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

Abstract

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.

Quantifying flood-water impacts on a lake water budget via volume-dependent transient stable isotope mass balance

“…Finally, in late January 2018, the isotopic composition of Lake A was found to be relatively homogenous throughout the water column. This is likely the result of autumnal turnover (Arnoux et al, 2017b). Note that, the isotopic composition is slightly less enriched in heavy isotopes than during the previous winter (i.e., -10.86 ‰ to -10.23 ‰).…”

“…i.e., that they experience turnover of the water column in spring and late autumn. Arnoux et al (2017b) observed that the spring mixing occurs from mid-May to early June at Lake Lacasse (approximately 80 km NW of the study site). Hence, Lake A likely went through a turnover of its water column during the same period.…”

Anthropic and Meteorological Controls on the Origin and Quality of Water at a Bank Filtration Site in Canada

“…Higher EC at greater depth could be induced by regional groundwater inputs into Lake B. In Canada, groundwater inputs are typically found at the bottom of lakes, due to thermal (and density) contrast [47]. Smaller vertical variability was observed in wintertime (in comparison to summertime).…”

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

“…This tremendous offset cannot be readily explained by spatial or temporal variability. The differences also highlight the inherent sensitivity of the approach to the definition of the endmember concentrations, an issue also raised by Arnoux, Barbecot, et al () and Arnoux, Gibert‐Brunet, et al (). We considered the actual measurement of Rn in groundwater as more representative for the Rn groundwater endmember because the thickness of the lake bottom sediment layer is only a few centimetres in the littoral zone (Schmidt et al, ) where the majority of LGD is expected to occur.…”

“…Stable isotopes of water (J. J. Gibson, Birks, & Yi, ; J. J. Gibson, Birks, Yi, Moncur, & McEachern, ; Hofmann, Knöller, & Lessmann, ; Knöller et al, ; Knöller & Strauch, ; Krabbenhoft, Anderson, & Bowser, ) and the radioisotope radon (Corbett, Burnett, Cable, & Clark, ; Dimova & Burnett, ; Schmidt, Stringer, Haferkorn, & Schubert, ) or a combination of both (Arnoux, Barbecot, et al, ; Arnoux, Gibert‐Brunet, et al, ; Schmidt, Gibson, Santos, Schubert, & Tattrie, ) are well‐established in groundwater–lake interaction studies. For instance, Luo, Jiao, Wang, and Liu () and Dimova and Burnett () reported on significant temporal variation of LGD on a multi‐day timescale based on radon for a Chinese desert lakes and small lakes in central Florida (United States), respectively.…”