German Federal Institute of Hydrology

Koblenz, Germany

German Federal Institute of Hydrology

Koblenz, Germany
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Westfeld P.,TU Dresden | Maas H.-G.,TU Dresden | Richter K.,TU Dresden | Weiss R.,German Federal Institute of Hydrology
ISPRS Journal of Photogrammetry and Remote Sensing | Year: 2017

This contribution investigates the effects of ocean wave patterns on 3D underwater point coordinate accuracy for LiDAR bathymetry. The refraction of the finite diameter laser pulse passing the air/water interface is modeled differentially in a strict manner. Typical wave patterns and sensor configurations are simulated, and their impact on the 3D coordinates at the bottom of the water body are systematically analyzed. It can be shown that waves have a significant effect on both the planimetry and depth coordinates of underwater topography 3D point cloud coordinates, especially for modern small footprint LiDAR systems. Planimetric effects may reach several decimeters or even meters, and depth coordinate errors also reach several decimeters, even in the case of a horizontal water body bottom. The simulations show that the simplified assumption, that wave effects average out (as is made in most LiDAR bathymetry data processing tools) is not even fulfilled for large footprint systems (spreading the laser beam to a diameter of several meters at the water surface) under certain wave pattern conditions. Modern systems with smaller beam divergence are much more sensitive to wave-induced variations of the refraction conditions and will experience significant wave pattern dependent coordinate errors. The results presented here form a basis for a more strict coordinate correction, if the wave pattern can be modeled from the LiDAR bathymetry water surface reflections or from other observations. Moreover, it will be shown that the induced coordinate errors contain a non-zero bias in addition to a local wave surface dependent quasi-random part, which allows for the formulation of wave pattern dependent correction terms in order to increase the accuracy of LiDAR bathymetry by removing systematic wave pattern dependent effects. © 2017 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)

Wang Z.,Catholic University of Louvain | Hoffmann T.,University of Bonn | Hoffmann T.,German Federal Institute of Hydrology | Six J.,ETH Zurich | And 5 more authors.
Nature Climate Change | Year: 2017

Anthropogenic land cover change (ALCC) is an important carbon (C) loss mechanism, but current methods do not consider the role of accelerated soil organic C erosion and its burial in sediments in their assessments of net soil-atmosphere C exchange. Using a comprehensive global database and parsimonious modelling, we evaluate the impact of anthropogenic soil erosion on C fluxes between the Earth's surface and atmosphere from the onset of agriculture to the present day. We find that agricultural erosion represents a very large and transient perturbation to the C cycle and has induced a cumulative net uptake of 78 ± 22 Pg C in terrestrial ecosystems during the period 6000 BC to AD 2015. This erosion-induced soil organic C sink is estimated to have offset 37 ± 10% of previously recognized C emissions resulting from ALCC. We estimate that rates of C burial have increased by a factor of 4.6 since AD 1850. Thus, current assessments may significantly overestimate both past and future anthropogenic emissions from the land. Given that ALCC is the most uncertain component of the global C budget and that there is a strong connection between ALCC and erosion, an explicit representation of erosion and burial processes is essential to fully understand the impact of human activities on the net soil-atmosphere C exchange. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

Bosshard T.,ETH Zurich | Carambia M.,German Federal Institute of Hydrology | Goergen K.,Center De Recherche Public Gabriel Lippmann | Kotlarski S.,ETH Zurich | And 3 more authors.
Water Resources Research | Year: 2013

The quantification of uncertainties in projections of climate impacts on river streamflow is highly important for climate adaptation purposes. In this study, we present a methodology to separate uncertainties arising from the climate model (CM), the statistical postprocessing (PP) scheme, and the hydrological model (HM). We analyzed ensemble projections of hydrological changes in the Alpine Rhine (Eastern Switzerland) for the near-term and far-term scenario periods 2024-2050 and 2073-2099 with respect to 1964-1990. For the latter scenario period, the model ensemble projects a decrease of daily mean runoff in summer (-32.2%, range [-45.5% to -8.1%]) and an increase in winter (+41.8%, range [+4.8% to +81.7%]). We applied an analysis of variance model combined with a subsampling procedure to assess the importance of different uncertainty sources. The CMs generally are the dominant source in summer and autumn, whereas, in winter and spring, the uncertainties due to the HMs and the statistical PP gain importance and even partly dominate. In addition, results show that the individual uncertainties from the three components are not additive. Rather, the associated interactions among the CM, the statistical PP scheme, and the HM account for about 5%-40% of the total ensemble uncertainty. The results indicate, in distinction to some previous studies, that none of the investigated uncertainty sources are negligible, and some of the uncertainty is not attributable to individual modeling chain components but rather depends upon interactions. ©2012. American Geophysical Union. All Rights Reserved.

