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  • 1
    In: Fundamental and Applied Limnology / Archiv für Hydrobiologie, June 2014, Vol.184(3), pp.173-181
    Description: Heat is increasingly used as a natural tracer to quantify water fluxes at the groundwater-surface water-interface. We present a systematic approach to monitor and evaluate stream and streambed temperatures to derive daily-updated temperature-based water exchange fluxes between the stream and the streambed. Specifically designed multi-level temperature sensors coupled with a data logger and GSM modem are used to monitor temperature in the stream and streambed and transfer this data daily to a database. A suite of MATLAB scripts with structured query language (SQL) commands is applied to extract the data for processing using an inverse numerical model to estimate water flow based on the measured temperatures. Compared to common analytical approaches, which typically require sinusoidal diurnal temperature pattern, our numerical model can utilize temperature records without daily variations. Temperature-based calculations to quantify vertical water fluxes at the stream-groundwater interface can provide a supplement to, or even a replacement of, calculations based on vertical hydraulic gradients and Darcy' law.
    Keywords: Groundwater - Surface Water - Interface
    ISSN: 1863-9135
    E-ISSN: 23637110
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  • 2
    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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  • 3
    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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  • 4
    In: Ecohydrology, January 2016, Vol.9(1), pp.93-100
    Description: We investigated changes in respiration across nighttime and daytime in a headwater stream. For this, we conducted consecutive nighttime and daytime experiments injecting the bioreactive tracer resazurin in two reaches with different riparian canopy densities (different levels of photosynthetically active radiation) to compare respiration rate coefficients. We found that even though stream water temperatures measured above the streambed at day and night (half‐day timescale) were different within each reach and across reaches (95% confidence level), apparent respiration rate coefficients were not different across nighttime and daytime conditions (95% confidence level). A likely explanation for this is that the bulk of stream respiration takes place in the hyporheic zone, where diel fluctuations of stream temperature and photosynthetically active radiation are considerably attenuated and where temperature is not measured in routine investigations of stream metabolism. Our results suggest that community respiration in headwater streams may not need to be ‘corrected’ for temperature between daytime and nighttime, even though instantaneous changes in respiration are expected to occur from a pure biological perspective. Copyright © 2015 John Wiley & Sons, Ltd.
    Keywords: Community Respiration ; Resazurin ; Smart Tracers ; Diel Fluctuations ; Headwater Stream ; Hyporheic Zone ; Stream Temperature ; Stream Metabolism
    ISSN: 1936-0584
    E-ISSN: 1936-0592
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  • 5
    Language: English
    In: Advances in Water Resources, 2010, Vol.33(11), pp.1309-1319
    Description: Analytical solutions to the one-dimensional heat transport equation for steady-state conditions can provide simple means to quantify groundwater surface water exchange. The errors in exchange flux calculations that are introduced when the underlying assumptions of homogeneous sediments and constant temperature boundary conditions are violated were systematically evaluated in a simulation study. Temperatures in heterogeneous sediments were simulated using a numerical model. Heterogeneity in the sediments was represented by discrete, binary geologic units. High contrasts between the hydraulic conductivities ( ) of the geologic units were found to lead to large errors, while the influence of the structural arrangement of the units was smaller. The effects of transient temperature boundary conditions were investigated using an analytical equation. Errors introduced by transient boundary conditions were small for Darcy-velocities 〉 0.1 m d in the period near maximum and minimum annual surface water temperatures. For smaller fluxes, however, errors can be large. Assuming steady-state conditions and vertical flow in homogeneous sediments is acceptable at certain times of the year and for medium to high exchange fluxes, but pronounced geologic heterogeneity can lead to large errors.
