly determined in samples from small streams below larger urban settlements with a hospital or other health facilities.

Mycoplankton Biome Structure and Assemblage Processes Differ Along a Transect From the Elbe River Down to the River Plume and the Adjacent Marine Waters

Rivers are transport systems and supply adjacent ecosystems with nutrients. They also serve human well-being, for example as a source of food. Microorganism biodiversity is an important parameter for the ecological balance of river ecosystems. Despite the knowledge that fungi are key players in freshwater nutrient cycling and food webs, data on planktonic fungi of streams with higher stream order are scarce. This study aims to fill this knowledge gap by a fungi-specific 18S ribosomal RNA (rRNA) gene tag sequencing approach, investigating mycoplankton diversity in the Elbe River along a transect from shallow freshwater, to the estuary and river plume down to the adjacent marine waters (sections of seventh stream order number). Using multivariate analyses and the quantitative process estimates (QPEs) method, questions (i) of how mycoplankton communities as part of the river continuum change along the transect, (ii) what factors, spatial and environmental, play a role, and (iii) what assembly processes, such as selection or dispersion, operate along the transect, were addressed. The partitioning of mycoplankton communities into three significant distant biomes was mainly driven by local environmental conditions that were partly under spatial control. The assembly processes underlying the biomes also differed significantly. Thus, variable selection dominated the upstream sections, while undominated processes like ecological drift dominated the sections close to the river mouth and beyond. Dispersal played a minor role. The results suggest that the ecological versatility of the mycoplankton communities changes along the transect as response, for example, to a drastic change from an autotrophic to a heterotrophic system caused by an abrupt increase in the river depth. Furthermore, a significant salinity-dependent occurrence of diverse basal fungal groups was observed, with no clade found exclusively in marine waters. These results provide an important framework to help understand patterns of riverine mycoplankton communities and serve as basis for a further in-depth work so that fungi, as an important ecological organism group, can be integrated into models of, e.g., usage-balance considerations of rivers.