Ecohydrology on the edge: interactions across the interfaces of wetland, riparian and groundwater‐based ecosystems

Krause, Stefan; Hannah, David M.; Sadler, John; Wood, Paul J.

doi:10.1002/eco.240

Cited by 23 publications

(18 citation statements)

References 37 publications

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“…However, as result of the depositional history of the river system, exchange flow between groundwater and surface water can be spatially highly heterogeneous, causing complex flow patterns at the aquifer-river interface (Fleckenstein et al, 2006;Lowry et al, 2007;Rosenberry and Pitlick, 2009). Uncertainty in the detection of exchange flow patterns increases with increasing spatial scale (White, 1993;Kasahara and Wondzel, 2003;Krause et al, 2009aKrause et al, , 2011a, with crucial implications for the (un)certainty of predictions of HZ biogeochemical and ecohydrological functioning (Brunke and Gonser, 1997;Boulton et al, 1998;Krause et al, 2011c).…”

Section: Motivation: the Importance Of Groundwatersurface Water Exchamentioning

confidence: 99%

Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

Krause

Blume

Cassidy

2012

Hydrol. Earth Syst. Sci.

140

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Abstract. This paper investigates the patterns and controls of aquifer-river exchange in a fast-flowing lowland river by the conjunctive use of streambed temperature anomalies identified with Fibre-optic Distributed Temperature Sensing (FO-DTS) and observations of vertical hydraulic gradients (VHG).FO-DTS temperature traces along this lowland river reach reveal discrete patterns with "cold spots" indicating groundwater up-welling. In contrast to previous studies using FO-DTS for investigation of groundwater-surface water exchange, the fibre-optic cable in this study was buried in the streambed sediments, ensuring clear signals despite fast flow and high discharges. During the observed summer baseflow period, streambed temperatures in groundwater up-welling locations were found to be up to 1.5 • C lower than ambient streambed temperatures. Due to the high river flows, the cold spots were sharp and distinctly localized without measurable impact on down-stream surface water temperature.VHG patterns along the stream reach were highly variable in space, revealing strong differences even at small scales. VHG patterns alone are indicators of both, structural heterogeneity of the stream bed as well as of the spatial heterogeneity of the groundwater-surface water exchange fluxes and are thus not conclusive in their interpretation. However, in combination with the high spatial resolution FO-DTS data we were able to separate these two influences and clearly identify locations of enhanced exchange, while also obtaining information on the complex small-scale streambed transmissivity patterns responsible for the very discrete exchange patterns. The validation of the combined VHG and FO-DTS approach provides an effective strategy for analysing drivers and controls of groundwater-surface water exchange, with implications for the quantification of biogeochemical cycling and contaminant transport at aquifer-river interfaces.

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Section: Motivation: the Importance Of Groundwatersurface Water Exchamentioning

confidence: 99%

Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

Krause

Blume

Cassidy

2012

Hydrol. Earth Syst. Sci.

140

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“…[2] Anthropogenic alterations of the nitrogen cycle have been found to often cause adverse impacts on groundwater and surface water quality and habitat conditions [McMahon and Bohlke, 1996;Brunke and Gonser, 1997;Duff and Triska, 2000;Robertson and Wood, 2010;Krause et al, 2011aKrause et al, , 2011bKrause et al, , 2011c, and are considered to represent a growing environmental problem of global concern [Seitzinger, 1988;Vitousek et al, 1997;Seitzinger et al, 2006;Schlesinger et al, 2006;Diaz and Rosenberg, 2008;Galloway et al, 2008].…”

