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  • 1
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    Airborne Thermal Data Identifies Groundwater Discharge at the North-Western Coast of the Dead Sea (2018)
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    Publication Date: 2021-03-29
    Description: A qualitative and quantitative monitoring of groundwater discharge was conducted based on an airborne thermal campaign undertaken along the north-western coast of the Dead Sea in January 2011 to contribute to the relatively scarce information on groundwater discharge to date in the region. The application of airborne thermal data exploits thermal contrasts that exist between discharging groundwater and background sea surface temperatures of the Dead Sea. Using these contrasts, 72 discharge sites were identified from which only 42 were known from previous in situ measurements undertaken at terrestrial springs by the Israel Hydrological Service. Six of these sites represent submarine springs and at a further 24 locations groundwater appears to seep through the sediment. Although the abundance of groundwater seepage sites suggests a significant, but so far unknown groundwater source, the main contribution appears to originate from terrestrial springs. In an attempt to provide a quantitative approach for terrestrial springs, a linear bootstrap regression model between in situ spring discharge and respective thermal discharge plumes (r2 = 0.87 p 〈 0.001) is developed and presented here. While the results appear promising and could potentially be applied to derive discharge values at unmonitored sites, several influence factors need to be clarified before a robust and reliable model to efficiently derive a complete quantitative picture of groundwater discharge can be proposed.
    Keywords: thermal discharge plume; groundwater discharge; ; 551
    Language: English
    Type: article , publishedVersion
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  • 2
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    Microbial and Chemical Characterization of Underwater Fresh Water Springs in the Dead Sea (2018)
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    Publication Date: 2021-03-29
    Description: Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea - Dead Sea water conduit.
    Keywords: Dead Sea; Archaeal community ; 551
    Language: English
    Type: article , publishedVersion
    Format: 21
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  • 3
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    Simulation of saturated and unsaturated flow in karst systems at catchment scale using a double continuum approach (2018)
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    Publication Date: 2021-03-29
    Description: The objective of this work is the simulation of saturated and unsaturated flow in a karstified aquifer using a double continuum approach. The HydroGeoSphere code ( Therrien et al. , 2006 ) is employed to simulate spring dis- charge with the Richards equations and van Genuchten pa- rameters to represent flow in the (1) fractured matrix and (2) conduit continuum coupled by a linear exchange term. Rapid vertical small-scale flow processes in the unsaturated conduit continuum are accounted for by applying recharge boundary conditions at the bottom of the saturated model do- main. An extensive sensitivity analysis is performed on sin- gle parameters as well as parameter combinations. The tran- sient hydraulic response of the karst spring is strongly con- trolled by the matrix porosity as well as the van Genuchten parameters of the unsaturated matrix, which determine the head dependent inter-continuum water transfer when the con- duits are draining the matrix. Sensitivities of parameter com- binations partially reveal a non-linear dependence over the parameter space. This can be observed for parameters not belonging to the same continuum as well as combinations, which involve the exchange parameter, showing that results of the double continuum model may depict a certain de- gree of ambiguity. The application of van Genuchten pa- rameters for simulation of unsaturated flow in karst systems is critically discussed.
    Keywords: saturated unsaturated flow; karst systems; catchment scale; double continuum ; 551
    Language: English
    Type: article , publishedVersion
    Format: 15
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  • 4
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    Influence of aquifer heterogeneity on karst hydraulics and catchment delineation employing distributive modeling approaches (2018)
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    Publication Date: 2021-03-29
    Description: Due to their heterogeneous nature, karst aquifers pose a major challenge for hydrogeological investigations. Important procedures like the delineation of catchment areas for springs are hindered by the unknown locations and hy- draulic properties of highly conductive karstic zones. In this work numerical modeling was employed as a tool in delineating catchment areas of several springs within a karst area in southwestern Germany. For this purpose, different distributive modeling approaches were implemented in the finite element simulation software Comsol Multiphysics ® . The investigation focuses on the question to which degree the effect of karstification has to be taken into account for accurately simulating the hydraulic head distribution and the observed spring discharges. The results reveal that the representation of heterogeneities has a large influence on the delineation of the catchment areas. Not only the location of highly conductive elements but also their geometries play a major role for the resulting hydraulic head distribution and thus for catchment area de- lineation. The size distribution of the karst conduits derived from the numerical models agrees with knowledge from karst genesis. It was thus shown that numerical modeling is a use- ful tool for catchment delineation in karst aquifers based on results from different field observations.
