Groundwater discharge to wetlands driven by storm and flood events: Quantification using continuous Radon-222 and electrical conductivity measurements and dynamic mass-balance modelling

Gilfedder, Benjamin; Frei, Sven; Hofmann, Harald; Cartwright, Ian

doi:10.1016/j.gca.2015.05.037

Cited by 64 publications

(39 citation statements)

References 39 publications

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“…In addition, 222 Rn equilibrium assumption can be influenced by storm events (Gilfedder et al . , ). Sampling did not occur just after heavy rain or high wind events; therefore, we assumed that this would not significantly influence our results, especially the yearly ones.…”

Section: Discussionmentioning

confidence: 97%

“…The two tracers are clearly complementary, and their combined application improves our understanding and confidence in the overall results. In addition, 222 Rn equilibrium assumption can be influenced by storm events (Gilfedder et al, 2015). Sampling did not occur just after heavy rain or high wind events; therefore, we assumed that this would not significantly influence our results, especially the yearly ones.…”

Section: Methodological Limitationsmentioning

confidence: 99%

“…() and led to many subsequent applications (Cook et al . , ; Gilfedder, Frei, Hofmann, & Cartwright, ; Gleeson, Novakowski, Cook, & Kyser, ; Kluge et al . , ; Kluge et al .…”

Section: Introductionmentioning

confidence: 99%

“…However, the use of 222 Rn in lakes has only gained attention in recent years, probably due to generally low 222 Rn activity in lakes (in the range of a few Bq/m 3 ), in contrast to the high activity in groundwater (typically between 1,000 and 100,000 Bq/m 3 ). The first lake water budget based on 222 Rn was demonstrated by Corbett et al (1997) and led to many subsequent applications (Cook et al, 2008;Gilfedder, Frei, Hofmann, & Cartwright, 2015;Gleeson, Novakowski, Cook, & Kyser, 2009;Kluge et al, 2007;Kluge et al, 2012;Malgrange & Gleeson, 2014). For simplicity, most studies assumed constant 222 Rn activity for the whole water column and disregarded vertical gradients related to lake stratification, although these are widely known to potentially be informative (Cook et al, 2008;Schmidt & Schubert, 2007).…”

mentioning

confidence: 99%

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Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Arnoux

Gibert-Brunet

Barbecot

et al. 2017

Hydrological Processes

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Interactions between lakes and groundwater are of increasing concern for freshwater environmental management but are often poorly characterized. Groundwater inflow to lakes, even at low rates, has proven to be a key in both lake nutrient balances and in determining lake vulnerability to pollution. Although difficult to measure using standard hydrometric methods, significant insight into groundwater–lake interactions has been acquired by studies applying geochemical tracers. However, the use of simple steady‐state, well‐mixed models, and the lack of characterization of lake spatiotemporal variability remain important sources of uncertainty, preventing the characterization of the entire lake hydrological cycle, particularly during ice‐covered periods. In this study, a small groundwater‐connected lake was monitored to determine the annual dynamics of the natural tracers, water stable isotopes and radon‐222, through the implementation of a comprehensive sampling strategy. A multilayer mass balance model was found outperform a well‐mixed, one‐layer model in terms of quantifying groundwater fluxes and their temporal evolution, as well as characterizing vertical differences. Water stable isotopes and radon‐222 were found to provide complementary information on the lake water budget. Radon‐222 has a short response time, and highlights rapid and transient increases in groundwater inflow, but requires a thorough characterization of groundwater radon‐222 activity. Water stable isotopes follow the hydrological cycle of the lake closely and highlight periods when the lake budget is dominated by evaporation versus groundwater inflow, but continuous monitoring of local meteorological parameters is required. Careful compilation of tracer evolution throughout the water column and over the entire year is also very informative. The developed models, which are suitable for detailed, site‐specific studies, allow the quantification of groundwater inflow and internal dynamics during both ice‐free and ice‐covered periods, providing an improved tool for understanding the annual water cycle of lakes.

