1,721,203 research outputs found
Sturzfluten in kleinen Einzugsgebieten: Relevante Prozesse, Muster und Strategien für eine verbesserte Modellierung in der Bemessungspraxis
Get PDFMapping the surface water storage variation in densely impounded semi-arid NE Brazil with satellite remote sensing approach
Get PDFSurface water bodies provide vital support to the society and fundamentally affect ecosystems in various manners. Precise knowledge of the spatial extent of surface water bodies (e.g. reservoirs) as well as of the quantity of water they store is necessary for efficient water deployment and understanding of the local hydrology. Remote sensing provides broad opportunities for surface water mapping. The main objectives of this thesis are: 1) delineating surface water area of partly vegetated water bodies only from remote sensing data without field data input; 2) obtaining the surface water storage, and 3) analyzing its spatio-temporal variations for northeastern (NE) Brazil as a representative for a densely dammed semi-arid region.
At first, I investigated the potential of digital elevation models (DEMs) generated from TanDEM-X data, which were acquired during the low water level stage, for reservoirs’ bathymetry derivation. I found that the accuracy of such DEMs can reach one meter, both in the absolute and relative respects. It has shown that DEMs derived from TanDEM-X data have great potentials for representing the reservoirs’ bathymetry of temporally dried-out reservoirs.
Subsequently, I targeted at developing a method for mapping the water surface beneath canopy independent of field data for further delineation of the effective water surface. Instead of the commonly used backscattering coefficients, I investigated the capability of the Gray-Level Co-Occurrence Matrix (GLCM) texture index to distinguish different types of Radar backscattering taking place in (partly) vegetated reservoirs. This experiment demonstrated that different types of backscattering at the vegetated water surface show distinct statistical characteristics on GLCM variance derived from TerraSAR-X satellite time series data. Furthermore, with the threshold established based on the statistics of the sub-populations dominated by different types of backscattering, the vegetated water surfaces were effectively mapped, and the effective water surface areas were further delineated with an accuracy of 77% to 95%.
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Based on the investigation of the DEMs generated from TanDEM-X data, I derived the formerly unknown bathymetry for 2 105 reservoirs of various sizes in four representative regions of an overall area of 10 000 km2. The spatial distributions of surface water storage capacities in the four regions were subsequently extracted from the combination of the reservoir bathymetry and the water surface extents provided by RapidEye satellite time series. Furthermore, the spatio-temporal variations of surface water storage were derived for the four representative regions on an annual basis in the period of 2009-2017. This study showed that 1) The density of reservoirs in NE Brazil amounts to 0.04-0.23 reservoirs per km2, the corresponding water surface and surface water storage are 1.18-4.13 ha/km2 and 0.01-0.04 hm3 m/km², respectively; 2) On the spatial unit of 5×5 km2, the surface water storage in the region constantly decreased due to a prolonged drought with a rate of 105 m3/year from 2009 to 2017, with a slight increase from 2016 to 2017 in a few reservoirs; 3) Local precipitation deficit controls the variation of the overall surface water storage in the region. In this thesis I demonstrated the great potential of the great potential of SAR and optical satellite time series data for hydrological applications. The method I developed for delineating the effective water extent from the vegetated reservoirs has shown high potential transferability for other similar regions. The data gaps of bathymetry and surface waters storage capacity were filled for 2 105 reservoirs in NE Brazil. The results of the spatio-temporal variations of surface water storage in four representative regions from 2009-2016 can support future water management and improve hydrological prediction in NE Brazil
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Umgehung der Probleme bei der numerischen Lösung der Richards-Gleichung durch Anwendung der Fuzzy-Logik
No full textHydrologische Modellierung urbaner Nährstoffeinträge in Gewässer auf Flussgebietsebene
