Evaluating long-term patterns of decreasing groundwater discharge through a lake-bottom permeable reactive barrier

Science of The Total Environment

Wang

Day‐Lewis

et al. 2019

Self Cite

River to floodplain hydrologic connectivity is strongly enhanced by beaver-(Castor canadensis) engineered channel water diversions. The hydroecological impacts are wide ranging and generally positive, however, the hydrogeochemical characteristics of beaver-induced flowpaths have not been thoroughly examined. Using a suite of complementary ground-and drone-based heat tracing and remote sensing methodology we characterized the physical template of beaver-induced floodplain exchange for two alluvial mountain streams near Crested Butte, Colorado, USA. A flowpath-oriented perspective to water quality sampling allowed characterization of the chemical evolution of channel water diverted through floodplain beaver ponds and ultimately back to the channel in 'beaver pond return flows'. Return seepages were universally suboxic, while ponds and surface return flows showed a range of oxygen concentration due to in-situ photosynthesis and atmospheric mixing. Median concentrations of reduced metals: manganese (Mn), iron (Fe), aluminum (Al), and arsenic (As) were substantially higher along beaver-induced flowpaths than in geologically controlled seepages and upstream main channel locations. The areal footprint of reduced return flow seepage flowpaths were imaged with surface electromagnetic methods, indicating extensive zones of high-conductivity 2 2 shallow groundwater flowing back toward the main channels and emerging at relatively warm bank seepage zones observed with infrared. Multipledepth redox dynamics within one focused seepage zones showed coupled variation over time, likely driven by observed changes in seepage rate that may be driven by pond stage. High-resolution times series of dissolved Mn and Fe collected downstream of the beaver-impacted reaches indicated seasonal dynamics in mixed river metal concentrations. Al time series concentrations showed proportional change to Fe at the smaller stream location, indicating chemically reduced flowpaths were sourcing Al to the channel. Overall our results indicated beaver-induced floodplain exchanges create important, and perhaps dominant, transport pathways for floodplain metals by expanding chemically-reduced zones paired with strong advective exchange.

Section: Metal Oxide Deposition At Beaver Pond Return Flowsmentioning

confidence: 99%

Return flows from beaver ponds enhance floodplain-to-river metals exchange in alluvial mountain catchments

Science of The Total Environment

Wang

Day‐Lewis

et al. 2019

Self Cite

“…Because thermal infrared sensing does not penetrate the water surface, submerged discharge zones were identified using a handheld thermocouple temperature probe (Digi‐Sense, Inc) inserted 0.1 m into the streambed at approximate 20‐m longitudinal intervals where the stream was wadable. A temperature reading was recorded for each streambed point after a 1‐min stabilization period following the procedures of McCobb et al (2018), who found that cold summer lakebed temperatures were indicative of preferential groundwater discharge to a nearby kettle lake.…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, stable water isotopes collected in discharge zones can indicate the seasonality of source recharge and whether source flowpaths are local to the river corridor or more regional (Springer, Boldt, & Junghans, 2017). In this study, we integrate imaging of streambank discharges with thermal infrared cameras (e.g., Handcock et al, 2012), push‐probe streambed temperature measurements (e.g., McCobb, Briggs, LeBlanc, Day‐Lewis, & Johnson, 2018), and previously collected fibre‐optic distributed temperature data (e.g., Rosenberry, Briggs, Delin, & Hare, 2016) to guide sampling of discharging groundwater for geochemical, gas, isotopic, and PFAS analysis along 6 km of a coastal stream. The stream is home to an important managed native brook trout population, and we build directly on recent research from the same stream system showing that trout tend to favour local, oxygen‐rich groundwater discharges at the base of near‐channel hillslopes for spawning (Briggs, Harvey, et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Hillslope groundwater discharges provide localized stream ecosystem buffers from regional per‐ and polyfluoroalkyl substances contamination

