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Berlin Brandenburg

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  • 1
    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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  • 2
    Language: English
    In: Hydrological Processes, 30 September 2011, Vol.25(20), pp.3244-3255
    Description: The hyporheic zone (HZ) has the capability to eliminate and attenuate nutrients and contaminants in riverine systems. Biogeochemical reactions and the potential elimination of contaminants are strongly controlled by the flow paths and dynamics in the HZ. Nevertheless, an easily applicable method for the field determination of flow patterns in the HZ is still lacking. Therefore, a heat pulse technique, which traces the movement of a short heat pulse in the upper part of the HZ and other sand beds, was developed. Five rods are vertically driven into the sediment of the streambed; one rod with a heater as point source located in about 10‐cm sediment depth and four rods with four temperature sensors in 3 cm distance, arranged concentrically with 7 cm diameter around the heating rod. Subsequently, a heat pulse is applied and the resulting breakthrough curves are indicative of flow velocities and flow directions in the streambed. A rough data analysis procedure is also suggested. In addition, laboratory experiments were performed to test the heat pulse technique. These experiments were validated based on coupled numerical modelling of flow and heat transport. First field tests of the method prove that the method is easily applicable under field conditions. These first field tests showed highly complex flow patterns with flow velocities from 1·8 to 4·9 cm min and flow directions from parallel to surface flow to opposite to surface flow. This suggests the need for a robust method to quantify hyporheic flow patterns . Copyright © 2011 John Wiley & Sons, Ltd.
    Keywords: Flow Direction ; Flow Velocity ; Hyporheic Zone ; Sandy Beds ; Heat Pulse Technique
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 3
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2103-2107
    Description: Abstract not available.
    Keywords: Hydrology ; Hydrologic Analysis ; Hydrology ; Hydrology ; Interfaces ; Hydrology ; General ; General ; General ; General (556);
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 4
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2252-2263
    Description: Despite the widely accepted importance of the hyporheic zone as a habitat for stream macroinvertebrates during floods, few data exist regarding community composition and distribution during periods of low flow or drought in perennial streams. Integrating research on hyporheic invertebrates with results from a long‐term study of a UK river provided the opportunity to examine how benthic and hyporheic macroinvertebrate communities respond to inter‐annual variability in river flow and periods of groundwater drought. Changes in the riverine macroinvertebrate community associated with low flow included a reduction in species richness and the number of individuals per sample, particularly aquatic insects. The hyporheic community was characterized by a relatively homogeneous composition during a period of severe low flow, punctuated by short‐term changes associated with variation in water temperature rather than changes in discharge. We present a conceptual model of the processes influencing benthic and hyporheic invertebrates under low‐flow conditions. Previous studies have seldom integrated these two assemblages and their interactions. The model presented highlights the potential importance of surface water and hyporheic zone linkages for riverine invertebrate communities under a range of flow conditions. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Benthos ; Hyporheos ; Low Flows ; Drought ; Hyporheic Processes ; Invertebrates ; Groundwater
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 5
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2138-2149
    Description: Subsurface flow in streambeds can vary at different scales in time and space. Recognizing this variability is critical for understanding biogeochemical and ecological processes associated with the hyporheic zone. The aim of this study was to examine the variability of hydraulic conductivity (), vertical hydraulic gradients (VHGs), and subsurface fluxes, over a riffle–step–pool sequence and at a high spatio‐temporal resolution. A 20 m reach was equipped with a network of piezometers in order to determine the distribution of VHGs and . During a summer month, temporal variations of VHGs were regularly surveyed and, for a subset of piezometers, the water level was automatically recorded at 15 min intervals by logging pressure transducers. Additionally, point‐dilution tests were carried out on the same subset of piezometers. Whereas the distribution of vertical fluxes can be derived from and VHG values, point‐dilution tests allow for the estimation of horizontal fluxes where no VHG is detectable. Results indicate that, spatially, VHGs switched from upwelling to downwelling across lateral as well as longitudinal sections of the channel. Vertical fluxes appeared spatially more homogeneous than VHGs, suggesting that the latter can be a poor indicator of the intensity of flow. Finally, during flow events, some VHGs showed little or no fluctuations; this was interpreted as the result of a pressure wave propagating from upstream through highly diffusive alluvial sediments. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Hyporheic Exchange Flow ; Heterogeneity ; Hydraulic Conductivity ; Vertical Hydraulic Gradient ; Groundwater–Surface Water Interactions
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 6
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2212-2224
    Description: The hydrochemistry of sulphur in the active outwash plain of Skeiðarársandur, SE Iceland shows considerable variety reflecting differences in sources and processes, and is investigated in this article using δS values of dissolved sulphate and igneous sulphide minerals, δO, and ionic concentrations in waters. Seawater‐derived sulphate is a notable component only in the lower sandur (δS = +6·8‰ VCDT). δS in the Skeiðará glacial melt river range from +3·4 to +8·8‰δS. The higher values occur during a flood event and reflect geothermal sulphate contributions from the Grímsvötn caldera. ‘Kettle‐hole lakes’ formed since the November 1996 jökulhlaup form important ecological niches and show evidence of coupled sulphide oxidation and carbonate and possibly silicate dissolution and have the lowest δS values (average −0·8‰) attributed to higher proportions of sulphide oxidation‐derived SO and/or bacterially mediated sulphide oxidation. The hydrochemistry of eastern sandur groundwater is influenced by a hydrothermal source of reduced sulphur from the Grímsvötn caldera or a localized area of geothermal springs, and contrasts with the hydrochemistry of the majority of groundwaters and the Sulá and Gígjukvísl rivers in western and central Skeiðarársandur. These have lower [Ca + Mg], [Na + K] and SO concentrations and δS values consistent with sulphate derived from the oxidation of igneous sulphides. In comparison to catchments dominated by atmospherically transported sulphate, catchments such as this where the sulphur system is dominated by internal sources (rock‐derived and geothermal) will not be sensitive to the temporal decreasing trends in contributions from long‐range airborne sulphate resulting from reductions of sulphur emissions in North America and Europe. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Sulphur Isotopes ; Sulphate ; Kettle‐Hole Lakes ; Geothermal Water ; Jökulhlaups ; Chemical Weathering
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 7
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2267-2274
    Description: No Abstract. Abstract Copyright (2009), Wiley Periodicals, Inc.
