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  • 1
    Language: English
    In: Journal of Hydrology, Dec 19, 2012, Vol.475, p.1(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2012.06.050 Byline: Lisa Angermann (a)(b)(c), Jorg Lewandowski (a), Jan H. Fleckenstein (b)(c), Gunnar Nutzmann (a)(d) Keywords: Flow patterns; Flow direction; Flow velocity; Hyporheic zone; Heat pulse technique Abstract: a* We developed a method to determine flow direction and velocity in the hyporheic zone. a* The method is based on a heat pulse technique with analytical data analysis algorithm. a* Error-proneness and accuracy of the method were assessed in the lab and in situ. a* The first field application gives insight in hyporheic flow patterns of a lowland river. Author Affiliation: (a) Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department Ecohydrology, Muggelseedamm 310, D-12587 Berlin, Germany (b) Helmholtz Center for Environmental Research - UFZ, Department of Hydrogeology, Permoserstr. 15, D-04318 Leipzig, Germany (c) University of Bayreuth, Department of Hydrology, Universitatsstr. 30, D-95440 Bayreuth, Germany (d) Humboldt-University of Berlin, Geographical Institute, Rudower Chaussee 16, D-12489 Berlin, Germany Article History: Received 27 October 2011; Revised 21 June 2012; Accepted 26 June 2012 Article Note: (miscellaneous) This manuscript was handled by Philippe Baveye, Editor-in-Chief, with the assistance of Nunzio Romano, Associate Editor
    Keywords: Hydrogeology -- Analysis ; Sensors -- Analysis ; Flow (Dynamics) -- Analysis
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Journal of Hydrology, Feb 13, 2014, Vol.509, p.601(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.12.005 Byline: Svenja Bartsch, Sven Frei, Marianne Ruidisch, Christopher L. Shope, Stefan Peiffer, Bomchul Kim, Jan H. Fleckenstein Abstract: acents Temporal variability of river-aquifer exchange fluxes is controlled by the monsoon. acents Monsoonal extreme precipitation events are dominant drivers for flow reversals. acents Frequent flow reversals affect the local water quality. Article History: Received 26 August 2013; Revised 3 December 2013; Accepted 5 December 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of Philippe Negrel, Associate Editor
    Keywords: Aquifers ; Rain ; Climate
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Journal of Hydrology, October 2015, Vol.529, pp.969-979
    Description: Coupling surface and subsurface water flow in fully integrated hydrological codes is becoming common in hydrological research; however, the coupling of surface–subsurface solute transport has received much less attention. Previous studies on fully integrated solute transport focus on small scales, simple geometric domains, and have not utilised many different field data sources. The objective of this study is to demonstrate the inclusion of both flow and solute transport in a 3D, fully integrated catchment model, utilising high resolution observations of dissolved organic carbon (DOC) export from a wetland complex during a rainfall event. A sensitivity analysis is performed to span a range of transport conditions for the surface–subsurface boundary (e.g. advective exchange only, advection plus diffusion, advection plus full mechanical dispersion) and subsurface dispersivities. The catchment model captures some aspects of observed catchment behaviour (e.g. solute discharge at the catchment outlet, increasing discharge from wetlands with increased stream discharge, and counter-clockwise concentration–discharge relationships), although other known behaviours are not well represented in the model (e.g. slope of concentration–discharge plots). Including surface–subsurface solute transport aids in evaluating internal model processes, however there are challenges related to the influence of dispersion across the surface–subsurface interface, and non-uniqueness of the solute transport solution. This highlights that obtaining solute field data is especially important for constraining integrated models of solute transport.
