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Richter K.,TU Dresden | Maas H.-G.,TU Dresden | Westfeld P.,TU Dresden | Weiss R.,Bundesanstalt fur Gewasserkunde
Photogrammetrie, Fernerkundung, Geoinformation | Year: 2017

Airborne lidar bathymetry is an efficient technique for measuring the bottom of shallow water bodies. A characteristical feature of lidar bathymetry beam propagation is given by scattering and absorption effects in the water column, both leading to a loss of received signal intensity. This loss of signal intensity depends on the turbidity of the water body. Inversely, an analysis of the decay of the recorded waveform signal allows for deriving statements on the local degree of turbidity in the water. The paper shows a first approach on the determination of one turbidity measure per laser pulse by analysing the recorded waveform and fitting an exponential function, wherein the decay coefficient depicts an integral measure describing turbidity. The technique was applied to a shallow inland water, and the results were validated by conventional point-wise turbidity measurement techniques. An obvious consequence of attenuation and loss of signal intensity in lidar bathymetry is the fact that the bottom returns become rather weak. In many cases, conventional ground pulse echo detection techniques fail in detecting water bottom points, leading to a reduced number of water body bottom points and thus limiting the application range of the technique. To partly compensate for this effect, a differential backscatter cross section determination based signal attenuation correction method has been developed, which allows for a signal-derived re-amplification of the ground signal. Although the technique also amplifies noise, it could be shown that it is capable of delivering a higher number of additional ground points and thus extending the applicability of the technique. © 2017 Deutsche Gesellschaft für Photogrammetrie, Fernerkundung und Geoinformation (DGPF) e.V.

Rossa A.,ARPAV | Liechti K.,Swiss Federal Institute of forest | Zappa M.,Swiss Federal Institute of forest | Bruen M.,University College Dublin | And 5 more authors.
Atmospheric Research | Year: 2011

Quantifying uncertainty in flood forecasting is a difficult task, given the multiple and strongly non-linear model components involved in such a system. Much effort has been and is being invested in the quest of dealing with uncertain precipitation observations and forecasts and the propagation of such uncertainties through hydrological and hydraulic models predicting river discharges and risk for inundation. The COST 731 Action is one of these and constitutes a European initiative which deals with the quantification of forecast uncertainty in hydro-meteorological forecast systems. COST 731 addresses three major lines of development: (1) combining meteorological and hydrological models to form a forecast chain, (2) propagating uncertainty information through this chain and make it available to end users in a suitable form, (3) advancing high-resolution numerical weather prediction precipitation forecasts by using non-conventional observations from, for instance, radar to determine details in the initial conditions on scales smaller than what can be resolved by conventional observing systems. Recognizing the interdisciplinarity of the challenge COST 731 has organized its work forming Working Groups at the interfaces between the different scientific disciplines involved, i.e. between observation and atmospheric (and hydrological) modelling (WG-1), between atmospheric and hydrologic modelling (WG-2) and between hydrologic modelling and end-users (WG-3).This paper summarizes the COST 731 activities and its context, provides a review of the recent progress made in dealing with uncertainties in flood forecasting, and sets the scene for the papers of this Thematic Issue. In particular, a bibliometric analysis highlights the strong recent increase in addressing the uncertainty analysis in flood forecasting from an integrated perspective. Such a perspective necessarily involves the area of meteorology, hydrology, and decision making in order to take operational advantage of the scientific progress, an aspect in which COST 731 is successfully contributing to furthering the flood damage mitigation capabilities in Europe. © 2010 Elsevier B.V.

PubMed | University of Aalborg, Bundesanstalt fur Gewasserkunde, Technical University of Denmark, Kruger A S and San Luis Potosí Institute of Scientific Research and Technology
Type: | Journal: Water research | Year: 2016

Organic micropollutants (OMPs) such as pharmaceuticals are persistent pollutants that are only partially degraded in waste water treatment plants (WWTPs). In this study, a membrane bioreactor (MBR) system was used as a polishing step on a full-scale WWTP, and its ability to remove micropollutants was examined together with the development and stability of the microbial community. Two stages of operation were studied during a period of 9 months, one with (S1) and one without (S2) the addition of exogenous OMPs. Ibuprofen and naproxen had the highest degradation rates with values of 248g/g

Wetzel M.A.,Bundesanstalt fur Gewasserkunde | Wiegmann M.,Wasser und Schifffahrtsamt Cuxhaven | Koop J.H.E.,Bundesanstalt fur Gewasserkunde
Geotextiles and Geomembranes | Year: 2011