    Keywords: Groundwater–Surface Water Interaction ; Streambed Temperatures ; Geologic Heterogeneity ; Heat Transport Modelling ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 6
    In: Water Resources Research, February 2014, Vol.50(2), pp.1847-1855
    Description: This paper introduces the special section on “new modeling approaches and novel experimental technologies for improved understanding of process dynamics at aquifer‐surface water interfaces.” It is contextualizing the framework for the 27 research papers of the special section by firth identifying research gaps and imminent challenges for ecohydrological research at aquifer‐surface water interfaces and then discussing the specific paper contributions on (i) new developments in temperature/heat tracing at GW‐SW interfaces, (ii) new methods to capture the temporal and spatial variability of groundwater—surface water exchange, (iii) new approaches in modeling aquifer‐river exchange flow, and (iv) new concepts and advanced theory of groundwater—surface water exchange.
    Keywords: Groundwater ; Surface Water ; Hyporheic Zones ; Lacustrine Groundwater Discharge
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 7
    In: Journal of Geophysical Research: Biogeosciences, August 2016, Vol.121(8), pp.2199-2215
    Description: Aerobic respiration is an important component of in‐stream metabolism. The larger part occurs in the streambed, where it is difficult to directly determine actual respiration rates. Existing methods for determining respiration are based on indirect estimates from whole‐stream metabolism or provide time invariant results estimated from oxygen consumption measurements in enclosed chambers that do not account for the influence of hydrological changes. In this study we demonstrate a simple method for determining time‐variable hyporheic respiration. We use a windowed cross‐correlation approach for deriving time‐variable travel times from the naturally changing electrical conductivity signal that is transferred into the sediment. By combining the results with continuous in situ dissolved oxygen measurements, variable oxygen consumption rate coefficients in the streambed are obtained. An empirical temperature relationship is derived and used for standardizing the respiration rate coefficients to isothermal conditions. For demonstrating the method, we compare two independent measurement spots in the streambed, which were located upstream and downstream of an in‐stream gravel bar and thus exposed strongly diverse travel times. The derived respiration rate results are in accordance with findings of other stream studies. By comparing the travel time and respiration rate coefficient (i.e., Damköhler number) we estimate the contribution of each to the oxygen consumption in the streambed. An in situ method for estimation of streambed respiration Natural variations of EC can be used for deriving time‐variable travel times Respiration is equally influenced by temperature and hydrological dynamics
    Keywords: Respiration ; Streambed ; Oxygen ; Electrical Conductivity ; Cross Correlation
    ISSN: 2169-8953
    E-ISSN: 2169-8961
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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.2178-2194
    Description: There is growing interest in riverbed temperature due to the ecological and biogeochemical significance of the hyporheic zone, and its potential to moderate river temperature. Riffles exhibit complex thermal behaviour, hypothesized to be caused by local alteration of groundwater–surface water (GW–SW) interactions, but hitherto most research has been in upland/gravel‐bed/hard rock catchments. Accordingly, this article aims: (1) to characterize spatio‐temporal variability in hyporheic temperature over two riffles (R1 and R2) in a lowland river basin (Tern, Shropshire, UK) underlain by sandstone, and (2) to explain thermal dynamics by inferring hyporheic processes and the influence of GW–SW interactions. Hyporheic (riffle head, crest and tail at 0·1, 0·2 and 0·4 m), water column, spring water and air temperature were collected at 15 min resolution over 22 months and used to explore seasonal variations. Borehole water levels and temperature provide insight into groundwater variability over a hydrological year. Hyporheic temperature is cooler (warmer) than water column in summer (winter), with convergence in spring and autumn. Riffle heads and R2 crest yield small thermal gradients, and R1 tail larger vertical difference. R1 crest temperature is similar and attenuated (cf. water column) at all depths. R2 tail temperature differs markedly from surface water. Thus, hyporheic temperature varies temporally across and between riffles, reflecting: (1) hydroclimatological controls on river and groundwater temperature, and (2) hydrological, local morphological and sedimentary controls on surface water and groundwater flux. This research demonstrates the utility of depth‐related riverbed temperature time‐series in understanding hyporheic zone processes and GW–SW interactions. Copyright © 2009 John Wiley & Sons, Ltd.
    Keywords: Water Temperature ; Thermal Regime ; Riverbed ; Hyporheic Zone ; Groundwater–Surface Water Interactions ; Sandstone ; River Tern
    ISSN: 0885-6087
    E-ISSN: 1099-1085
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