    Keywords: Hydrogeology ; Ground Water ; Hydrology ; Hyporheic Zone ; Methods ; Models ; Rivers And Streams ; Surface Water ; Water Management ; Water Resources;
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 8
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2225-2238
    Description: We investigated the accumulation and biogeochemical cycling of organic matter beneath plants in a lowland river. Organic carbon accumulated beneath the plants at a mean rate of 20 mmol C m h. Annual gross primary production for both and its biofilm, and the microphytobenthos, could account for 26% of the carbon accumulated. The remainder was attributable to organic carbon in both suspended particulate matter (77%) and that associated with sands saltating along the bottom (33%). Maximum carbon oxidation occurred in spring and early summer and declined thereafter. The efflux of CO was greater than the carbon equivalents due to reduction of O, NO and SO measured at the surface, which suggested a significant contribution to carbon oxidation from the subsurface and some oxidation via alternative electron acceptors. The peak in carbon oxidation could not be accounted for by either rising temperature or primary production but tracked the quality of recently deposited allochthonous organic matter. The ratio of carbon oxidation to total organic carbon accumulation suggested that 19% of the organic matter deposited was remineralised on an annual basis, although this reached 58% in June. We calculate that a total of 3·6 mol N m y was mineralised in the sediment, of which 11% could be accounted for by the measured efflux of NH. The remainder could be accounted for by the N demand from primary production (67% macrophytes/biofilm; 36% phytobenthos). Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Hyporheic Zone ; Biogeochemical ; Fine Sediment ; Aquatic Vegetation ; Organic Carbon Budget ; Carbon ; Cycling ; Sediments
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 9
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2150-2164
    Description: Thermal stream loadings from both natural and anthropogenic sources have significant relevance with respect to ecosystem health and water resources management, particularly in the context of future climate change. In recent years, there has been an increase in field‐based research directed towards characterizing thermal energy transport exchange processes that occur at the surface water/groundwater interface of streams. In spite of this effort, relatively little work has been performed to simulate these exchanges and elucidate their roles in mediating surface water temperatures and to simultaneously take into account all the pertinent hydrological, meteorological and surface/variably‐saturated subsurface processes. To address this issue, HydroGeoSphere, a fully‐integrated surface/subsurface flow and transport model, was enhanced to include fully integrated thermal energy transport. HydroGeoSphere can simulate water flow, evapotranspiration, and advective‐dispersive heat and solute transport over the 2D land surface and water flow and heat and solute transport in the 3D subsurface under variably saturated conditions. In this work, the new thermal capabilities of HydroGeoSphere are tested and verified by comparing HydroGeoSphere simulation results to those from a previous subsurface thermal groundwater injection study and also by simulating an example of atmospheric thermal energy exchange. High‐resolution 3D numerical simulations of a well‐characterized reach of the Pine River in Ontario, Canada are also presented to demonstrate thermal energy transport in an atmosphere–groundwater–surface water system. The HydroGeoSphere simulation successfully matched the spatial variations in the thermal patterns observed in the riverbed, the surface water and the groundwater. The computational framework can be used to provide quantitative guidance towards establishing the conditions needed to maintain a healthy ecosystem. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Thermal Energy Transport ; Fully Integrated Surface/Subsurface Model ; Thermal Stream Loadings
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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  • 10
    Language: English
    In: Hydrological Processes, 15 July 2009, Vol.23(15), pp.2117-2128
    Description: Hydrological exchange processes in the floodplain of a lowland groundwater‐surface water system with emphasis to the hyporheic zone are studied on the basis of an experimental site surrounded by an oxbow and the current bed of the river Spree. Water levels were collected in 12 piezometers and 2 recording stage gauges of a 300‐m long transect throughout a 1‐year‐period. Due to clogging the hydraulic contact between the oxbow and the adjacent aquifer is marginal. Fluctuating river gauges cause an alternation of infiltration and exfiltration. Most of the time groundwater flux is directed into the river Spree while infiltration events are usually short. The largest infiltration event in the 1‐year‐period reached about 4 m into the aquifer. On the basis of a principal component analysis two major processes controlling water level fluctuations in the aquifer are identified. The first component responsible for about 70% of the fluctuations stands for the dampening and delay of fluctuations of the river gauge spreading into the aquifer. The second component explaining about 20% of the fluctuations stands for groundwater recharge due to precipitation events. In lower reaches with extended floodplains, fluctuations of groundwater levels are mainly controlled by river gauges and thus, the hydrological conditions in upstream reaches. In contrast local precipitation events are of minor importance and upslope groundwater level fluctuations are completely unimportant. A cross correlation of the times series of the different piezometers was used to calculate the time lag of pressure fluctuations at different locations and resulted in a propagation of the pressure fluctuations of about 1550 m d while the effective velocity of the groundwater was about 1000 times smaller. Fast water level fluctuations should not be misinterpreted as fast flow velocities and special care is necessary in flow modelling of such data sets since most groundwater flow models cannot cope with a fast propagation of pressure head fluctuations. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Surface Water‐Groundwater Interactions ; Floodplain ; Infiltration ; Pressure Head Fluctuations ; Clogging ; Principal Component Analysis
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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