Geotextile materials find increasing use in coastal protection as an alternative material to natural stone, slag, and concrete. In this environment geotextiles, like all surfaces of technical objects immersed in seawater, are subject to accumulation of organisms on their surfaces, a process usually called biofouling. In a 2-year experiment we investigated the colonization of benthic organisms on two different geotextile materials (woven fabric and non-woven fabric) in the Elbe estuary, Germany, and compared it with the colonization on unglazed ceramic tiles as reference representing the nearest compromise to natural hard substrates. Then, non-woven fabric was colonized by significantly less species, fewer individuals, and lower biomass values than the woven fabric and the ceramic tiles (one-factor ANOVA, p< 0.05); no such significant differences were noted between woven fabric and ceramic tiles. Over time, the numbers of species and numbers of individuals did not show significant increases between the first and the second year (Student's t-test, p≥ 0.05), while the biomass was still increasing significantly on all materials (t-test, p< 0.05). However, biomass was almost two orders of magnitude lower on non-woven geotextiles than on woven material. Exposure to seawater and fouling organisms had no adverse effect upon the stability of the geotextiles (wide-width tensile test results; t-test p≥ 0.05). Geotextile materials therefore offer a unique choice in coastal and hydraulic engineering: depending on the application, engineers can choose between a material that is easily colonized by benthic species, or one that minimizes such colonization where it is undesired. © 2010 Elsevier Ltd.

Reggiani P.,Deltares | Reggiani P.,RWTH Aachen | Todini E.,University of Bologna | Meissner D.,Bundesanstalt fur Gewasserkunde
Hydrology Research | Year: 2014

The kinematic wave approach is often used in hydrological models to describe channel and overland flow. The kinematic wave is suitable for situations where the local and convective acceleration, as well as the pressure term in the dynamic wave model is negligible with respect to the friction and body forces. This is the case when describing runoff processes in the upper parts of catchments, where slopes are generally of the order of 10-3. In physical-based hydrological models, the point-scale conservation equations are integrated over model entities, such as grid pixels or control volumes. The integration leads to a set of ordinary differential governing equations, which can be solved numerically by methods such as the Runge-Kutta integrator. Here, we propose an analytical solution of a Taylor-series approximation of the kinematic wave equation, which is presented as nonlinear reservoir equation. We show that the analytical solution is numerically robust and third-order accurate. It is compared with the numerical solution and the solution of the complete dynamic wave model. The analytical solution proves to be computationally better performing and more accurate than the numerical solution. The proposed analytical solution can also be generalized to situations of leaking channels. © IWA Publishing 2014.

Hijosa-Valsero M.,University of León | Fink G.,Bundesanstalt fur Gewasserkunde | Schlusener M.P.,Bundesanstalt fur Gewasserkunde | Sidrach-Cardona R.,University of León | And 3 more authors.
Chemosphere | Year: 2011

Seven mesocosm-scale constructed wetlands (CWs), differing in their design characteristics, were set up in the open air to assess their efficiency to remove antibiotics from urban raw wastewater. A conventional wastewater treatment plant (WWTP) was simultaneously monitored. The experiment took place in autumn. An analytical methodology including HPLC-MS/MS was developed to measure antibiotic concentrations in the soluble water fraction, in the suspended solids fraction and in the WWTP sludge. Considering the soluble water fraction, the only easily eliminated antibiotics in the WWTP were doxycycline (61. ±. 38%) and sulfamethoxazole (60. ±. 26%). All the studied types of CWs were efficient for the removal of sulfamethoxazole (59. ±. 30-87. ±. 41%), as found in the WWTP, and, in addition, they removed trimethoprim (65. ±. 21-96. ±. 29%). The elimination of other antibiotics in CWs was limited by the specific system-configuration: amoxicillin (45. ±. 15%) was only eliminated by a free-water (FW) subsurface flow (SSF) CW planted with Typha angustifolia; doxycycline was removed in FW systems planted with T. angustifolia (65. ±. 34-75. ±. 40%), in a Phragmites australis-floating macrophytes system (62. ±. 31%) and in conventional horizontal SSF-systems (71. ±. 39%); clarithromycin was partially eliminated by an unplanted FW-SSF system (50. ±. 18%); erythromycin could only be removed by a P. australis-horizontal SSF system (64. ±. 30%); and ampicillin was eliminated by a T. angustifolia-floating macrophytes system (29. ±. 4%). Lincomycin was not removed by any of the systems (WWTP or CWs). The presence or absence of plants, the vegetal species (T. angustifolia or P. australis), the flow type and the CW design characteristics regulated the specific removal mechanisms. Therefore, CWs are not an overall solution to remove antibiotics from urban wastewater during cold seasons. However, more studies are needed to assess their ability in warmer periods and to determine the behaviour of full-scale systems. © 2011 Elsevier Ltd.