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Section: Discussionmentioning

confidence: 97%

Section: Methodological Limitationsmentioning

confidence: 99%

“…() and led to many subsequent applications (Cook et al . , ; Gilfedder, Frei, Hofmann, & Cartwright, ; Gleeson, Novakowski, Cook, & Kyser, ; Kluge et al . , ; Kluge et al .…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Arnoux

Gibert-Brunet

Barbecot

et al. 2017

Hydrological Processes

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“…RMBs assume equilibrium over time between radon ( 222 Rn) inputs and Rn losses and are a common approach for determining LGD rates to surface water bodies such as lakes, rivers, or the sea (Burnett & Dulaiova, 2003;Dimova & Burnett, 2011;Gilfedder, Frei, Hofmann, & Cartwright, 2015;Schmidt et al, 2008). After accounting for all radon sources and sinks within the considered system, the residual Rn flux [Bq·m −2 ·day −1 ] that is required for mass balancing is attributed to LGD.…”

Section: Radon Mass Balancementioning

confidence: 99%

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (¹⁸O, ²H) and radon (²²²Rn) mass balances

Petermann

Gibson

Knöller

et al. 2018

Hydrological Processes

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Lacustrine groundwater discharge (LGD) and the related water residence time are crucial parameters for quantifying lake matter budgets and assessing its vulnerability to contaminant input. Our approach utilizes the stable isotopes of water (δ18O, δ2H) and the radioisotope radon (222Rn) for determining long‐term average and short‐term snapshots in LGD. We conducted isotope balances for the 0.5‐km2 Lake Ammelshainer See (Germany) based on measurements of lake isotope inventories and groundwater composition accompanied by good quality and comprehensive long‐term meteorological and isotopic data (precipitation) from nearby monitoring stations. The results from the steady‐state annual isotope balances that rely on only two sampling campaigns are consistent for both δ18O and δ2H and suggested an overall long‐term average LGD rate that was used to infer the water residence time of the lake. These findings were supported by the good agreement of the simulated LGD‐driven annual cycles of δ18O and δ2H lake inventories with the observed lake isotope inventories. However, radon mass balances revealed lower values that might be the result of seasonal LGD variability. For obtaining further insights into possible seasonal variability of groundwater–lake interaction, stable water isotope and radon mass balances could be conducted more frequently (e.g., monthly) in order to use the derived groundwater discharge rates as input for time‐variant isotope balances.

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FINIFLUX: An implicit finite element model for quantification of groundwater fluxes and hyporheic exchange in streams and rivers using radon

Frei

Gilfedder

2015

Water Resources Research

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A quantitative understanding of groundwater-surface water interactions is vital for sustainable management of water quantity and quality. The noble gas radon-222 (Rn) is becoming increasingly used as a sensitive tracer to quantify groundwater discharge to wetlands, lakes, and rivers: a development driven by technical and methodological advances in Rn measurement. However, quantitative interpretation of these data is not trivial, and the methods used to date are based on the simplest solutions to the mass balance equation (e.g., first-order finite difference and inversion). Here we present a new implicit numerical model (FINIFLUX) based on finite elements for quantifying groundwater discharge to streams and rivers using Rn surveys at the reach scale (1-50 km). The model is coupled to a state-of-the-art parameter optimization code Parallel-PEST to iteratively solve the mass balance equation for groundwater discharge and hyporheic exchange. The major benefit of this model is that it is programed to be very simple to use, reduces nonuniqueness, and provides numerically stable estimates of groundwater fluxes and hyporheic residence times from field data. FINIFLUX was tested against an analytical solution and then implemented on two German rivers of differing magnitude, the Salzach ($112 m 3 s 21 ) and the Rote Main ($4 m 3 s 21 ). We show that using previous inversion techniques numerical instability can lead to physically impossible negative values, whereas the new model provides stable positive values for all scenarios. We hope that by making FINIFLUX freely available to the community that Rn might find wider application in quantifying groundwater discharge to streams and rivers and thus assist in a combined management of surface and groundwater systems.

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Groundwater discharge to wetlands driven by storm and flood events: Quantification using continuous Radon-222 and electrical conductivity measurements and dynamic mass-balance modelling

Cited by 64 publications

References 39 publications

Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (¹⁸O, ²H) and radon (²²²Rn) mass balances

FINIFLUX: An implicit finite element model for quantification of groundwater fluxes and hyporheic exchange in streams and rivers using radon

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Groundwater discharge to wetlands driven by storm and flood events: Quantification using continuous Radon-222 and electrical conductivity measurements and dynamic mass-balance modelling

Cited by 64 publications

References 39 publications

Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Interactions between groundwater and seasonally ice‐covered lakes: Using water stable isotopes and radon‐222 multilayer mass balance models

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (18O, 2H) and radon (222Rn) mass balances

FINIFLUX: An implicit finite element model for quantification of groundwater fluxes and hyporheic exchange in streams and rivers using radon

Contact Info

Product

Resources

About

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (¹⁸O, ²H) and radon (²²²Rn) mass balances