    Description: Open-Access-Publikationsfonds 2013
    Keywords: karst aquifer; hydraulics; ; 551
    Language: English
    Type: article , publishedVersion
    Format: 14
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  • 5
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    Reducing the ambiguity of karst aquifer models by pattern matching of flow and transport on catchment scale (2018)
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    Publication Date: 2021-03-29
    Description: Open-Access-Publikationsfonds 2014
    Keywords: karst aquifer; flow; Transport; catchment scale ; 551
    Language: English
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  • 6
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    Representation of water abstraction from a karst conduit with numerical discrete-continuum models (2018)
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    Publication Date: 2021-03-29
    Description: Karst aquifers are characterized by highly conductive conduit flow paths embedded in a less conductive fissured and fractured matrix, resulting in strong permeability contrasts with structured heterogeneity and anisotropy. Groundwater storage occurs predominantly in the fissured matrix. Hence, most mathematical karst models assume quasi-steady-state flow in conduits neglecting conduitassociated drainable storage (CADS). The concept of CADS considers storage volumes, where karst water is not part of the active flow system but hydraulically connected to conduits (for example karstic voids and large fractures). The disregard of conduit storage can be inappropriate when direct water abstraction from karst conduits occurs, e.g., largescale pumping. In such cases, CADS may be relevant. Furthermore, the typical fixed-head boundary condition at the karst outlet can be inadequate for water abstraction scenarios because unhampered water inflow is possible. The objective of this work is to analyze the significance of CADS and flow-limited boundary conditions on the hydraulic behavior of karst aquifers in water abstraction scenarios. To this end, the numerical discrete-continuum model MODFLOW-2005 Conduit Flow Process Mode 1 (CFPM1) is enhanced to account for CADS. Additionally, a fixed-head limited-flow (FHLQ) boundary condition is added that limits inflow from constant head boundaries to a user-defined threshold. The effects and the proper functioning of these modifications are demonstrated by simplified model studies. Both enhancements, CADS and FHLQ boundary, are shown to be useful for water abstraction scenarios within karst aquifers. An idealized representation of a large-scale pumping test in a karst conduit is used to demonstrate that the enhanced CFPM1 is able to adequately represent water abstraction processes in both the conduits and the matrix of real karst systems, as illustrated by its application to the Cent Fonts karst system.
    Keywords: water abstraction; karst; ; 551
    Language: English
    Type: article , publishedVersion
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  • 7
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    Localisation and temporal variability of groundwater discharge into the Dead Sea using thermal satellite data (2018)
    Springer-Verlag | Berlin/Heidelberg
    Details
    Publication Date: 2021-03-29
    Keywords: Landsat ETM+; Sea surface temperature; Submarine groundwater discharge; Groundwater resource ; 551 ; Earth Sciences; Geology
    Language: English
    Type: article , publishedVersion
    Format: application/pdf
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  • 8
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    Zum Vorkommen des Ufer-Torfmooses Sphagnum riparium ÅNGSTR. im Arnsberger Wald (Nordrhein-Westfalen) (2018)
    Details
    Publication Date: 2021-03-29
    Description: Abstract: The range extension, phytosociology and ecology of Sphagnum riparium for the Arnsberger Wald, the largest forest area in North Rhine-Westphalia (Germany) are discussed in detail. The occurrence of Sphagnum riparium in the Arnsberger Wald seems to be the furthermost northwest exposed subarea in central Europe of this species. Major aspects are the distinct floristic structure primarely referring to communities of open fens and the specific habitat preferences illustrating a remarkable hydrological and micro-climatically stability. The analysis of the hydrochemical properties indicates poor nutrition conditions, but moderate base availabilities at the sites examined. In addition the endangerment of the Sphagnum riparium-rich habitats in the Arnsberger Wald is described.
    Description: Zusammenfassung: Sphagnum riparium besitzt im Arnsberger Wald einen regionalen Verbreitungsschwerpunkt, wobei es sich um das am weitesten nach Nordwesten exponierte Teilareal dieser Art in Mitteleuropa handelt. Das Torfmoos kommt v. a. in lichten, quellnahen Sumpf- und Moorwäldern in den höheren Lagen dieses Waldgebietes vor und hat hier unter Optimalbedingungen relativ ausgedehnte und vitale Be stände aufgebaut. Die hydrochemischen Messwerte belegen, dass sich die Standorte der überprüften Sphagnum riparium-reichen Phytozönosen im Arnsberger Wald durch eingeschränkte Nährstoffverfügbarkeiten, aber auch durch günstigere Basengehalte auszeichnen. Sie sind pflanzensoziologisch überwiegend den Niedermoor-Gesellschaften des Caricion nigrae anzuschließen und lassen sich in fünf floristisch und z. T. auch ökohydrologisch gut charakterisierbare Vegetationseinheiten gruppieren.
    Description: DFG, SUB Göttingen, DGMT
    Description: research
    Keywords: 553.21 ; Moor ; Sphagnum ; mire ; peatland ; vegetation ; Niedermoor ; fen ; FID-GEO-DE-7
    Language: German
    Type: article , publishedVersion
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