Decision making in landscape planning needs a procedure for the easy rating of the habiat quality of riparian floodplains. Based on the difference of the mean high-water level (W-MHQ) minus the mean water level (W-MQ) and the intersection with terrain level of whitewillow stands, an indicator was created. This value allows direct inference of the potential site quality of the floodplain.The method is intended for use on floodplains of big rivers used as navigable waterways. The approach is general, and is thus also applicable at floodplains of other big rivers. This method makes it possible to evaluate the Influence of man-made changes of the water level on riparian terrestrical habitats.

Within the scope of a comprehensive international study about the flow regime in the Rhine basin it was found that a clearly detectable dynamism of change has acted here in the course of the 20th century that has even gained in intensity in last few decades. In the course of that, seasonal re-arrangements of runoff have manifested themselves preferrentially in the Alpine region and in the basins of the High Rhine and the Upper Rhine. In the northern part of the Rhine basin, downstream of the inflow of the River Main, primarily winter runoff has increased. Thus, characteristic signals of the climate-change impacts have begun to show in Central Europe already in the hydrological developments of the last 100 years, although it is hardly possible to distinguish this climatic impact from anthropogenic change-inducing causes, such as building and operation of storage reservoirs or impoundments.

Siebeneicher S.,TU Dresden | Wahrendorf D.-S.,Bundesanstalt fur Gewasserkunde | Wetzel M.A.,Bundesanstalt fur Gewasserkunde | Jungmann D.,TU Dresden
Journal of Soils and Sediments | Year: 2013

Purpose: Acute whole-sediment bioassay with the estuarine and marine amphipod Corophium volutator (Pallas) is widely used to assess toxicity of sediments. According to the guidelines DIN EN ISO 16712, mortality is the determined toxic endpoint. Additionally, the reburrowing ability of the surviving organisms of this acute toxicity test in fresh uncontaminated sediment is suggested as the sublethal endpoint, but insufficient information (e. g., exact measurement protocols) on this endpoint is provided, thus confounding factors and the interpretation of the results. The aim of this study was to provide information on burrowing activity as a sublethal endpoint. Materials and methods: Amphipod tests were carried out in the laboratory, and the burrowing behavior was examined in a size- and gender-specific manner. For sediment testing, only animals of the same size were used in a defined sex ratio because it was found that female animals buried themselves faster than males and that smaller animals burrowed faster than bigger organisms. Statistical analyses were applied to determine whether burrowing time and ability differ significantly between sexes and sizes. Finally, tests were run to discern whether the burrowing ability could be a more sensitive endpoint than mortality. Results and discussion: When the burrowing ability was examined in toxicity tests with contaminated sediment, the test organisms were affected in a dose-dependent manner. With rising concentrations of the contaminated sediment in a sublethal testing following the sediment exposure over 10 days, fewer animals buried themselves into the sediment. Conclusions: The burrowing behavior can be used as an additional endpoint. For the tested sediment, burrowing was found to be more sensitive than the mortality. Guidance on the measurement protocol for this additional endpoint was developed. Under the test conditions examined, burrowing ability is an appropriate sublethal endpoint to supplement the toxicity test procedure. © 2012 Springer-Verlag Berlin Heidelberg.

Dickscheid T.,Bundesanstalt Fur Gewasserkunde | Forstner W.,University of Bonn
Photogrammetrie, Fernerkundung, Geoinformation | Year: 2013

Many vision applications rely on local features for image analysis, notably in the areas of object recognition, image registration and camera calibration. One important example in photogrammetry are fully automatic algorithms for relative image orientation. Such applications rely on a matching algorithm to extract a sufficient number of correct feature correspondences at acceptable outlier rates, which is most often based on the similarity of feature descriptions. When the number of detected features is low, it is advisable to use multiple feature detectors with complementary properties. When feature similarity is not sufficient for matching, spatial feature relationships provide valuable information. In this work, a highly generic matching algorithm is proposed which is based on a trainable Markov random field (MRF). It is able to incorporate almost arbitrary combinations of features, similarity measures and pairwise spatial relationships, and has a clear statistical interpretation. A major novelty is its ability to compensate for weaknesses in one information cue by implicitely exploiting the strengths of others. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.

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