Get PDFThis thesis describes the conception and implementation of the hydrological model ArcEGMO-URBAN and its application to the basin of the Havel river in north-eastern Germany. The model has been developed in order to make up the balance of nitrogen and phosphorus inputs from point sources in urban areas on the scale of river basins. The nutrient input can be calculated with a high spatial resolution and according to its seasonal variation. At the same time, the impact of the rainfall on the nutrient input is being focused on in this project...thesi
Simulation von Wassermangelsituationen im Nordostdeutschen Tiefland mittels gekoppelter Oberflächen- und Grundwassermodelle
Get PDFDie Modellierung aller auf der gesamten Einzugsgebietsebene relevanten Abflussbil-dungsprozesse ist unter aktuellen Fragestellungen unumgänglich. Ziel dieser Arbeit ist die quantitative Analyse und Abbildung der Wechselwirkungen zwischen Oberflächen- und Grundwasser mit Hilfe von gekoppelten Modellen, die vor allem bei der Simulation von Wassermangelsituationen eine wesentliche Rolle spielen. Dazu wurden die notwendigerweise zu berücksichtigenden Prozesse und die Anforderungen seitens der Modellierung diskutiert. Es wurde herausgestellt, dass Rückkopplungen und Wechselwirkungen einerseits zwischen Grund- und Oberflächengewässer, andererseits zwischen Grund- und Bodenwasser unter Einbeziehung der saisonal wechselnden Vegetationswirkung im Modell berücksichtigt werden müssen. Aus einer großen Modellvielzahl wurde das Modellierungssystem ArcEGMO-PSCN-ASM als geeignet ausgewählt und für diese Fragestellung weiterentwickelt. Die Interaktionen zwischen Oberflächen- und Grundwasser wurden anhand verschiedener Modellsimulationen analysiert. Der Austausch zwischen Fließgewässer und Grundwasser, sowie die Rückwirkung der Grundwasserstände auf das Oberflächenwasser zeigte den größten Einfluss auf die Modellergebnisse. Die Wasserstandsdynamik in den Fließgewässern und der Kapillaraufstieg zeigten nur lokale Effekte. Die Praxistauglichkeit des gekoppelten Modells wurde in zwei Fallbeispielen getestet, die sich mit verschiedenen Lösungen zur Bekämpfung von Wassermangelsituationen beschäftigen. Die Ergebnisse der Simulationen zeigen deutlich, dass mit Hilfe des gekoppelten Modells Bewirtschaftungsmaßnahmen im Gewässer selbst sowie im ober- und unterirdischen Einzugsgebiet adäquat abgebildet und quantitative Aussagen mit einer hohen Praxisrelevanz gewonnen werden können. Diese Arbeit leistet damit sowohl einen wissenschaftlichen Beitrag zum Modellverständnis als auch den Nachweis einer praktikablen Modellanwendung in unterschiedlichen Einzugsgebieten.The modeling of all relevant runoff processes in a catchments area is indispensable considering the actual questions (like Water Framework Directive and climatic change). This investigation aims the quantitative analysis and demonstration of surface- and subsurface water interactions, which are relevant for simulating northeastern German regions with water scarcity, by using coupled models. Therefore processes, which necessarily must be considered, and requirements on the part of the modeling, were discussed. It was exposed / presented that feedbacks and interactions of surface water and subsurface water on one hand and (oder besser: as well as?) groundwater and soil water including seasonal vegetation development on the other hand must be considered in the model. The modeling system ArcEGMO-PSCN-ASM was chosen / selected out of a huge amount of models as appropriate for this task. It was further adopted / developed to this task in co-operation with Dr. Pfützner (BAH-Berlin). The interactions of surface water and groundwater where analyzed by various simula-tions. The exchange between stream water and groundwater as well as the feedback of groundwater levels to surface water had the most influence to the model results. Dynamic stream water levels and capillary rise had only local effects and low impact on the catchments average. The suitability for practical use of this coupled model where tested at two sample areas, with various solutions to deal with water scarcity. The model results illustrate clearly that using coupled models water management treatments as well in the river itself as in surface and subsurface catchment areas can be shown adequately and quantitative statements with a high practice relevance can be achieved. The results of the present study contribute both a scientific contribution to the model understanding and the proof of a practicable application of models in different catchment areas
1-, 2- and 3-dimensional simulation of the water dynamics of africultural sites using the physically based modeling system "HILLFLOW"
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