Brinke M.,Bielefeld University | Ristau K.,Bielefeld University | Bergtold M.,Bielefeld University | Hoss S.,Ecological Sediment and Soil Assessment | And 3 more authors.
Environmental Toxicology and Chemistry | Year: 2011

The direct and indirect effects of Cd on benthic communities were assessed in a freshwater microcosm study over a period of seven months (218 d). Cadmium was regarded as a model substance to evaluate the usefulness of small-scale laboratory microcosm with microscopic fauna. In particular, effects on the meiofauna community, an ecologically important but rather neglected benthic component, were investigated. In addition, some microfaunal parameters (protozoan abundance and microbial activity) were determined. The sediment was spiked with nominal Cd concentrations of 10, 100, and 1,000 mg/kg dry weight. Because of the strong binding of Cd to sediment particles, measured Cd pore-water concentrations never exceeded 129.5 ± 40.7 μg/L. At 1,000 mg/kg dry weight, the abundances of the two dominant meiofauna taxa, nematodes and oligochaetes, were significantly reduced throughout the present study. Regarding nematodes, species of bacterivorous taxa (Daptonema, Eumonhystera) decreased, whereas species of predacious and omnivorous taxa (Mononchus, Dorylaimus, and Ironus) increased in dominance in microcosms of the highest Cd concentration. Transient effects on microfauna were observed, especially in the first half of the present study, with a reduction in microbial activity and protozoan abundance. However, in microcosms receiving the highest Cd concentration, the abundance of the flagellate Euglena mutabilis increased significantly toward the end of the present study. The results of the present study support the use of small-scale microcosms with natural meiofauna communities as a suitable tool to assess the impact of pollutants in freshwater sediments. © 2010 SETAC.

Kotlarski S.,ETH Zurich | Hagemann S.,Max Planck Institute for Meteorology | Krahe P.,German Federal Institute of Hydrology | Podzun R.,Max Planck Institute for Meteorology | And 2 more authors.
Journal of Hydrology | Year: 2012

The regional climate model REMO extended by the HD river routing scheme (REMO-HD) is applied to the high-impact flooding event of August 2002 in the Elbe river basin. Both the ability of REMO to reproduce the observed precipitation pattern and the ability of the HD Model to translate the grid cell based runoff provided by REMO into streamflow are assessed. REMO-HD is operated with different settings and with different initialization fields but is always driven by the ECMWF operational analysis. The combined model system, operating at a spatial resolution of 18. km, is able to approximately capture the basic spatio-temporal patterns of precipitation and of river discharge during this particular event. Peak precipitation, however, is systematically underestimated. In detail, the performance depends on the specific configuration of the model system. In its optimal setup, REMO-HD is able to reproduce the timing and the magnitude of the flood peak at several gauging stations along the Elbe river despite the fact that the HD routing scheme was not explicitly calibrated for the catchment. A frequent re-initialization of REMO's atmospheric fields (forecast mode) slightly improves the simulation of precipitation but can also lead to local inaccuracies. The initialization procedure for soil moisture in the climate model is identified as a key element exerting a primary control on the simulated amounts of grid cell runoff and, consequently, on the simulated river discharge. The soil moisture initialization has only a limited influence on the simulated precipitation pattern. This indicates that the precipitation event has been primarily synoptically driven and that regional-scale land-atmosphere interactions involving evapotranspiration have been of no or only of minor importance. The results obtained increase our confidence in the potential of regional climate models extended by river routing schemes to be applied also for hydrological climate impact studies involving the analysis of extreme events. © 2012 Elsevier B.V..

Hagerbaumer A.,Bielefeld University | Hoss S.,Ecossa | Heininger P.,German Federal Institute of Hydrology | Traunspurger W.,Bielefeld University
Journal of Nematology | Year: 2015

With respect to their high abundances, their role as intermediaries between microorganisms and higher trophic levels, and their ubiquitous occurrence in all habitats, nematodes are of strong potential interest as environmental indicators. Ecotoxicological methods to evaluate the risk of anthropogenic pollutants on ecosystems require both in vitro and in vivo toxicity tests to investigate either mechanisms or pathways of toxicity and to set accurate toxicity thresholds. For this, the interest in nematodes as model organisms in ecotoxicology increased over the past few decades and existing appropriate experimental methods are reviewed in this manuscript. An overview of the various existing ecotoxicological tools for nematodes, ranging from molecular laboratory methods to experimental model ecosystem approaches, and their role as indicator organisms is given. The reviewed studies, approaches that range from species-based to community-based methods, reveal exciting possibilities for the future use of nematodes in ecotoxicological studies. Suitable ecotoxicological tools and ecological indices for nematodes should be integrated in weight-of-evidence approaches for assessing the ecological risk of contamination. © The Society of Nematologists 2015.

