Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream: combining hydraulic and tracer methods

Poulsen, Jens Aage; Sebok, Eva; Duque, Carlos; Tetzlaff, Doerthe; Engesgaard, Peter

doi:10.5194/hess-19-1871-2015

Cited by 35 publications

(41 citation statements)

References 66 publications

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“…As a sedimentation/scouring constraint, streambed elevation changes at the potential high‐discharge locations could not exceed ±0.05 m compared with the initial elevation of 13 October 2011 to exclude the effects of sedimentation and scouring in the data interpretation. Being a groundwater‐fed stream with groundwater discharge of variable upward fluxes (Karan et al ., ) everywhere along the stream channel (Poulsen et al ., ), the potential high‐discharge sites identified by this set of metrics and constraints indicate locations of potential high‐groundwater discharge as opposed to the diffuse discharge through the rest of the channel.…”

Section: Methodssupporting

confidence: 57%

Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio‐temporal variability of groundwater discharge in soft‐bedded streams

Sebok

Duque

Engesgaard

et al. 2015

Hydrological Processes

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The delineation of groundwater discharge areas based on Distributed Temperature Sensing (DTS) data of the streambed can be difficult in soft‐bedded streams where sedimentation and scouring processes constantly change the position of the fibre optic cable relative to the streambed. Deposition‐induced temperature anomalies resemble the signal of groundwater discharge while scouring will cause the cable to float in the water column and measure stream water temperatures. DTS applied in a looped layout with nine fibre optic cable rows in a 70 × 5 m section of a soft‐bedded stream made it possible to detect variability in streambed temperatures between October 2011 and January 2012. Detailed monthly streambed elevation surveys were carried out to monitor the position of the fibre optic cable relative to the streambed and to quantify the effect of sedimentation processes on streambed temperatures. Based on the simultaneous interpretation of streambed temperature and elevation data, a method is proposed to delineate potential high‐groundwater discharge areas and identify deposition‐induced temperature anomalies in soft‐bedded streams. Potential high‐discharge sites were detected using as metrics the daily minimum, maximum and mean streambed temperatures as well as the daily amplitude and standard deviation of temperatures. The identified potential high‐discharge areas were mostly located near the channel banks, also showing temporal variability because of the scouring and redistribution of streambed sediments, leading to the relocation of pool‐riffle sequences. This study also shows that sediment deposits of 0.1 m thickness already resulted in an increase in daily minimum streambed temperatures and decrease in daily amplitude and standard deviation. Scouring sites showed lower daily minimum streambed temperatures and higher daily amplitude and standard deviation compared with areas without sedimentation and scouring. As a limitation of the approach, groundwater discharge occurring at depositional and scouring areas cannot be identified by the metrics applied. Copyright © 2015 John Wiley & Sons, Ltd.

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Section: Methodssupporting

confidence: 57%

Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio‐temporal variability of groundwater discharge in soft‐bedded streams

Sebok

Duque

Engesgaard

et al. 2015

Hydrological Processes

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“…This would decrease the calculated flow accretion at 04. It is shown that there is substantial difference in spatial and temporal groundwater seepage both across‐ and along the stream (Karan et al ; Poulsen et al ). Therefore, because the flux is calculated from a synchronous campaign, it is also likely that the vertical flux does not coincide with long‐term temperature monitoring trends at the site.…”

Section: Discussionmentioning

confidence: 99%

Air/water/sediment temperature contrasts in small streams to identify groundwater seepage locations

2017

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The need to identify groundwater seepage locations is of great importance for managing both stream water quality and groundwater sourced ecosystems due to their dependency on groundwater‐borne nutrients and temperatures. Although several reconnaissance methods using temperature as tracer exist, these are subjected to limitations related to mainly the spatial and temporal resolution and/or mixing of groundwater and surface water leading to dilution of the temperature differences. Further, some methods, for example, thermal imagery and fiber optic distributed temperature sensing, although relative efficient in detecting temperature differences over larger distances, these are labor‐intensive and costly. Therefore, there is a need for additional cost‐effective methods identifying substantial groundwater seepage locations. We present a method expanding the linear regression of air and stream temperatures by measuring the temperatures in dual‐depth; in the stream column and at the streambed‐water interface (SWI). By doing so, we apply metrics from linear regression analysis of temperatures between air/stream and air/SWI (linear regression slope, intercept, and coefficient of determination), and the daily water temperature cycle (daily mean temperatures, temperature variance, and the mean diel temperature fluctuation). We show that using metrics from only single‐depth stream temperature measurements are insufficient to identify substantial groundwater seepage locations in a head‐water stream. Conversely, comparing the metrics from dual‐depth temperatures show significant differences; at groundwater seepage locations, temperatures at the SWI merely explain 43–75% of the variation opposed to ⩾ 91% at the corresponding stream column temperatures. In general, at these locations at the SWI, the slopes ( < 0.25) and intercepts ( > 6.5 °C) are substantially lower and higher, respectively, while the mean diel temperature fluctuations ( < 0.98 °C) are decreased compared to remaining locations. The dual‐depth approach was applied in a post‐glacial fluvial setting, where metrics analyses overall corroborated with field measurements of groundwater fluxes and stream flow accretions. Thus, we propose a method reliably identifying groundwater seepage locations along streambeds in such settings.

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“…We measured high 3.0 L min −1 flux PFP seeps with a seepage meter. Despite the very few locations of PFPs, their high fluxes have the potential to contribute significantly to the groundwater gain across the site (Poulsen et al, 2015). The peat thickness map (Fig.…”

Section: Thermal Evaluation Of Groundwater Seepagementioning

confidence: 99%

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

Hare

Boutt

Clement

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. Peatland environments provide important ecosystem services including water and carbon storage, nutrient processing and retention, and wildlife habitat. However, these systems and the services they provide have been degraded through historical anthropogenic agricultural conversion and dewatering practices. Effective wetland restoration requires incorporating site hydrology and understanding groundwater discharge spatial patterns. Groundwater discharge maintains wetland ecosystems by providing relatively stable hydrologic conditions, nutrient inputs, and thermal buffering important for ecological structure and function; however, a comprehensive site-specific evaluation is rarely feasible for such resource-constrained projects. An improved process-based understanding of groundwater discharge in peatlands may help guide ecological restoration design without the need for invasive methodologies and detailed sitespecific investigation.Here we examine a kettle-hole peatland in southeast Massachusetts historically modified for commercial cranberry farming. During the time of our investigation, a large process-based ecological restoration project was in the assessment and design phases. To gain insight into the drivers of site hydrology, we evaluated the spatial patterning of groundwater discharge and the subsurface structure of the peatland complex using heat-tracing methods and groundpenetrating radar. Our results illustrate that two groundwater discharge processes contribute to the peatland hydrologic system: diffuse lower-flux marginal matrix seepage and discrete higher-flux preferential-flow-path seepage. Both types of groundwater discharge develop through interactions with subsurface peatland basin structure, often where the basin slope is at a high angle to the regional groundwater gradient. These field observations indicate strong correlation between subsurface structures and surficial groundwater discharge. Understanding these general patterns may allow resource managers to more efficiently predict and locate groundwater seepage, confirm these using remote sensing technologies, and incorporate this information into restoration design for these critical ecosystems.

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Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream: combining hydraulic and tracer methods

Cited by 35 publications

References 66 publications

Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio‐temporal variability of groundwater discharge in soft‐bedded streams

Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio‐temporal variability of groundwater discharge in soft‐bedded streams

Air/water/sediment temperature contrasts in small streams to identify groundwater seepage locations

Hydrogeological controls on spatial patterns of groundwater discharge in peatlands

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