    Keywords: Solute Transport ; Surface–Subsurface Coupling ; Integrated Modelling ; Catchment Modelling ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 4
    Language: English
    In: Water Research, 01 March 2018, Vol.130, pp.185-199
    Description: Nitrate contamination in ground- and surface water is a persistent problem in countries with intense agriculture. The transition zone between rivers and their riparian aquifers, where river water and groundwater interact, may play an important role in mediating nitrate exports, as it can facilitate intensive denitrification, which permanently removes nitrate from the aquatic system. However, the in-situ factors controlling riparian denitrification are not fully understood, as they are often strongly linked and their effects superimpose each other. In this study, we present the evaluation of hydrochemical and isotopic data from a 2-year sampling period of river water and groundwater in the riparian zone along a 3rd order river in Central Germany. Based on bi- and multivariate statistics (Spearman's rank correlation and partial least squares regression) we can show, that highest rates for oxygen consumption and denitrification in the riparian aquifer occur where the fraction of infiltrated river water and at the same time groundwater temperature, are high. River discharge and depth to groundwater are additional explanatory variables for those reaction rates, but of minor importance. Our data and analyses suggest that at locations in the riparian aquifer, which show significant river water infiltration, heterotrophic microbial reactions in the riparian zone may be fueled by bioavailable organic carbon derived from the river water. We conclude that interactions between rivers and riparian groundwater are likely to be a key control of nitrate removal and should be considered as a measure to mitigate high nitrate exports from agricultural catchments.
    Keywords: Riparian Zone ; Nitrate Contamination ; Nitrate Stable Isotopes ; River-Groundwater Interaction ; Denitrification ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 5
    In: Hydrological Processes, 30 October 2013, Vol.27(22), pp.3240-3253
    Description: Exchange of groundwater and lake water with typically quite different chemical composition is an important driver for biogeochemical processes at the groundwater‐lake interface, which can affect the water quality of lakes. This is of particular relevance in mine lakes where anoxic and slightly acidic groundwater mixes with oxic and acidic lake water (pH 330 nmol g d) compared to alternating sites (〈220 nmol g d). Although differences in sulfate reduction rates could not be explained solely by different flux rates, they were clearly related to the prevailing groundwater‐lake exchange patterns and the associated pH conditions. Our findings strongly suggest that groundwater‐lake exchange has significant effects on the biogeochemical processes that are coupled to sulfate reduction such as acidity retention and precipitation of iron sulfides. Copyright © 2012 John Wiley & Sons, Ltd.
    Keywords: Groundwater‐Lake Exchange ; Acid Mine Lake ; Seepage Flux ; Ph‐Profiles ; Chloride Profiles ; Acid Neutralization Processes
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 6
    In: Global Change Biology, September 2017, Vol.23(9), pp.e5-e6
    Description: Increasing concentrations of dissolved iron and DOC are likely linked to decreasing nitrogen depositon.
    Keywords: Atmospheric Deposition ; Carbon Cycle ; Nitrogen Biogeochemistry ; Organic Matter ; Riparian Zone ; Water Quality
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 7
    Language: English
    In: Advances in Water Resources, 2010, Vol.33(11), pp.1291-1295
    Description: Interest in groundwater (GW)-surface water (SW) interactions has grown steadily over the last two decades. New regulations such as the EU Water Framework Directive (WFD) now call for a sustainable management of coupled ground- and surface water resources and linked ecosystems. Embracing this mandate requires new interdisciplinary research on GW-SW systems that addresses the linkages between hydrology, biogeochemistry and ecology at nested scales and specifically accounts for small-scale spatial and temporal patterns of GW-SW exchange. Methods to assess these patterns such as the use of natural tracers (e.g. heat) and integrated surface-subsurface numerical models have been refined and enhanced significantly in recent years and have improved our understanding of processes and dynamics. Numerical models are increasingly used to explore hypotheses and to develop new conceptual models of GW-SW interactions. New technologies like distributed temperature sensing (DTS) allow an assessment of process dynamics at unprecedented spatial and temporal resolution. These developments are reflected in the contributions to this Special Issue on GW-SW interactions. However, challenges remain in transferring process understanding across scales. ►Rapidly growing interest in groundwater-surface water exchange processes. ►Research on groundwater-surface water interactions has become multidisciplinary. ►New focus on linkages between hydrology, biogeochemistry and ecology. ►Development of new methods and models to quantify spatial and temporal patterns. ►Challenges remain in transferring process understanding across scales.