Section: Introductionmentioning

confidence: 99%

Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river

et al. 2013

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[1] Biogeochemical turnover in hyporheic zones is known to have the potential to affect the chemical signature of surface water cycling through shallow streambed sediments. This study investigates the impact of streambed physical properties on the fate of nitrate and dissolved oxygen in groundwater upwelling through the streambed of a lowland river. For analyzing depth-dependent patterns and zonation of nitrogen concentrations, diffuse gel probes in shallow (top 15 cm) streambed sediments have been deployed in a nested setup together with multilevel minipiezometers for streambed sediments of 15-150 cm. Spatial heterogeneity of groundwater upwelling was controlled by patterns of low-conductivity peat and clay strata that caused locally confined conditions, suggesting increased streambed residence times. Nitrate concentrations in the upwelling groundwater changed by up to 68.06 mg L À1 within the top 15 cm of streambed sediments and by up to 107.47 mg L À1 at depths of 15-150 cm, indicating that significant nitrogen turnover was not restricted to shallow streambed sediments. Intensive reduction of nitrate concentrations was found, in particular, in vicinity of low-conductivity streambed strata. The coincidence of confined groundwater upwelling and reduced oxygen concentrations at these locations suggests that increased residence times and associated depletion of dissolved oxygen create conditions favorable for nitrate reduction. Our results highlight that increased nitrogen turnover at aquifer-river interfaces is not necessarily limited to shallow streambed zones, where surface water is mixing with groundwater, but can affect upwelling groundwater in reactive hot spots that extend to greater streambed depths and beyond hyporheic mixing zones.Citation: Krause, S., C. Tecklenburg, M. Munz, and E. Naden (2013), Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river,

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“…The mixing of groundwater and surface water can have substantial impact on stream and streambed thermal patterns [ Malcolm et al ., ; Hannah et al ., ; Krause et al ., ], the availability of dissolved oxygen, nutrient cycling and carbon respiration [ Pinay et al ., ; Mulholland et al ., ; Krause et al ., ; Pinay et al ., ; Zarnetske et al ., ], transport and transformation of contaminants [ Conant et al ., ; Ellis and Rivett , ; Rivett et al ., ], as well as the ecohydrological functioning of the riverine environment [ Brunke and Gonser , ; Dole‐Olivier et al ., ; Boulton et al ., ; Malcolm et al ., 2002; Stubbington et al ., ; Robertson and Wood , ; Krause et al ., ]. A major challenge for quantifying the impact of physical streambed controls on the biogeochemical and ecohydrological functioning is the difficulty to identify temporal dynamics and detailed spatial patterns of groundwater‐surface water exchange at stream reach and larger scales [ White , ; Krause et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Impact of seasonal variability and monitoring mode on the adequacy of fiber‐optic distributed temperature sensing at aquifer‐river interfaces

Krause

Blume

2013

Water Resources Research

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[1] Fiber-optic distributed temperature sensing (FO-DTS) has been frequently applied for analyzing thermal patterns, including the identification of groundwater-surface water exchange fluxes across aquifer-river interfaces. However, the impacts of (a) seasonal variability in signal strength (given by the difference between groundwater and surface water temperatures) and (b) monitoring modes on the accuracy of FO-DTS surveys have not yet been determined. This study uses a well-investigated field site as model system for quantifying the accuracy and uncertainty of FO-DTS surveys in dependency of seasonal signal variation and monitoring mode. The analysis of the relationship between seasonal variability in signal strength and diurnal oscillations in end-member temperatures at the study site revealed that winter conditions, with substantially lower diurnal temperature oscillations, provide the highest temporal stability in signal strength. The choice of monitoring mode proved to have significant impact on the accuracy of FO-DTS surveys. The proposed two-way single-ended averaging of FO-DTS surveys had significant advantages compared to single-ended or double-ended surveys, with a higher accuracy in signal detection, in particular for small-scale temperature variations. Since FO-DTS surveys in two-way single-ended averaging mode were better suited for detecting the full complexity of spatial temperature patterns for the investigated aquifer-river interface, we recommend its wider application in similarly complex systems with small-scale thermal patterns.Citation: Krause, S., and T. Blume (2013), Impact of seasonal variability and monitoring mode on the adequacy of fiber-optic distributed temperature sensing at aquifer-river interfaces, Water Resour.

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Ecohydrology on the edge: interactions across the interfaces of wetland, riparian and groundwater‐based ecosystems

Cited by 23 publications

References 37 publications

Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

Investigating patterns and controls of groundwater up-welling in a lowland river by combining Fibre-optic Distributed Temperature Sensing with observations of vertical hydraulic gradients

Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river

Impact of seasonal variability and monitoring mode on the adequacy of fiber‐optic distributed temperature sensing at aquifer‐river interfaces

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