Kathol M.,University of Cologne | Fischer H.,German Federal Institute of Hydrology | Weitere M.,University of Cologne | Weitere M.,Helmholtz Center for Environmental Research
Freshwater Biology | Year: 2011

1.Over the course of this 17-month study, we assessed the potential loss of plankton (bacteria, algae, heterotrophic flagellates) to consumers (ciliates and rotifers) within mature biofilms established on natural substrata exposed to the main current of the River Rhine (Germany). Once a month, in flow cells in a bypass system to the River Rhine, we measured the clearance rates of the biofilm-associated consumers on the different groups within the natural plankton. 2.Ciliates were the most dominant consumers, among which planktivorous groups, particularly peritrichs and (in spring and summer) heterotrichs dominated. Consumer biomass varied with season, with the highest density occurring directly after the appearance of the phytoplankton spring peak. 3.Clearance rates on plankton ranged from 96 to 565Lm-2d-1 for bacteria and 66-749Lm-2d-1 for algae, with a preference for algae in summer and for bacteria in winter. This pattern coincided with seasonal changes in the structures of the grazer communities. The consumers (both ciliates and rotifers with total standing stocks ranging between 19 and 572mgCm-2) imported a substantial amount of organic matter (between 15 and 137mgCm-2d-1) into the biofilm. 4.These results highlight the potential importance of consumers in the biofilm as a trophic link between the plankton and the benthos, a function that has hitherto mostly been attributed to filter-feeding bivalves. In contrast to bivalves, the biofilm-dwelling consumers show a more dynamic response towards the plankton density and composition. Such dynamic components need to be considered when estimating total plankton consumption by the benthos. © 2011 Blackwell Publishing Ltd.

Benjankar R.,University of Idaho | Koenig F.,German Federal Institute of Hydrology | Tonina D.,University of Idaho
Journal of Hydrology | Year: 2013

Recent national and international legislation (e.g., the European Water Framework Directive) identified the need to quantify the ecological condition of river systems as a critical component for an integrated river management approach. An important defining driver of ecological condition is stream hydromorphology. Several methodologies have been proposed from simple table-based approaches to complex hydraulics-based models. In this paper, three different methods for river hydromorphological assessment are applied to the Boise River, United States of America (USA): (1) the German LAWA overview method (Bund/Laender Arbeitsgemeinschaft Wasser/German Working Group on water issues of the Federal States and the Federal Government represented by the Federal Environment Ministry), (2) a special approach for a hydromorphological assessment of urban rivers and (3) a hydraulic-based method. The hydraulic-based method assessed stream conditions from a statistical analysis of flow properties predicted with hydrodynamic modeling. The investigation focuses on comparing the three methods and defining the transferability of the methods among different contexts, Europe and West United States. It also provides comparison of the hydromorphological conditions of an urban and a rural reaches of the Boise River. © 2013 Elsevier B.V.

Buchinger S.,German Federal Institute of Hydrology | Spira D.,German Federal Institute of Hydrology | Broder K.,German Federal Institute of Hydrology | Schlusener M.,German Federal Institute of Hydrology | And 2 more authors.
Analytical Chemistry | Year: 2013

The present study investigated the hypothesis that the coupling of high-performance thin-layer chromatography with the yeast estrogen screen (planar-YES, p-YES) can be used as a screening tool for effect-directed analysis. Therefore, the proposed method was challenged for the first time with several real samples from various origins such as sediment pore water, wastewater, and sunscreens. It was possible to detect and quantify estrogenic effects in all investigated sample types, even in the presence of demanding matrixes. Furthermore, the specific agonistic effect of the estrogen receptor activation could be detected in samples exhibiting cytotoxic effects and at cytotoxic levels of analyzed estrogenic compounds, which is not possible with the classic YES. The analysis of samples by the p-YES results in profiles of estrogenic activity. By means of this profiles samples can be compared qualitatively and quantitatively with respect to different compositions of bioactive compounds in mixtures. In conclusion, the p-YES approach seems to have a high potential to be used as a valuable screening tool for various applications in effect-directed analysis. © 2013 American Chemical Society.

Hemri S.,Heidelberg Institute for Theoretical Studies | Lisniak D.,German Federal Institute of Hydrology | Klein B.,German Federal Institute of Hydrology
Water Resources Research | Year: 2015

Hydrologic ensemble forecasts driven by atmospheric ensemble prediction systems need statistical postprocessing in order to account for systematic errors in terms of both location and spread. Runoff is an inherently multivariate process with typical events lasting from hours in case of floods to weeks or even months in case of droughts. This calls for multivariate postprocessing techniques that yield well-calibrated forecasts in univariate terms and ensure a realistic temporal dependence structure at the same time. To this end, the univariate ensemble model output statistics (EMOS) postprocessing method is combined with two different copula approaches that ensure multivariate calibration throughout the entire forecast horizon. The domain of this study covers three subcatchments of the river Rhine that represent different sizes and hydrological regimes: the Upper Rhine up to the gauge Maxau, the river Moselle up to the gauge Trier, and the river Lahn up to the gauge Kalkofen. In this study, the two approaches to model the temporal dependence structure are ensemble copula coupling (ECC), which preserves the dependence structure of the raw ensemble, and a Gaussian copula approach (GCA), which estimates the temporal correlations from training observations. The results indicate that both methods are suitable for modeling the temporal dependencies of probabilistic hydrologic forecasts. © 2015. American Geophysical Union. All Rights Reserved.

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