    Keywords: Groundwater-Surface Water Interactions ; River-Aquifer Exchange ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 8
    Language: English
    In: Advances in Water Resources, December 2018, Vol.122, pp.60-69
    Description: A systematic understanding of hyporheic flux (HF) and residence times (RT) is important as they are a major control of biogeochemical processing in streambeds. Previous studies addressing the effect of heterogeneity in streambed hydraulic conductivity (K) on HF and RT have come to deviating conclusions depending on the specific study design and the selection of heterogeneity cases being investigated. To more systematically evaluate the effects of conductivity heterogeneity on HF and RT, we simulated hyporheic exchange induced by idealized streambed ripples over a large range of heterogeneities. Conductivity heterogeneity was represented in the simulations in terms of 10,000 different heterogeneity realizations from a geostatistical model based on continuous Gaussian and discrete indicator random fields. We demonstrate that any isotropic homogeneous K-field, as an average of a heterogeneous K-field, can only match RT or HF of the respective heterogeneous K-field, but never both. We found exponential correlations of RT and HF with the variance of heterogeneous conductivity. Based on these correlations, an equivalent anisotropic homogeneous conductivity tensor K can be derived. This equivalent anisotropic K efficiently accounts for the effects of small scale heterogeneity on HF and RT. It can be calculated from the median and variance of the hydraulic conductivity distribution of the targeted heterogeneous sediment, without explicitly characterizing the sediment texture.
    Keywords: Conductivity Heterogeneity ; Hyporheic Exchange ; Residence Time ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 9
    Language: English
    In: Journal of sports science & medicine, December 2017, Vol.16(4), pp.474-479
    Description: Objectives of the study were to compare the effects of a single bout of preventive or regenerative foam rolling (FR) on exercise-induced neuromuscular exhaustion. Single-centre randomised-controlled study was designed. Forty-five healthy adults (22 female; 25±2 yrs) were allocated to three groups: 1) FR of the lower limb muscles prior to induction of fatigue, 2) FR after induction of fatigue, 3) no-treatment control. Neuromuscular exhaustion was provoked using a standardized and validated functional agility short-term fatigue protocol. Main outcome measure was the maximal isometric voluntary force of the knee extensors (MIVF). Secondary outcomes included pain and reactive strength (RSI). Preventive (-16%) and regenerative FR (-12%) resulted in a decreased loss in MIVF compared to control (-21%; p 0.8, p 〈 0.1). Differences over time (p 〈 0.001) between groups regarding pain and RSI did not turn out to be clinically meaningful. A single bout of foam rolling reduces neuromuscular exhaustion with reference to maximal force production. Regenerative rather than preventive foam rolling seems sufficient to prevent further fatigue.
    Keywords: Rehabilitation ; Manual Medicine ; Neuromuscular Fatigue ; Pain Therapy ; Self-Myofascial Release ; Sports Medicine
    ISSN: 1303-2968
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  • 10
    Language: English
    In: Advances in Water Resources, December 2015, Vol.86, pp.133-146
    Description: Dynamics of solute export from catchments can be classified in terms of chemostatic and chemodynamic export regimes by an analysis of concentration–discharge relationships. Previous studies hypothesized that distinct export regimes emerge from the presence of solute mass stores within the catchment and their connectivity to the stream. However, so far a direct link of solute export to identifiable catchment characteristics is missing. Here we investigate long-term time series of stream water quality and quantity of nine neighboring catchments in Central Germany ranging from relatively pristine mountain catchments to agriculturally dominated lowland catchments, spanning large gradients in land use, geology, and climatic conditions. Given the strong collinearity of catchment characteristics we used partial least square regression analysis to quantify the predictive power of these characteristics for median concentrations and the metrics of export regime. We can show that median concentrations and metrics of the export regimes of major ions and nutrients can indeed be inferred from catchment characteristics. Strongest predictors for median concentrations were the share of arable land, discharge per area, runoff coefficient and available water capacity in the root zone of the catchments. The available water capacity in the root zone, the share of arable land being artificially drained and the topographic gradient were found to be the most relevant predictors for the metrics of export regime. These catchment characteristics can represent the size of solute mass store such as the fraction of arable land being a measure for the store of nitrate. On the other hand, catchment characteristics can be a measure for the connectivity of these solute stores to the stream such as the fraction of tile drained land in the catchments. This study demonstrates the potential of data-driven, top down analyses using simple metrics to classify and better understand dominant controls of solute export from catchments.
    Keywords: Water Quality ; Catchment ; Nutrient Export ; Tile Drain ; Export Regime ; Concentration–Discharge Relationships ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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