Tokranov

Hull

et al. 2020

Hydrological Processes

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Emerging groundwater contaminants such as per-and polyfluoroalkyl substances (PFAS) may impact surface-water quality and groundwater-dependent ecosystems of gaining streams. Although complex near-surface hydrogeology of stream corridors challenges sampling efforts, recent advances in heat tracing of discharge zones enable efficient and informed data collection. For this study, we used a combination of streambed temperature push-probe and thermal infrared methods to guide a discharge-zone-oriented sample collection along approximately 6 km of a coastal trout stream on Cape Cod, MA. Eight surface-water locations and discharging groundwater from 24 streambed and bank seepages were analysed for dissolved oxygen (DO), specific conductance, stable water isotopes, and a range of PFAS compounds, which are contaminants of emerging concern in aquatic environments. The results indicate a complex system of groundwater discharge source flowpaths, where the sum of concentrations of six PFAS compounds (corresponding to the U.S. Environmental Protection Agency third Unregulated Contaminant Monitoring Rule "UCMR 3") showed a median concentration of 52 ± 331 (SD) ng/L with two higher outliers and three discharges with PFAS concentrations below the quantification limit. Higher PFAS concentration was related (−0.66 Spearman rank, p < .001) to discharging groundwater that showed an evaporative signature (deuterium excess), indicating flow through at least one upgradient kettle lake. Therefore, more regional groundwater flowpaths originating from outside the local river corridor tended to show higher PFAS concentrations as evaluated at their respective discharge zones. Conversely, PFAS concentrations were typically low at discharges that did not indicate evaporation and were adjacent to steep hillslopes and, therefore, were classified as locally recharged groundwater. Previous research at this stream found that the native brook trout spawn at discharge points of groundwater recharged on local hillslopes, likely in response to generally higher levels of DO. Our study shows that by targeting high oxygen discharges the trout may thereby be avoiding emerging contaminants such as PFAS in groundwater recharged farther from the stream.

“…Groundwater discharge influences stream biogeochemistry (Boulton, Findlay, Marmonier, Stanley, & Valett, 1998;Caissie, Kurylyk, St-Hilaire, El-Jabi, & MacQuarrie, 2014;Schmidt, Conant, Bayer-Raich, & Schirmer, 2007) and maintains steady and spatially diverse stream temperatures, providing thermal refugia for aquatic species (Anibas et al, 2009;Boulton et al, 1998;Brunke & Gonser, 1997;Kurylyk, MacQuarrie, Linnansaari, Cunjak, & Curry, 2015;McCobb, Briggs, LeBlanc, Day-Lewis, & Johnson, 2018;Wondzell, 2011).…”

Section: Introductionmentioning

confidence: 99%

Quantitative guidance for efficient vertical flow measurements at the sediment–water interface using temperature–depth profiles

Irvine

Kurylyk

2019

Hydrological Processes

Self Cite

Upward discharge to surface water bodies can be quantified using analytical models based on temperature-depth (T-z) profiles. The use of sediment T-z profiles is attractive as discharge estimates can be obtained using point-in-time data that are collected inexpensively and rapidly. Previous studies have identified that T-z methods can only be applied at times of the year when there is significant difference between the streambed-water interface and deeper sediment temperatures (e.g., winter and summer). However, surface water temperatures also vary diurnally, and the influence of these variations on discharge estimates from T-z methods is poorly understood.For this study, synthetic T-z profiles were generated numerically using measured streambed interface temperature data to assess the influence of diurnal temperature variations on discharge estimation and provide insight into the suitable application of T-z methods. Results show that the time of day of data collection can have a substantial influence on vertical flux estimates using T-z methods. For low groundwater discharge fluxes (e.g., 0.1 m d −1 ), daily transience in streambed temperatures led to relatively large errors in estimated flow magnitude and direction. For higher discharge fluxes (1.5 m d −1 ), the influence of transient streambed temperatures on discharge estimates was strongly reduced. Discharge estimates from point-in-time T-z profiles were most accurate when the uppermost point in the T-z profile was near the bed interface daily mean (two time periods daily). Where temperature time series data are available, daily averaged T-z profiles can produce accurate discharge estimates across a wide range of discharge rates. Seasonality in shallow groundwater temperature generally had a negligible influence on vertical flow estimates. These findings can be used to plan field campaigns and provide guidance on the optimal applicationof T-z methods to quantify vertical groundwater discharge to surface water bodies. K E Y W O R D Sanalytical solutions, gaining stream, groundwater discharge, groundwater, surface water exchange, heat as a groundwater tracer, hyporheic flow, river-aquifer interactions, streambed mapping